An Optical Survey of the Partially Embedded Young Cluster in NGC 7129
aa r X i v : . [ a s t r o - ph . S R ] M a r An Optical Survey of the Partially Embedded Young Cluster inNGC 7129
S. E. Dahm and L. A. Hillenbrand ABSTRACT
NGC 7129 is a bright reflection nebula located in the molecular cloud complex near l =105 . ◦ b =+9 . ◦
9, about 1.15 kpc distant. Embedded within the reflection nebula is a young clusterdominated by a compact grouping of four early-type stars: BD+65 ◦ ◦ α
234 (B8e). About 80 H α emission sources brighter than V ∼ V ∼ V R C I C ) photometry of a field centered on the reflectionnebula and spectral types for more than 130 sources determined from low dispersion, opticalspectroscopy. The narrow pre-main sequence evident in the color-magnitude diagram suggeststhat star formation was rapid and coeval. A median age of about 1.8 Myr is inferred for theH α and literature-identified X-ray emission sources having established spectral types, using pre-main sequence evolutionary models. Our interpretation of the structure of the molecular cloudand the distribution of young stellar objects is that BD+65 ◦ α
234 and several embeddedsources evident in near infrared adaptive optics imaging have formed recently within the ridgeof compressed molecular gas. The compact cluster of low-mass stars formed concurrently withthe early-type members, concentrated within a central radius of ∼ ∼ ◦ ◦ α Subject headings: stars: formation, pre-main sequence - Galaxy: open clusters and associations: individ-ual(NGC 7129)
1. Introduction
The bright reflection nebula NGC 7129 ( l =105 ◦ , b =+9 . ◦
9) is illuminated by the early-typemembers of a young stellar cluster emerging froma molecular cloud complex composed of the darknebulae Lynds 1181 (L1181), L1183, and TDS395 (Taylor et al. 1987; Yonekura et al. 1997).Signatures of star formation activity are presentthroughout the region including two dozen Herbig-Haro (HH) objects, two large molecular outflows,numerous nebulous filaments, and embedded in-frared sources. The cluster is dominated by W. M. Keck Observatory, Kamuela, HI 96743 California Institute of Technology a tight grouping of B-type stars that includesBD+65 ◦ ◦ α
234 (B8e).An elongated cavity one parsec in diameter hasbeen carved out of L1181, presumably by the stel-lar winds and ultraviolet flux emanating from thecentral grouping of B-stars. Shown in Figure 1is a three-color (
V R C I C -band) image of the re-flection nebula obtained by G. H. Herbig in 1999October using the University of Hawaii (UH) 2.2m telescope on Mauna Kea. The image clearlydepicts the dense molecular ridge to the east andsouth, the evacuated region around the four lumi-nous central stars, and the emerging young clusterlying within the reflection nebula. The distance of1GC 7129 was estimated to be ∼ CO and CO surveys have identified multi-ple density enhancements in the region, a semi-circular ridge of CO emission to the north, east,and south of the reflection nebula, and the largeevacuated cavity centered near BD+65 ◦ µ m sources in the area: LkH α
234 and far infraredsource 2 (FIRS 2), which has no optical coun-terpart, located some 2 ′ south of BD+65 ◦ α ∼ ⊙ .A single-channel 2.2 µ m survey of the regionwas carried out by Strom et al. (1976), here-after SVS, in a search for an embedded popula-tion of newly formed stars. Although none wereidentified, the detection limit of the survey wasmarginally close to the expected brightness of anaverage T Tauri star. Cohen & Schwartz (1983)identified four new infrared sources in the region,one of which was V350 Cep, an M2-type T Tauristar that brightened dramatically between 1970and 1976. Ibryamov et al. (2014) present a photo-metric study for this source that includes a long-term light curve constructed from archival data.Gutermuth et al. (2004) used the Two MicronAll Sky Survey (2MASS), the FLAMINGOS spec-trograph on the Multiple Mirror Telescope, andthe Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope to complete an extensive1.2 to 8.0 µ m survey of the cluster, ultimately de-termining a disk fraction of 54 ±
14% within the cluster core (defined as a 0.5 pc radius arc ex-tending from the peak of the local stellar surfacedensity). From a star count analysis, Gutermuthet al. (2004) estimate that there are about 80 clus-ter members within the core, down to a limitingmagnitude of K S =16 mag, or approximately 0.055M ⊙ for unattenuated sources. In the peripheralareas Gutermuth et al. (2004) estimate that theextended cluster population is roughly equal tothat of the core.Muzerolle et al. (2004) present 24 µ m Multi-band Imaging Photometer for Spitzer (MIPS)imaging of NGC 7129 and provide a census of thecluster population outside of the reflection neb-ula. Of the 36 sources detected at 24 µ m and inat least three IRAC passbands, 13 were classifiedas Class 0/I protostars with envelopes includingFIRS 2 (Class 0), another 18 as Class II sources(classical T Tauri stars, CTTS) with relatively lowinfrared luminosity, and six were classified as ClassIII sources with emission consistent with that ofpure stellar photospheres. The majority of thesesources are located in an arc sweeping north-eastto south of the reflection nebula, effectively trac-ing the densest regions of the remnant molecularcloud. Muzerolle et al. (2004) conclude that starformation is not concentrated in the cluster core,but rather dispersed over a substantial area, some ∼ Spitzer surveys of Gutermuth et al. (2004)and Muzerolle et al. (2004) with a shallow 22 ks
Chandra
Advanced CCD Imaging Spectrometer(ACIS) X-ray observation of the region. From the
Spitzer infrared excess sources and the 59
Chandra
X-ray detections, they define a sample of 26 ClassII and 25 Class III cluster members, estimated tobe complete to ∼ ⊙ . The disk fraction ofthe least biased sub-sample composed of lightlyextincted sources is ∼ +24 − %.While NGC 7129 has been studied extensivelyat millimeter, micron, and X-ray wavelengths,it remains poorly characterized in the optical.Hartigan & Lada (1985) obtained V R C I C andnarrowband H α CCD imaging of two regions inNGC 7129 which include most sources from theinfrared surveys of Cohen & Schwartz (1983) andSVS.
V R C I C photometry is provided for about 30sources in these two fields. Magakian et al. (2004)identified 22 H α emission stars in the central and2ortheast cluster regions, complete to V ∼
20 us-ing slitless spectroscopy.
V RI − band photometryfor about 100 sources was also obtained, but notprovided in the published analysis. Magakian etal. (2004) concluded that most of the detected H α emission sources were T Tauri stars. Vilnius 7-color photometry down to V =18.8 is provided byStraiˇzys et al. (2014) for 159 stars in the clusterregion. The photometric data was used to clas-sify about half of the detected sources, assign-ing spectral types, luminosity classes and deriv-ing extinction estimates. The extinction across a23 ′ × ′ area varies between 0.6 and 2.8 mag, butin the densest parts of the molecular cloud, A V approaches ∼
13 mag. Straiˇzys et al. (2014) deter-mine the age of the cluster to be between 0.2 and 3Myr by plotting six early-type cluster members onthe HR diagram and using the evolutionary mod-els of Palla (2005).From the literature described above, some 90pre-main sequence candidates have been identi-fied in the cluster region spanning an area ∼ ′ in diameter or ∼ α emission (Hartigan &Lada 1985; Magakian et al. 2004), X-ray emis-sion (Stelzer & Scholz 2009), and infrared excess(Gutermuth et al. 2004; Muzerolle et al. 2004;Stelzer & Scholz 2009). No comprehensive opticalphotometric and spectroscopic census of the youngcluster population, however, has been published todate.In this paper we present deep ( V ∼ V R C I C − band photometry for a field roughly cen-tered on the reflection nebula. Results from aslitless grism, H α spectroscopic survey of a ∼ ∼
130 stars in theregion, determined from low-dispersion, multi-object spectroscopy. We also present high disper-sion (R ∼ ◦ ◦ α α
234 is examined and compared witharchived
Spitzer
IRAC data.This paper is organized as follows: in Section2 we discuss the observations made by the au-thors and by G. H. Herbig in support of this in-vestigation. In Section 3 we present the high-dispersion spectra of the early-type stars and of V350 Cep; in Section 4 the stellar population ofNGC 7129 is examined to include the early-typestars, the H α emission sources, and the X-ray de-tected sources. We present in tabular form pho-tometry and spectral types determined at opticalwavelengths for two subsets of stars: 1) those ex-hibiting H α and/or X-ray emission, and 2) othersin the field, some of which exhibit infrared excess.In Section 5 we discuss the color-magnitude di-agram of the pre-main sequence population, theaverage extinction suffered by those stars with as-signed spectral types, the ages and masses of thecluster members, and the infrared color-color dia-grams. In Section 6 we discuss the progression ofstar formation in the parent molecular clouds aswell as the star forming history in the region. Weexamine the source of the molecular outflow nearLkH α
234 and the origin of the photo-dissociationregion enveloping the early-type stars.
2. Observations2.1. Optical Photometry
Three epochs of optical imaging data were ob-tained of the NGC 7129 region between 1993 and1999. Extinction corrections and transformationto the Landolt (1992) system were achieved forall three sets by observing several standard fieldsperiodically throughout the night at various airmasses. The photometric calibrations includedzero point, airmass, and color terms except whenindicated below.The first and most extensive survey consistedof
V R C I C − band CCD imaging obtained using theT2KA CCD at the Kitt Peak National Observa-tory (KPNO) 0.9m telescope in 1993 June by LAHand S. Strom. The T2KA detector is a 2048 × µ m pixels yielding a platescale of0 . ′′
69 pixel − . Twilight flats were obtained at thebeginning and end of the nights in all filters toremove pixel to pixel variations in response. Ex-posure times were 3, 30 and 300 s in all passbands.The optical images span a region 23 ′ × ′ in areawith a photometric completeness limit of V ∼ ′ × ′ red Digitized Sky Survey (DSS) im-age of the region shown in Figure 2. The T2KACCD images were reduced using standard tasks3nd procedures available in the Image Reductionand Analysis Facility (IRAF). Point spread func-tion (PSF) fitting photometry was performed us-ing the DAOPHOT package of IRAF. The V − I C , V color-magnitude diagram for all ∼ V , V − R C , and R C − I C )photometry, and photometric errors for all ∼ R C I C − band photometrywas obtained using the Low Resolution ImagingSpectrograph (LRIS) on Keck II in 1999 June byLAH. The 8 ′ × ′ LRIS images were centered onLkH α
234 (Figure 2) and reveal dozens of faintcluster members within the compact grouping ofearly-type stars. Exposure times ranged from 3 to600 s to ensure that the majority of sources wereunsaturated. Tasks within the PHOT package ofIRAF were used to carry out aperture photometry.Photometric calibration was achieved using zeropoint and airmass terms only, i.e. no color termswere applied. Shown in Figure 3 (right panel) isthe R C − I C , R C color-magnitude diagram for allsources in the LRIS field of view with no allowancebeing made for interstellar reddening.Finally BV R C I C photometry of the NGC 7129region was obtained in 1999 October at the f/10focus of the UH 2.2 m telescope on Mauna Keaby G. H. Herbig. The detector was a Tektronix2048 × µ m pixels. The field wasimaged in all filters during photometric conditionsand in average seeing conditions for Mauna Kea,0 . ′′
75. The plate scale was 0 . ′′
22 pixel − , and theimaged field was approximately 7 . ′ × . ′ ∼ +0.16 mag) exists between the V − I C colorsof the 1999 October UH 2.2 m observations andthe 1993 June KPNO observations. This offsetoriginates from extended red transmission fromthe UH 2.2 m I C filter, which is documented byCourtois et al. (2011). Given the presence ofthis red leak in the UH 2.2 m I C filter, the opticalphotometry presented here is taken primarily fromthe 1993 KPNO observations, unless photometryfor a given source were not available. In thesecircumstances, the photometry from the 1999 UH2.2 m observations were substituted with a − . V − I C color.Differences in the R C - I C colors of the 1993 KPNOand the 1999 Keck LRIS data evident in Figure5 likely arise from the missing color term in thephotometric calibration of the latter data set. α Slitless Grism Spectroscopy
The H α emission survey of NGC 7129 was car-ried out on 10 October 2003 by SED using theWide-Field Grism Spectrograph (WFGS) installedat the f/10 Cassegrain focus of the University ofHawaii 2.2 m telescope. A 420 line mm − grismblazed at 6400˚A yielded a dispersion of 3.85˚Apixel − . The narrowband H α filter isolated aregion of the first-order spectra between ∼ × × ∼ . ′ × . ′ α Low-dispersion spectra were obtained usingHYDRA on WIYN in 1993 and the RC Spec-trograph on the Mayall 4 m telescope in 1994 byLAH. Spectra of earlier-type stars ( < K5) wereclassified using the standards of Allen & Strom(1995). The relative strengths of a number oftemperature sensitive features were adopted to in-clude the Na I D doublet, the Ca I absorption linesbetween 6100 and 6200˚A, the blend near H α , andthe Ca II near-infrared triplet, if in absorption.For late-type stars (K5 and later), the standards4f Kirkpatrick et al. (1993) and the temperaturesensitive TiO indices of Slesnick et al. (2006) andreferences therein were adopted. These indicesmeasure the strength of TiO absorption featuresnear λ λ High-dispersion optical spectra were obtainedby G. H. Herbig for BD+65 ◦ ◦ α
234 were obtained by LAH on 06 Dec1999 and by J. Kuhn on 13 Jun 2004. HIRESwas configured with the red cross-disperser andcollimator in beam for all observations presentedhere. The C1 decker (0 . ′′ × . ′′ ∼ ∼ − ). Near-complete spectralcoverage from ∼ × µ m pixels. The 1999 spectrum ofLkH α
234 used the D2 decker (1 . ′′ × . ′′
0) andcovers a range from 6240 to 8680 ˚A. The 2007observations of V350 Cep were made with the up-graded three-chip mosaic of MIT-LL CCDs having15 µ m pixels. The resulting spectral coverage ofthe 2007 observations of V350 Cep range from ap-proximately 4300 to 8600 ˚A. The CCDs were usedin low-gain mode, resulting in readout noise lev-els of ∼ − for the red, green,and blue detectors, respectively. Internal quartz lamps were used for flat fielding and ThAr lampspectra were obtained for wavelength calibration.Integration times were 120-1200s, yielding signal-to-noise levels of up to ∼
100 for the early-typestars. The cross-dispersed spectra were reducedand extracted using the Mauna Kea Echelle Ex-traction (MAKEE) pipeline written by T. Bar-low. Standard routines available through IRAFand IDL were used for spectral analysis. Theraw as well as pipeline extracted spectra for theHIRES observations presented here are availablethrough the Keck Observatory Archive (KOA):https://koa.ipac.caltech.edu. α High angular resolution, near infrared imagingof LkH α
234 was obtained with NIRC2 using thenatural guide star (NGS) adaptive optics systemon the Keck II telescope on 2012 June 30 by SED.The images were obtained with the wide cam-era (0 . ′′
04 pixel − platescale) in beam yielding a40 ′′ × ′′ field of view. A three position ditherwas used to image the field, avoiding the quadrantof the Alladin III detector that exhibits a higherlevel of fixed pattern noise. Integration times were10 s with 10 coadds in all three filters ( J, H, K ′ ),yielding an effective integration time of 100 s perframe. Basic image reduction and analysis werecompleted using standard routines written in IDL.
3. Analysis of the High Dispersion Spec-troscopy in the Context of Circumstel-lar Environments3.1. BD+65 ◦ BD+65 ◦ α emissionstar. Herbig (1960) found similar emission onplates obtained at Lick Observatory and classi-fied the star as B5n or earlier. Narrow emissioncomponents were present near the centers of allBalmer lines from H β through H δ and possiblyextending to H ǫ . Herbig (1960) also noted thatinterstellar Ca II was present and that the stellarspectrum was suggestive of an ordinary Be star.Other classifications for BD+65 ◦ β to be in5mission with no obvious P Cygni component andnoted that BD+65 ◦ I λ II λ ◦ ∼ B3, con-sistent with classifications found in the literature.The HIRES spectrum reveals strong H α emis-sion ( W = −
25 ˚A) with wings extending out to atleast ±
550 km s − . There is no indication of anunderlying, early-type stellar photosphere in theH α emission profile. The emission line is double-peaked as shown in Figure 7 with radial veloci-ties measured for the blue-shifted and red-shiftedcomponents of − − , respec-tively. The radial velocity of the core absorptionfeature is − − . These velocities differsubstantially from those found by Finkenzeller &Jankovics (1984), − − (core absorption)and −
36 and +45 km s − (blue and red emissionpeaks, respectively). H β , shown in Figure 7, re-veals a similar double-peaked emission structure,but is substantially weaker ( W = − β emission profileare − − , with the red emis-sion component having a higher amplitude thanthe blue component. Unlike the H α profile, broadabsorption wings are present in H β . H γ falls out-side the coverage of the HIRES spectrum, but thewing of its redward absorption edge is evident onthe bluest order. If H γ were in emission, it wouldbe expected to be weak.Other features of interest in the HIRES spec-trum of BD+65 ◦ I λ λ II emission), and broad, double-peaked emission profiles of Fe II λλ α and H β ). The Na I Dlines ( λλ ∼− − . In the local standard of rest, these veloci-ties are consistent with being produced within thelocal spiral arm, no more than 1 kpc distant usingthe galactic rotation curves calculated by M¨unch(1957). Diffuse interstellar bands (DIBs) are alsoevident in the spectrum near λλ ◦ II emission near select He I absorp-tion features. Alecian et al. (2013) determineda v sin i for BD+65 ◦ ±
27 km s − anda radial velocity of − ±
20 km s − , consistentwith the heliocentric radial velocity of the molec-ular cloud reported by Finkenzeller & Jankovics(1984), − − . Using a handful of He I absorption lines, we estimate the radial velocity ofBD+65 ◦ − − .Hillenbrand et al. (1992) classify BD+65 ◦ ◦ ◦ µ m, contrary to expectations if indeed disk-free. If confirmed, ´Abrah´am et al. (2000) suggestthat this 60 µ m emission could arise from colddust associated with the star. Lorenzetti et al.(2003) mapped NGC 7129 using the Long WaveSpectrometer onboard ISO in [O I] 63 and 145 µ mand in [C II] 158 µ m. The line emission is sugges-tive of two photodissociation regions (PDR), onebeing illuminated by BD+65 ◦ α Spitzer
MIPS 24 µ m sur-vey of the region, Muzerolle et al. (2004) reportthat while the photospheres of BD+65 ◦ ◦ ◦ BD+65 ◦ V = − .
0, somewhat more luminous than a nor-mal B3 zero age main sequence star. The slightlygreater distance adopted here would imply that6he star is even more luminous.Matthews et al. (2003) note that BD+65 ◦ II region and thatits temperature and luminosity place it near thebirthline of a ∼ ⊙ star using the evolutionarymodels of Palla & Stahler (1993). Matthews et al.(2003) assign a spectral type of B2.5 based upon1.4GHz continuum flux and the star’s estimatedexcitation parameter.The HIRES spectrogram of BD+65 ◦ I λ II λ α absorption profile shownin Figure 8. The centroid of this weak feature hasa velocity of about − − , which is con-sistent with the radial velocity of the molecularcloud. H β appears to be a normal absorption pro-file (Figure 8) as might be expected for an early-type stellar photosphere. No emission features at-tributed to Fe II are present in its spectrum aswith BD+65 ◦ α
234 (discussed be-low).The measured radial velocities for the interstel-lar Na I D lines are − − − ;comparable to those measured for BD+65 ◦ II λ I λλ ∼ +8.1 km s − . Given the large disparity inthe radial velocity of BD+65 ◦ ◦ ◦ α The luminous Herbig Be star LkH α
234 wasclassified by Herbig (1960) as having a late-A spec-tral type with strong H α emission and moderateintensity H β emission. Strom et al. (1972) clas-sify the star as B5-B7 and noted that H β and H γ were in emission with sharp P Cygni-like com-ponents. Possible weak emission was also notedfor He I λλ α I λ II λ α
234 is embedded within the ridge ofmolecular gas that defines the northeastern edgeof the evacuated cavity. From its placement abovethe zero age main sequence in the color-magnitudediagram, it is generally assumed that LkH α µ m and extending out beyond100 µ m.The HIRES spectra of LkH α
234 obtained in1999 and 2004 are suggestive of active accretionwith numerous metallic and forbidden transitionsin emission as well as H α and H β exhibiting com-plex emission structure. Shown in Figure 9 arethe H α profiles for LkH α
234 from 1999 and 2004.While of comparable strength ( W = − α profilespossess broad wings that extend several hundredkm s − from the central wavelength. The blue-ward side of the 2004 emission peak shows a dis-tinct, sharp drop-off that never declines below thecontinuum level (Figure 9). The H α profile is sug-gestive of a wind moving outward from the centralstar. This is supported by strong, blue-shifted [OI] λλ −
23 km s − , as well as blue-shifted [S II] λλ α I and Mg II absorption linesyield inconsistent results, possibly resulting fromsignificant stellar activity.Other prominent features in the spectrumof LkH α
234 include complex profiles of Fe II λλ I D lines exhibitnarrow and broad absorption components, theformer with radial velocities of about −
20 km s − (interstellar) and the latter, −
83 km s − . Shownin Figure 10 are the profiles of H β , Fe II λ I D lines in the 2004 HIRES spectrumof LkH α SVS 13 was previously unclassified in the liter-ature, but the high dispersion spectroscopy pre-sented here is suggestive of a mid- to-late B spec-tral type with very broad He I λλ β and H α are shown in Figure 11.While H β appears to be in pure absorption, H α reveals a broad absorption profile with a narrowemission core having a heliocentric radial velocityof −
23 km s − . Fe I λλ λ I D lines exhibit no trace of emission and thenarrow interstellar absorption components haveheliocentric radial velocities of ∼− − ,consistent with those found in the other early-typestars in the cluster. Diffuse interstellar bands arealso present near λλ µ m imag-ing to be completely saturated. The K − bandphotometry presented here was obtained with theSQIID camera on the KPNO 50-inch telescope in1993 (2MASS only provides a K S upper limit forthis source). The star’s placement in the near-infrared color-color diagrams to be discussed in § α emission evident in theHIRES spectrum would be consistent with that ofa Herbig Be star. The late-type (M2) pre-main sequence starV350 Cep lies near the edge of the L1181 molecu-lar cloud, ∼ . ′ α emission sources as well as thebright infrared source SVS 10. Herbig (2008) pro-vides an abridged history of V350 Cep observa-tions, which include that the source was unde-tected on the 1954 Palomar Sky Survey plates,but rose to its current brightness ( V ∼
16) some-time in the late 1960s or early 1970s. The sourceis clearly visible on plate 1 of SVS, a red photo-graph of NGC 7129 obtained using the Mayall 4m telescope at Kitt Peak. Pogosyants (1991) sug-gests that V350 Cep first exceeded the brightnesslimit ( V ∼ II emis-sion with an underlying M2-type photosphere, in-ferred from shallow absorption features in the redthought to arise from TiO bandheads. Hartigan &Lada (1985) conclude that V350 Cep illuminatesthe small reflection nebula GGD 33 and may be anoutflow source within the region. Goodrich (1986)obtained a low-resolution, spectrophotometric ob-servation of V350 Cep and noted strong Balmerline emission as well as a rich Fe II emission spec-trum.The HIRES spectrum of V350 Cep presentedhere is described briefly by Herbig (2008), whootherwise focuses his discussion on an earlier 2005spectrum, as exhibiting strong Balmer line emis-sion as well as metallic line emission. The promi-nent metal lines are evident throughout the spec-trum including Fe I λλ II λλ I emis-sion is present including λλ I D lines (Figure 12) exhibit broad emission withnarrow interstellar absorption components withintheir cores having radial velocities of −
18 km s − ,comparable to the velocities measured in the early-8ype stars. Broad Na I absorption features are alsoevident shifted some −
204 km s − blueward of therest wavelength. Herbig (2008) suggests that thesefeatures originate from the same outflowing ma-terial responsible for the P Cygni feature in H α .Similar radial velocities were reported by Herbig(2008) for these broadened absorption features.Forbidden emission, e.g. [O I] λ λ λ λ λ ∼ ∼ − ± − , consistent with thatmeasured by Herbig (1998) using the 2005 HIRESspectrum, − ± − .H α exhibits a strong P Cygni-like profile, W = − α hasedges of −
102 and −
252 km s , defined at thecontinuum level. Figure 12 shows the H α emis-sion profile with the velocities annotated for vari-ous features. This figure can be directly comparedwith that shown in Figure 9 of Herbig (2008) fromthe 2005 HIRES spectrum. The overall shape ofthe line profile has changed somewhat while theequivalent width decreased only slightly.Herbig (2008) concludes that V350 Cep is notan EXor candidate, i.e. a T Tauri-like star thatundergoes periodic flare-ups presumably as the re-sult of an inflow of material from the surroundingaccretion disk. Muzerolle et al. (2004) classifiedV350 Cep as a Class II source from its placementin the Spitzer [3.6] − [5.8], [8] − [24] color-color di-agram. While eliminated as an EXor candidate,V350 Cep is clearly undergoing significant accre-tion activity and is associated with a substantialcircumstellar disk as inferred from its strong H α emission and infrared excess. The nature of it dra-matic rise from obscurity is worthy of additionalstudy.
4. NGC 7129: The Cluster Population4.1. The Early-Type Stars
The four central, early-type stars BD+65 ◦ ◦ α ◦ ◦ ◦ ◦ . ′ ◦ ◦ ∼ ⊙ ) Class 0 source FIRS 2, is still embed-ded within its natal envelope south of the clustercore and will likely emerge as a mid-B type star(Fuente et al. 2014). In summary, there are atleast four other B-type stars that are associatedwith NGC 7129 and the molecular cloud complex. α Emission Sources
In his landmark study of Be and Ae stars as-sociated with nebulosity, Herbig (1960) reportedthat both BD+65 ◦ α
234 exhibit H α emission, but also noted the presence of several9aint stars having H α emission near the limit ofthe slitless grating exposures within the nebulos-ity of NGC 7129. From R/Hα magnitude ratios,Hartigan & Lada (1985) found that in additionto LkH α
234 and BD+65 ◦ α imag-ing including GGD 32, 34 and 35, HH 103 and HH105. Hartigan & Lada (1985) suggested that LkH α
234 is the driving source for at least some of theseHH objects. Magakian et al. (2004) identified 22emission-line sources in NGC 7129, 16 of whichwere previously unknown. G. H. Herbig providedMagakian et al. (2004) with a list of H α emissionsources identified on an earlier WFGS image (notavailable for this analysis). Of 13 sources identifiedby Herbig as exhibiting H α emission, five were notfound in emission by Magakian et al. (2004), whiletheir source MMN 11 was not identified by Her-big as an emitter. The WFGS images examinedhere reveal what appears to be a flat continuumfor MMN 11 (i.e. no absorption or emission), con-sistent with Herbig’s findings. Of the 22 emission-line stars, Magakian et al. (2004) found that abouthalf were concentrated in the central region of thereflection nebula. Ten of their sources were con-fidently identified as CTTS and another seven asweak-line T Tauri stars (WTTS).The H α slitless grism survey presented hereidentified over 50 H α emission sources in a regionsome 150 square arcminutes in area, which is out-lined in Figure 2. The HYDRA low-dispersionspectroscopy revealed ∼
30 additional emitters,most of which lie outside the boundaries of theWFGS survey, have measured equivalent widthsbelow the detection threshold of the WFGS ( ∼ α emissionsources identified here are shown in Figure 2.In Table 1 ordered by right ascension, wepresent identifiers for the detected H α emis-sion sources, J2000 coordinates, spectral types, V − band magnitudes, V − R C and V − I C colors; J − H and H − K S colors, and K S magnitudes from2MASS; [3.6], [4.5], [5.8], and [8.0] Spitzer
IRACphotometry from Stelzer & Scholz (2009) and ref-erences therein as well as Wide-Field Infrared Sur-vey Explorer (WISE) w , w , w
3, and w α numberis assigned, continuing the numbering conventioninitiated by Herbig (1998) in IC 348 and subse-quently continued by Herbig & Dahm (2002) inIC 5146, Herbig et al. (2004) in NGC 1579, Dahm& Simon (2005) in NGC 2264, Dahm (2005) inNGC 2362, Herbig & Dahm (2006) in L988, andDahm et al. (2012) in IC 1274. The measuredequivalent widths of the H α emission profiles, W ( Hα ), and of Ca II λ W ( Hα ) or W (8542) for underlying absorption structure.The equivalent width of H α is a well-establishedindicator of accretion processes and chromosphericactivity in pre-main sequence stars (for a review,see Bertout 1989). Traditionally the boundaryseparating classical and WTTS was placed atW(H α )=10˚A (e.g. Herbig 1998). While no physi-cal interpretation was intended for this value, cleardifferences in the processes responsible for emis-sion have since been recognized for CTTS, i.e. ac-cretion, and WTTS, i.e. enhanced chromosphericactivity. Various spectral type dependent criteriahave been suggested to better distinguish accretorsfrom non-accretors, e.g. Mart´ın (1998) and White& Basri (2003). In Figure 13 we plot W ( Hα ) as afunction of V − I C color (top panel) and W ( Hα )as a function of K S − [4 .
5] color (bottom panel).If
Spitzer [4.5] photometry were not available fora given source, K S − w W ( Hα ) and V − I C color, a log-linear relationshipis evident when comparing W ( Hα ) and K S − [4 . K − w α emission sources are active late-K andM-type field dwarfs (dMe) that exhibit enhancedchromospheric activity. H α emission strengthsamong dMe stars, however, are typically weak,W(H α ) <
10 ˚A (Hodgkin et al. 1995; Reid et al.10995; Hawley et al. 1996), and would predom-inantly affect the statistics of the WTTS popu-lation. Other potential sources of contaminationinclude chromospherically active giants, RS CVnbinaries, cataclysmic variables, and active galax-ies. The field density of such objects is expectedto be low, particularly within the molecular cloudswhere extinctions reach A V ∼ α emission sources is low, but cer-tainly non-zero. Chandra
ACIS X-ray Detected Sources
Stelzer & Scholz (2009) obtained a 22 ks long in-tegration of NGC 7129 using ACIS onboard
Chan-dra , detecting 59 X-ray sources. The majority(47/59) of these sources have 2MASS near-infraredcounterparts, but prior to this survey few had op-tical photometry available. Correlating these X-ray detections with 2MASS and
Spitzer infraredexcess sources, Stelzer & Scholz (2009) identifiedone Class 0/I source, 16 Class II sources, and30 Class III candidates, leaving 12 unclassified.Contamination of the X-ray selected sample fromfield interlopers, particularly among the Class IIIsources was considered, however, using X-ray lu-minosities of field dwarfs, Stelzer & Scholz (2009)estimate that < − X-ray emitting field stars liewithin the central core of the cluster. A contribu-tion of extragalactic X-ray sources was also consid-ered, but reduced sensitivity at large off-axis an-gles should limit the total number of extragalacticsources considerably.The X-ray detections from the
Chandra
ACISintegration are plotted as green crosses in Figure2. Over half, ∼
30, of the X-ray detections havecounterparts in the H α emission selected sample.About a half-dozen X-ray detections in the haloof the star forming region lacking optical counter-parts are possible extragalactic sources. Othersappear to be associated with stars that were notidentified as H α emitters, but that could be clus-ter members. Clearly X-ray and H α emission aretracing similar activity in these pre-main sequencecandidates. There are a substantial number of H α emission sources, however, that were not detectedby the X-ray survey, particularly off-axis. Thisis likely the result of the reduced sensitivity and the relatively shallow ACIS exposure. Included inTable 1, ordered by right ascension, are 46 of 59 X-ray sources identified by Stelzer & Scholz (2009),their J2000 coordinates, spectral types, optical ( V , V − R C , V − I C ) and infrared photometry from2MASS ( J − H , H − K S , K S ), Spitzer , and WISE.Of the remaining 13 sources, eight were outside ofthe fields of view of the optical photometric sur-veys and five had no optical counterparts.
Chandra or the H α Emission Survey
The
Spitzer
IRAC and MIPS photometry ofGutermuth et al. (2004) and Muzerolle et al.(2004) were used by Stelzer & Scholz (2009) toidentify sources with infrared excess emission at-tributable to circumstellar disks. Stelzer & Scholz(2009) made their source selection using the [3 . − [4 . , [5 . − [8 .
0] and the K S − [4 . J − H color-color diagrams, resulting in the identification of64 Class II sources and 13 Class 0/I candidatecluster members. Of these 77 sources, 46 werewithin the Chandra field of view, but were not de-tected in X-rays. Eliminating 15 of these sourcesthat were detected with H α emission and that al-ready appear in Table 1, we list in Table 2 theremaining 31 pre-main sequence candidates thatwere selected on the basis of their infrared photom-etry. Contamination of these pre-main sequencecandidates is dominated by extragalactic sources,predominantly star forming galaxies. Such ob-jects, however, reside in a specific region of the[3 . − [4 . , [5 . − [8 .
0] color-color diagram andcan be distinguished from pre-main sequence starsby establishing a brightness cutoff determined bystatistical means (Gutermuth et al. 2008; Stelzer& Scholz 2009). In Table 2 we present optical( I C , R C − I C ) photometry for these Spitzer excesssources and infrared photometry from 2MASS,
Spitzer , and WISE. These sources are shown inFigure 2 as open red squares and appear to bepreferentially positioned within the semi-circulararc of remnant molecular gas to north, east andsouth of the cluster core. The Class I source adja-cent to LkH α
234 is 2MASS J21430696+660641.7,which is discussed in more detail in § .5. Spectroscopically Classified SourcesLacking H α or X-ray Emission In Table 3 we present optical and infrared pho-tometry from 2MASS and WISE for sources thatwere classified by the low-dispersion spectroscopicsurvey, but that lack H α or detected X-ray emis-sion. In §
5. Cluster Properties5.1. Reddening and Extinction
Extinction and CO column density are in gen-eral strongly correlated, implying that dust is well-mixed with the molecular gas in molecular cloudcomplexes. Shown in Figure 14 is a map of vi-sual extinction ( A V ) derived from CO integratedline intensity obtained at the Five College RadioAstronomical Observatory (FCRAO) in 1993 byLAH. The map is superimposed upon a near in-frared mosaic of the region with extinction peaksthat are coincident with the compressed ridge tothe north, east and south of the cluster core, peak-ing near A V ∼
20 mag. The evacuated cavity isclearly evident with extinction dropping sharply tothe west and gradually to the east across the sur-face of the molecular cloud. Also shown in Figure14 is a map of integrated CS line intensity. The CSextinction map demonstrates significant enhance-ments near the molecular outflow originating byLkH α
234 and to the south near FIRS 2.The low-dispersion spectroscopy allowed spec-tral classification for ∼
130 stars in the cluster re-gion. Combined with the optical photometry, thespectral types permitted an independent determi-nation of extinction across the region. To estimateextinction for sources of known spectral type, weassume the standard ratio of total-to-selective ab-sorption, i.e. R = A V /E ( B − V ) = 3 .
08 (He etal. 1995) to derive a normal reddening law givenby A V = 2 . E ( V − I C ). Intrinsic colors of 5–30 Myr old pre-main sequence stars taken fromPecaut & Mamajek (2013) were used to determine V − I C color excesses and extinctions. The averageextinction suffered by 50 probable cluster mem- bers taken from the H α and X-ray selected stellarsamples is A V =1.8 mag. An abnormal extinctionlaw induced by dust grains having sizes substan-tially larger than interstellar grains or the peculiarspectral energy distributions for these pre-main se-quence members could impact this adopted meanextinction value. Shown in Figure 15 is the observed V − I C , V color-magnitude diagram for all sources detectedby the KPNO T2KA CCD imaging survey. Thecandidate members of NGC 7129, i.e. the H α emission and X-ray detected sources, are super-posed in the figure. The zero age main sequence(ZAMS) of Siess et al. (2000) is overplotted us-ing the dwarf colors presented by Kenyon & Hart-mann (1995) and assuming a distance of 1150 pc(Straiˇzys et al. 2014). The cluster sequence is well-defined by the activity-selected sample and lies atleast two magnitudes above the ZAMS, even forthe early-type members.The X-ray and H α emission populations over-lap considerably and appear to have identifiedthe majority of possible cluster stars in the color-magnitude diagram. A collection of faint ( V > α emission sources are evident outside ofthe nominal cluster sequence lying on or just be-low the ZAMS. Most of these sources lie on theperiphery of the molecular clouds, three to thewest where extinction is minimal. If taken at facevalue, the isochronal ages assigned to these sourceswould be much greater than that of the cluster it-self. Such objects are generally interpreted as hav-ing edge-on disk geometries that dramatically re-duce stellar luminosity, or as background contam-inants. The roughly 10% fraction of sources lyingsubstantially below the cluster pre-main sequenceand potentially having edge-on disk geometries isconsistent with having a random distribution ofdisk orientations.In Figure 16 we show the extinction-corrected( V − I C ) , V color-magnitude diagram for the H α emission stars and X-ray sources. Stars of knownspectral type have been corrected individually forreddening using the intrinsic colors of 5–30 Myrpre-main sequence stars from Pecaut & Mamajek(2013). All other sources have been dereddenedusing the mean extinction value derived for the12 α and X-ray samples. The age of the cluster emerging from NGC 7129is undoubtedly young given the presence of oneand possibly two Herbig Be stars (LkH α ◦ §
6, the evolutionarytimescale of the photodissociation region envelop-ing BD+65 ◦ < yr.Cluster ages are generally inferred by fitting theirstellar populations in color-magnitude diagramswith pre-main sequence isochrones.The grid of Siess et al. (2000) models was usedto estimate the ages and masses for the opticallydetected H α emitters and X-ray sources havingestablished spectral types. Uncertainties involvedin the use of pre-main-sequence models fall intotwo broad categories; the physics used in model-ing stellar evolution from the birthline to the zero-age main sequence, and the transformation be-tween theoretical and observational planes. Mod-els of pre-main sequence evolution treat convec-tion, opacity, radiative transfer, rotation, and ac-cretion uniquely, leading to variations in predictedevolutionary paths for a given stellar mass. Initialconditions establishing the birthline are also notwell understood. For an in depth discussion of is-sues related to the ages of young stars, the readeris referred to Soderblom et al. (2014).Transforming between theoretical and obser-vational planes is typically achieved by fittingmain-sequence colors and bolometric correctionsas a function of effective temperature, a problem-atic assumption given the lower surface gravities,cooler temperatures, enhanced chromospheric ac-tivity and accretion processes generally associatedwith pre-main-sequence stars. The Siess et al.(2000) models adopt the dwarf colors of Kenyon& Hartmann (1995), which themselves are derivedfrom Bessell & Brett (1988).With these caveats stated, the median age forthe 50 cluster members having established spec-tral types determined from the models of Siesset al. (2000) is ∼ V − I C > ∼
35 Myr; however some ofthe more advanced ages are potentially attributedto neutral extinction induced by edge-on disk ge-ometries. These ages are sensitive to the assumeddistance of the cluster, intrinsic variability, errorsin extinction, as well as unresolved binaries. Theextreme case of having companions of equal masswould elevate stars in the color-magnitude dia-gram by 0.75 mag, resulting in the assignment ofyounger ages.Recently, revisions to age estimates of youngclusters and associations have advanced publishedages by a factor of two or more. Pecaut et al.(2012) fit isochrones to the F and G-type stars inthe color-magnitude diagram of the Upper Scor-pius OB association, suggesting a revision to itsage from ∼ < ∼ ∼ ∼ ∼ ∼
12 Myr, respectively. Appli-cation of such techniques to the population ofNGC 7129 would similarly advance its age fromthe estimate derived here if these techniques andassumptions are robust to further tests.The inferred masses of the cluster membersrange from ∼ ⊙ to 5.6 M ⊙ (the most mas-sive being BD+65 ◦ ∼
21 within the central cluster region im-plies that the survey is complete to about ∼ ⊙ . The Keck LRIS R C and I C − band imag-ing is the deepest of the three photometric sur-13eys presented here, extending to I C ∼
22 withinthe core of NGC 7129 where extinction is signif-icantly reduced. Shown in Figure 17 is the ob-served R C − I C , I C color-magnitude diagram forthe Keck LRIS photometry, uncorrected for red-dening. The Siess et al. (2000) models do notextend below 0.1 M ⊙ , but it is clear from the fig-ure that about two dozen sources are present thatwould lie along the 2 Myr isochrone if extrapo-lated to lower masses. The evolutionary models ofBaraffe et al. (1998) extend to much lower masses,well below the substellar mass limit and into theplanetary mass regime. Assuming a mean extinc-tion of A V ∼ A I ∼ M I = 8 .
53 or I C =19.83 mag in Figure 17. Here there are ahandful of sources in the photometric cluster se-quence that are possible very low mass stars orbrown dwarf candidates, but a deeper photomet-ric survey as well as spectroscopy, particularly inthe near-infrared, are needed for confirmation. NGC 7129 was observed from 3.6 to 24 µ mwith Spitzer using IRAC and MIPS as part ofthe
Spitzer
Young Stellar Cluster Survey (AOR:3655168 and 3663616). These observations arepresented by Megeath et al. (2004) as well asGutermuth et al. (2004, 2009). Stelzer & Scholz(2009) adopted the photometry of Gutermuth etal. (2004, 2009) to derive a disk fraction for the
Chandra
X-ray and infrared-selected sources of ∼ ± A V < ∼ +24 − %. Although considered the least-biased sub-sample, it is also the least complete interms of the number of included cluster members.Here we combine 2MASS, Spitzer
IRAC, andWISE photometry for the activity-selected sourcesin NGC 7129 to examine infrared excesses for can-didate cluster members. Shown in Figure 18 arethe H − K S , J − H (left panel) and the K S − [4 . J − H (right panel) color-color diagrams for theH α emission sources, X-ray sources, infrared ex-cess sources not identified with X-ray or H α emis-sion, and the spectroscopically classified sourceslacking either H α or X-ray emission. If IRAC [4.5] channel photometry were not available, WISE w H − K S , J − H color-color digram distinguishesthe most prominent infrared excess sources thatlie to the right of the reddening boundary for nor-mal dwarfs. These excesses arise from hot > K S − [4 . J − H color-color diagram is much more effective at isolatingdisk-bearing sources given that the IRAC [4.5] andWISE w K S − [4 . J − H color-color diagramto represent the demarcating limit for disk-bearingsources, we find the disk fraction for the activity-selected sample having [4.5] or w ± ± ∼ ± ±
6% (Lada et al. 2006) and Chamaeleon I,50 ±
6% (Luhman et al. 2008), but substantiallylarger than the disk fractions of the more evolvedUpper Scorpius OB association, 19% (Carpenteret al. 2006) and NGC 2362, 19% (Dahm & Hillen-brand 2007).Figure 18 suggests that H α emission is a betterdiscriminant for identifying disk-bearing sourcesthan X-ray emission. Longer exposure times withACIS onboard Chandra would certainly have iden-tified additional cluster members, but the effec-tiveness of simple ground-based, slitless grism ormulti-object spectroscopic techniques at isolatingactive stars cannot be ignored. It should also benoted that a handful of spectroscopically classifiedsources lacking either H α or X-ray emission appearto have substantial infrared excess and are there-14ore candidate cluster members. These sources areidentified as having infrared excess in the com-ments column of Table 3. The majority of theclassified sources lacking activity indicators, how-ever, appear to cluster along the upper extinctionboundary for normal dwarfs where reddened gi-ants might be expected to lie, supporting theirnon-membership status in NGC 7129. In sum-mary, to conduct a population census of youngstar forming regions, H α emission, X-ray emissionand infrared excess are needed to ensure complete-ness.
6. Discussion6.1. Star Formation in NGC 7129 and the105 . ◦ . ◦ Star formation is at an advanced stage withinNGC 7129 with the recently formed massive starsBD+65 ◦ ◦ ◦ ◦ ◦ ′ ) 21 cm H I survey of NGC 7129revealed a ∼ ′ diameter ring of emission appar-ently associated with the surface of the molecularcloud. H on the cloud surface has likely beendissociated by interstellar ultraviolet radiation,producing the observed ring. Within this ring,Matthews et al. (2003) note a bright knot of H I emission centered on BD+65 ◦ I knot and BD+65 ◦ ∼ − between the CO andthe H I emission. Matthews et al. (2003) postu-late that BD+65 ◦ yrs on the cloud periphery. This would also im-ply that BD+65 ◦ ◦ ◦ ◦ α emission is apparentin the former, presumably formed by recombina-tion within the surrounding gaseous disk. Stellarwinds are responsible for the blue-shifted forbid-den emission present in the spectrum. In contrast,the spectrum of BD+65 ◦ ◦ ∼ µ m. The star falls on the locus of themain sequence in the near infrared K S − [4 . J − H color-color diagram shown in Figure 18.BD+65 ◦ ◦ ◦ A V =1.7 and 2.1 mag, respectively.The preponderance of spectroscopic evidencesuggests that BD+65 ◦ I emission is un-resolved, but may represent an expanding shellof dissociated molecular gas driven by the UVflux from BD+65 ◦ ◦ emission some170 ′′ long or 0.95 pc, was noted by Schultz et al.(1997) in their narrow-band, near-infrared imag-ing survey of NGC 7129. This PDR appears tooutline the molecular ridge and is thought to beilluminated by UV emission from BD+65 ◦ α
234 and 2MASS J21430696+660641.7are located. Maps of CO column density (e.g.15echis et al. 1978; Miskolczi et al. 2001; Figure14a), reveal another dense core ∼ ◦ ∼ ⊙ . Whether triggered by com-pression from the formation of BD+65 ◦ ◦ α emission sources or embeddedClass 0 and I sources are found in this region, pos-sibly implying that star formation is in its earliestphase here.The activity-selected sample of candidate mem-bers is nearly evenly divided between those con-centrated within the cluster core, defined as lyingwithin 2 ′ ( ∼ ◦ α emission sources, X-ray sources and embedded protostars have beenidentified, suggesting that star formation is wellunderway in this region of the molecular cloud.These isolated sources have likely formed indepen-dently of the central young cluster.To the west, several H α emitters are locatedaround the molecular cloud core GGD 32, with HH103 marking the terminus of star formation activ-ity. No embedded protostars are found here andthe detected H α sources are predominantly knotsof HH objects. The paucity of activity-selectedsources further west suggests that few have driftedfar from their formation sites, arguing for recentand rapid star formation in L1181. α LkH α
234 lies at the apex of the one-parsecscale, central cavity, the boundaries of which aredemarcated on optical and infrared continuum im-ages by bright arcs of nebulous emission and anincreased density in stars, both cluster membersand background sources. Northeast of NGC 7129,bright 4.5 µ m emission is evident in the Spitzer
IRAC 4-color image of the region presented by Gutermuth et al. (2004). This shocked CO emis-sion is possibly produced by the impact of super-sonic jets originating near LkH α α
234 isalso a radio continuum source (Bertout & Thum1982; Snell & Bally 1986) and was thought topower an optical jet (Ray et al. 1990). The calcu-lated mass loss rate for the optical outflow is ∼ × − M ⊙ yr − and implies a momentum fluxwhich is two orders of magnitude less than thatof the molecular outflow. The optical jet pointsalong the symmetry axis of the molecular cavity,with a number of faint stars aligned along the sameaxis. Because of its high collimation, however, thejet is unlikely to have formed the parsec-scale cav-ity. Ray et al. (1990) report that the HH objectspresent throughout the region are not associatedwith LkH α
234 itself based upon a proper motionanalysis. Shocked H emission was reported byWilking et al. (1990), Schultz (1989), and Schultzet al. (1997) south of LkH α α J, H , and K ′ . Shown in Figure 19 is a median com-bined, ∼ ′′ × ′′ K ′ image of the region havingan effective integration time of 100 s. The arc ofnebulosity evident in the NIRC2 image representsthe apex of the ∼ ′′ long rim of H emission dis-cussed by Schultz et al. (1997). LkH α
234 appearsto be involved with this nebulosity, blowing backthe gas and dust to form an illuminated wedge-shaped rim. The AO imaging reveals at least adozen sources including a well-resolved companionof LkH α
234 having a position angle (PA) of 97 ◦ and a separation of 1 . ′′
88. This source was notedpreviously by Perrin (2006) in near-infrared polari-metric observations of the region. About ∼ . ′′ α
234 lies the embedded Class I pro-tostar 2MASS J21430696+660641.7, which onlybecomes prominent in the NIRC2 imaging at K ′ .The NIRC2 imaging also reveals two pointsources along the southern arm of the nebulousarc, including a resolved visual binary with a sep-aration of ∼ . ′′
33 and ∆ m Kp ∼ . ′′ α ◦ . Weintraub et al.(1994) reported an embedded companion lying 3 ′′ α
234 (PA 290-340 ◦ ), their po-larization source PS 1, and suggested that thissource is responsible for driving the bipolar molec-ular outflow associated with the region. PS 1and their source IRS 5 (PA=330 ◦ , 2 . ′′ α ◦ /240 ◦ , which corresponds with a sub-stantial number of HH objects identified in thearea (McGroarty et al. 2004).Perrin (2006) describes two mid-infrared sources ∼ ′′ northwest of LkH α Spitzer
IRAC [5.8] post basiccalibrated data (BCD) image of the region, cen-tered near LkH α α ∼ ′′ northwest of LkH α α
234 and 2MASS J21430696+660641lies a third bright infrared point source in theIRAC [5.8] image that lacks counterpart in theNIRC2 K ′ image. This source is readily appar-ent in Spitzer
IRAC [8.0] imaging and is likelyanother embedded Class 0 or I protostar. Assum-ing all NIRC2 and IRAC sources in this regionto be cluster members, the stellar surface densityin the immediate vicinity of LkH α
234 is severalhundred ( > − . Given the numberof embedded sources emerging here, this regionat the apex of the parsec-scale cavity must beextremely young. There are no other comparableexamples of clustered, luminous protostars evidentin the region.
7. Summary
We have obtained deep, optical (
V, R C , I C )photometry for ∼ α emission sources have beenidentified in the region, the majority of whichare presumably members of a T Tauri star pop-ulation emerging from the associated molecularcloud. Combined with 59 X-ray sources detectedin a shallow, 22 ks Chandra
ACIS observation byStelzer & Scholz (2009), the H α emission sourcesform a relatively narrow pre-main sequence in the V − I C , V color-magnitude diagram. Inspection ofthe color-magnitude diagram for all sources sug-gests that these two stellar activity indicators haveidentified the majority of the optically-detectablepre-main sequence population, down to a limitingmagnitude of V ∼ A V ∼ ∼ α and X-rayselected sources having established spectral types,although a substantial age dispersion is present( ∼ ⁀ Spitzer and WISE, we estimate the diskfraction of the activity- selected sample of clus-ter members to be ∼ ± α or X-ray emission that exhibit infrared excess arepresent. We find a strong log-linear relationshipbetween W ( Hα ) and K S − [4 .
5] color, as might beexpected from these two inner disk indicators.Merging the activity-selected sample of 94sources with 31 infrared selected pre-main se-quence candidates from Stelzer & Scholz (2009)not detected with X-ray or H α emission, and eightinfrared excess sources from the spectroscopicallyclassified sample of stars lacking X-ray or H α emis-sion, the cluster population of NGC 7129 has beenincreased from ∼
90 members to more than 130.High dispersion optical spectroscopy of BD+65 ◦ ◦ ◦ ◦ α
234 is suggestiveof active accretion with numerous metallic and for-bidden transitions in emission as well as H α andH β . HIRES spectra obtained in 1999 and 2004show significantly different H α emission profilesincluding the presence of a deep absorption fea-ture in the P Cygni-like structure in the earlierspectrum. The high dispersion spectrum of SVS13 reveals weak emission reversal in the core ofH α as well as Fe I λλ λ α
234 usingNIRC2 on Keck II reveals a number of embeddedsources in the region including the Class I proto-star 2MASS J21430696+660641.7. A bright, well-resolved companion of LkH α
234 is also detectedhaving a PA of 97 ◦ and a separation of 1 . ′′
88. Ofnote several mid-infrared sources that are appar-ent in
Spitzer
IRAC and MIPS imaging of the re-gion are not detected in the Keck AO K ′ imaging.Assuming all NIRC2 and IRAC sources to be asso-ciated with the cluster, the stellar surface densitynear LkH α
234 is several hundred stars pc − .Our interpretation of the structure of the rem-nant molecular clouds and the distribution ofyoung stars in the region is that BD+65 ◦ α
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This 2-column preprint was prepared with the AAS L A TEXmacros v5.2.
V R C I C − band three-color image ofNGC 7129 and the L1181 molecular cloud ob-tained by G. H. Herbig in 1999 October (orien-tation: north up, east left). This 7 . ′ × . ′ ◦ ◦ α
234 (east) andSVS 13 (north). LkH α
234 lies within the denseridge of molecular gas that extends several ar-cminutes and outlines the evacuated region of themolecular cloud. To the northeast, just over halfthe distance from the cluster center to the corner,is the ghostly outline of HH 105, and to the south-west, near the edge of the field of view, HH 103which is likely associated with FIRS 2 or V392 Cep(RNO 138). FIRS 2, undetected at optical wave-lengths, lies near the center of the bottom edge ofthe field of view, just south of V392 Cep. 21ig. 2.— A 20 ′ × ′ field of the red DSS imageof NGC 7129. The 150 square arcminute area sur-veyed with the WFGS and the region imaged withLRIS are outlined. The KPNO T2KA imagingdata encompasses the entire field of view. Filledred circles mark the positions of H α emissionsources, green crosses represent X-ray detectedsources from the Chandra
ACIS observation, andopen red squares show the positions of Class 0/I/IIsources that were not detected in X-rays by Stelzer& Scholz (2009) or by the H α emission survey pre-sented in this work. 22ig. 3.— (left panel) The observed V − I C , V color-magnitude diagram for all ∼ ′ × ′ region. (right panel) The R C − I C , R C color-magnitude diagram for all sources detectedin the Keck LRIS 8 ′ × ′ imaging survey of the coreof NGC 7129. No corrections for interstellar red-dening have been applied to the photometry. 23ig. 4.— Comparison of the KPNO photometryfrom 1993 June with that from the UH 2.2 m from1999 October. The slight offset present in the V − I C colors arises from extended red transmission inthe UH 2.2 m I C filter. 24ig. 5.— Comparison of the KPNO photometryfrom 1993 June with that from the Keck LRISimaging survey of 1999 June. Photometric cali-bration of the LRIS data was achieved by apply-ing airmass and zero point corrections only, i.e. nocolor terms were applied, which likely explains thecolor offset. 25ig. 6.— Examples of low-dispersion spectra oflate-type cluster members obtained using HYDRAon WIYN. The sources are ordered by spectraltype, classified using the temperature sensitiveindices measuring the TiO bandhead absorptionstrengths at λ λ ◦ α (left) andH β (right). Strong H α emission ( W = −
25 ˚A) isapparent with wings extending beyond ±
550 kms − . There is no indication of an underlying pho-tospheric absorption profile. The emission line isdouble-peaked, and the radial velocities of the redand blue peaks are annotated in the figure. H β re-veals a similar double-peaked emission structure,but is substantially weaker ( W = − ◦ α (left) andH β (right). The spectrum reveals weak evidencefor possible emission reversal within the core ofthe H α absorption feature with a radial veloc-ity of ∼− − , consistent with that ofthe molecular cloud. Otherwise the spectrum ofBD+65 ◦ ◦ α α
234 obtained in 1999 December and 2004 June cen-tered near H α showing substantial differences instructure between the two epochs. The 1999 spec-trum reveals a deep absorption feature in the PCygni-like profile that is not evident in the laterspectrum. A second narrow absorption core is ev-ident near line center, just blueward of the sharpemission peak. The emission peak and the steppedredward slopes are remarkably similar in both ob-servations. 29ig. 10.— Sections of orders from the 2004 HIRESspectrum of LkH α
234 centered near H β (leftpanel), Fe II λ I D lines (right panel). Radial velocities of variousfeatures in the spectra are annotated for reference. 30ig. 11.— Sections of orders from the 2010 HIRESspectrum of SVS 13 centered near H α (left panel)and H β (right panel). The heliocentric radial ve-locity of the emission core centered within thebroad H α absorption profile is annotated. SVS13 is possibly a Herbig Be star, but shows sub-stantially less emission than either LkH α
234 orthe classical Be star BD+65 ◦ I D lines (left panel), the numerous metallicemission lines near λ α (right panel). Radialvelocities of various features are indicated in thepanels for reference. 32ig. 13.— (top panel) V − I C color plotted againstW(H α ) for the H α emission sources listed in Ta-ble 1. For reference the colors of 5–30 Myr starsare plotted along the abscissa. No obvious corre-lation is present, but the colors shown here havenot been corrected for extinction. (bottom panel) K S − [4 .
5] color plotted as a function of W(H α )for the H α emission sources identified here. Thereddest color expected from an unreddened stel-lar photosphere of M5 spectral type is indicatedby the broken vertical line. A log-linear relation-ship is apparent between these two accretion diskparameters. 33ig. 14.— ( a ) A map of visual extinction ( A V ) de-rived from CO integrated line intensity obtainedat the Five College Radio Astronomical Observa-tory (FCRAO) in 1993 by LAH. The contour mapis overlaid upon a near infrared mosaic image ofNGC 7129 obtained on the KPNO 50-inch tele-scope using the SQIID camera. Extinction con-tours are plotted with intervals of 5 mag over therange from 2.5 to 60 mag. ( b ) A map of integratedCS line intensity from data obtained at FCRAOsuperposed upon the same near infrared mosaicimage of NGC 7129. Extinction contours are plot-ted with intervals of A V ∼ V − I C , V color-magnitude diagram of NGC 7129 with the H α emission sources shown as solid red circles, X-raysources as green crosses, and other sources fromthe KPNO T2KA survey as gray points. Thezero age main sequence (ZAMS) of Siess et al.(2000) is overplotted assuming the dwarf colorspresented by Kenyon & Hartmann (1995), derivedfrom those of Bessell & Brett (1988) and a distanceof 1150 pc (Straiˇzys et al. 2014). 35ig. 16.— The extinction-corrected ( V − I C ) , V color-magnitude diagram for the H α emissionstars and X-ray sources with available optical pho-tometry. Stars of known spectral type have beencorrected individually for reddening using the in-trinsic colors of 5–30 Myr pre-main sequence starsfrom Pecaut & Mamajek (2013). Sources with-out spectral type information are plotted using themean extinction derived for the cluster A V = 1 . ⊙ evo-lutionary tracks of the solar metallicity models ofSiess et al. (2000), assuming a distance of 1150 pc(Straiˇzys et al. 2014). 36ig. 17.— The observed R C − I C , I C color-magnitude diagram of NGC 7129 constructed fromthe Keck LRIS photometry, uncorrected for red-dening. Photometric errors are shown for allsources. The Siess et al. (2000) isochrones for2 Myr, the approximate cluster age, and 100 Myrand the evolutionary track for a 0.1 M ⊙ star areoverplotted. The shaded region represents thearea where very low mass cluster members are ex-pected to lie, including brown dwarf candidates.The Baraffe et al. (1998) models predict thatthe sub-stellar mass limit lies near I C =19.83 mag,where a handful of sources are evident in the clus-ter sequence. Deeper photometric surveys as wellas spectroscopy are needed for confirmation. 37ig. 18.— The H − K S , J − H (left panel) andthe K S − [4 . J − H (right panel) color-colordiagrams for the H α emission sources (red cir-cles), X-ray sources (green crosses), infrared ex-cess sources lacking X-ray emission or H α emis-sion (red squares) and spectroscopically classifiedstars lacking either H α emission or X-ray emission(gray circles). The main sequence colors of Pecaut& Mamajek (2013) are overplotted in both pan-els as dashed lines and the approximate redden-ing boundaries for dwarfs are shown with slopesderived using extinction data for diffuse interstel-lar clouds from Martin & Whittet (1990). As-suming the extinction boundary for dwarfs in the K S − [4 . J − H color-color diagram to repre-sent the demarcation line for disk-bearing sources,we find the disk fraction for all activity-selectedsources (i.e. X-ray, H α emission) included here tobe ∼ ± ∼ ′′ × ′′ K ′ image centered near LkH α
234 obtained usingNIRC2 and the Keck II NGS AO system. Thearc of nebulosity evident in the NIRC2 image rep-resents the apex of the ∼ ′′ long rim of H emission discussed by Schultz et al. (1997). Awell-resolved companion of LkH α
234 having aPA of 97 ◦ and a separation of 1 . ′′
88 is evidentas is the embedded young Class I source 2MASSJ21430696+660641.7, some 12 . ′′ Spitzer
IRAC [5.8] post BCD imagecentered near LkH α α
234 and2MASS J21430696+660641.7 are saturated in theimage, resulting in black cores for these sources.Three luminous infrared sources are evident thatwere not detected in the NIRC2 imaging of theregion. It is possible that one of these sources isresponsible for the molecular outflow and for thebow-shocked emission enveloping SVS 13 to thewest. 40 able 1Optical and Infrared Photometry for H α and X-ray Emission Sources in NGC 7129 Identifiera α δ
SpT V b V − RC b V − IC b J − H c H − KS c KS c [3.6]d [4.5]d [5.8]d [8.0]d w w w w
4e W(H α f ) W(8542g ) Other Identifiers Notesh(J2000) (J2000) (˚A) (˚A)MMN 1 21 42 23.08 +66 06 04.4 M3V 20.47 1.56 3.11 1.01 0.66 13.39 12.51 12.14 11.78 11.02 12.39 12.02 ... ... 32.9 0.3 S3-U840IH α
763 21 42 26.60 +66 06 17.0 K5 19.60 1.29 2.31 0.76 0.34 14.59 ... ... ... ... 14.00 14.08 ... ... 8.3 ...IH α
764 21 42 29.57 +66 05 20.9 G8-K2 19.72 0.96 1.80 0.50 0.82 15.25 ... ... ... ... ... ... ... ... 7.5 ...IH α
765 21 42 32.40 +66 04 59.1 G5-K0 18.57 0.86 1.63 0.56 0.08 15.01 ... ... ... ... 14.52 15.12 ... ... 11.5 ecrIH α
766 21 42 34.72 +66 05 18.6 M3V 17.80 1.17 2.54 0.64 0.15 13.13 12.87 12.80 12.82 13.06 13.22 13.15 ... ... 4.3 ecr S3-X4MMN 2 21 42 38.80 +66 06 35.8 ... 20.68 2.22 3.60 1.32 0.97 12.51 11.01 10.59 10.42 10.19 10.96 10.49 ... ... 437 ... S3-U939, HH 242 wk contS3-X41 21 42 38.91 +66 07 08.7 ... 18.37 1.67 3.20 1.09 0.44 11.08 ... ... ... ... 10.42 10.33 ... ... ... ...IH α
767 21 42 40.23 +66 13 28.7 ... ... ... ... 0.94 0.58 12.51 ... ... ... ... 11.74 11.05 8.92 6.70 206 ... wk contS3-X52 21 42 40.34 +66 10 07.2 A1 12.44 0.33 0.73 0.30 0.13 10.58 10.52 10.52 10.27 9.73 10.43 10.37 ... ... ... ... SVS 2IH α
768 21 42 40.49 +66 09 51.6 ... 19.95 0.85 1.58 ... ... 14.87 13.12 12.33 11.54 10.48 13.13 11.92 ... ... 86.0 ... S3-U1612MMN 3 21 42 41.92 +66 09 24.5 ... 21.19 1.82 3.78 0.84 0.35 13.99 13.56 13.29 13.08 12.30 13.66 13.23 ... ... 22: ... S3-U1522 wk contIH α
769 21 42 44.22 +66 10 07.0 M4.5V 21.28 1.82 3.82 0.83 0.24 14.30 ... ... ... ... 13.80 13.29 ... ... 8.4 0.8S3-X40 21 42 45.32 +66 07 04.4 ... 20.91 1.63 3.42 1.02 0.59 13.39 13.13 13.05 12.35 ... 11.39 10.90 ... ... ... ...IH α
770 21 42 45.51 +66 06 30.6 G0: 19.65 1.18 2.26 0.83 0.31 14.41 ... ... ... ... ... ... ... ... 5.0 absIH α
771 21 42 46.08 +66 05 56.2 M2V 18.17 1.31 2.60 0.77 0.27 12.75 12.58 12.60 12.57 13.15 12.56 12.38 ... ... 5.3 abs S3-X31BD+65 ◦ α
772 21 42 46.12 +66 13 45.8 ... ... ... ... 0.72 0.41 13.55 ... ... ... ... 13.29 12.92 10.88 ... 50.1 ...IH α
773 21 42 46.17 +66 06 56.6 M0V 19.65 1.45 2.86 0.77 0.27 12.75 ... ... ... ... 12.56 12.38 ... ... 9.5 0.2IH α
774 21 42 46.55 +66 06 33.4 K3 19.42 1.24 2.16 0.70 0.56 14.35 ... ... ... ... ... ... ... ... 4.2 absIH α
775 21 42 46.59 +66 06 22.3 M5V 21.63 1.30 3.33 0.74 0.40 14.98 ... ... ... ... ... ... ... ... 8: flatIH α
776 21 42 46.87 +66 06 57.4 M0 19.65 1.45 2.86 1.02 0.51 12.09 11.24 10.91 10.55 9.74 ... ... ... ... 25.9 abs S3-X39IH α
777 21 42 47.05 +66 04 57.8 ... 15.54 1.02 2.00 0.77 0.28 11.05 10.79 10.74 10.54 10.00 10.67 10.37 ... ... 2.5 ... S3-X2IH α
778 21 42 47.46 +66 07 03.4 M2V 21.66 1.72 3.84 1.02 0.52 13.47 ... ... ... ... ... ... ... ... 20.8 0.7IH α
779 21 42 47.90 +66 06 53.0 ... 17.91 1.28 2.53 1.04 0.33 12.09 11.69 11.71 10.89 ... ... ... ... ... 4.4 ... S3-X23IH α
780 21 42 48.13 +66 07 43.2 K5: 21.42 1.76 3.22 1.01 0.37 14.31 ... ... ... ... ... ... ... ... 4.9 absIH α
781 21 42 49.87 +66 05 42.6 ... 20.02 1.36 3.29 0.64 0.29 13.72 13.53 13.39 ... ... ... ... ... ... 4: ... S3-X8 em?IH α
782 21 42 49.93 +66 05 54.6 M4 21.61 2.10 4.08 0.74 0.45 14.09 ... ... ... ... ... ... ... ... 18.3 absBD+65 ◦ α
783 21 42 50.92 +66 06 03.6 M2V 17.73 1.21 2.38 0.85 0.24 12.55 12.42 12.37 12.24 ... ... ... ... ... 5.3 abs S3-X11IH α
784 21 42 50.99 +66 03 59.2 ... 19.96 1.01 1.88 ... ... ... ... ... ... ... 15.22 14.07 ... ... 8: ... wk contMMN 5 21 42 51.42 +66 05 56.2 ... 21.82 1.56 3.03 1.07 0.56 13.57 12.62 12.09 11.52 10.53 ... ... ... ... 280 ... S3-U815 wk contS3-X35 21 42 51.96 +66 06 33.4 ... 18.06 0.99 2.39 0.73 0.18 13.13 12.63 12.68 ... ... ... ... ... ... ... ...IH α
785 21 42 52.30 +66 05 35.3 M1V 18.98 1.30 2.70 0.86 0.32 13.19 ... ... ... ... ... ... ... ... 3.7 absMMN 6 21 42 52.61 +66 06 57.2 M1V 18.95 1.48 2.94 1.17 0.85 11.80 10.81 10.24 9.77 9.15 ... ... ... ... 69.2 2.5 S3-X25MMN 7 21 42 53.14 +66 07 14.8 ... 20.58 1.12 1.94 1.42 1.23 12.93 11.61 10.93 10.41 9.57 ... ... ... ... 201 24.6 S3-U1085 wk contIH α
786 21 42 53.21 +66 07 20.8 ... 19.30 1.42 2.71 1.15 0.51 12.68 11.62 11.29 10.82 9.92 ... ... ... ... 4.2 ... S3-U1109MMN 8 21 42 53.45 +66 09 19.6 ... 21.87 1.71 2.77 1.49 0.92 14.58 12.91 12.36 11.87 11.23 13.25 12.47 ... ... 234 ... S3-U1504 wk contMMN 9 21 42 53.49 +66 08 05.3 M2V 17.55 1.26 2.50 0.85 0.24 12.12 11.85 11.78 11.22 ... 11.22 11.16 ... ... 2.6 abs S3-X29S3-X45 21 42 54.08 +66 08 14.9 G8 19.80 1.57 2.98 1.17 0.43 12.82 12.52 12.55 12.55 12.29 ... ... ... ... ... ...IH α
787 21 42 54.71 +66 06 35.6 M0V 19.00 1.43 2.59 1.00 0.62 12.56 11.66 11.37 11.02 10.05 ... ... ... ... 5.4 abs S3-X36MMN 10 21 42 54.80 +66 06 12.7 ... 19.01 1.38 2.59 0.94 0.35 12.91 12.58 ... ... ... ... ... ... ... em? ... S3-X32 wk contIH α
788 21 42 54.87 +66 06 31.4 M1V 19.42 1.53 2.90 1.05 0.27 13.42 ... ... ... ... ... ... ... ... 4.9 absIH α
789 21 42 54.89 +66 07 21.3 M3V 20.00 1.71 3.40 1.05 0.35 12.84 12.50 12.44 11.96 ... ... ... ... ... 5.8 abs S3-X26S3-X37 21 42 55.72 +66 06 45.0 ... 21.16 1.61 3.64 1.00 0.31 14.27 13.62 13.37 ... ... ... ... ... ... ... ...IH α
790 21 42 55.76 +66 05 42.9 M3.5V 20.41 0.74 2.81 0.85 0.40 13.97 13.43 13.38 ... ... ... ... ... ... 5.7 ecr S3-X48IH α
791 21 42 55.86 +66 07 21.1 M1V 20.70 1.69 3.28 1.31 0.82 12.47 11.16 10.54 9.98 9.02 ... ... ... ... 28.1 8.6 S3-U1107MMN 11 21 42 56.25 +66 06 02.1 ... 15.75 0.95 1.85 0.77 0.25 11.41 11.28 11.13 10.78 ... ... ... ... ... em? ... S3-X10S3-X18 21 42 56.77 +66 06 37.2 ... 17.93 1.31 2.57 0.98 0.48 12.21 11.47 11.21 10.44 ... ... ... ... ... ... ...IH α
792 21 42 57.15 +66 06 34.9 K5 17.18 1.11 2.11 0.92 0.22 12.53 ... 12.00 ... ... ... ... ... ... 1.6 abs S3-X15IH α
793 21 42 57.40 +66 07 15.1 M3V 19.72 1.69 3.38 0.81 0.36 12.98 ... ... ... ... ... ... ... ... 3.2 absMMN 12 21 42 58.10 +66 07 39.3 M5V 20.49 1.94 3.93 0.77 0.50 13.03 ... ... ... ... ... ... ... ... 13.6 flatIH α
794 21 42 58.18 +66 05 40.5 M2V 18.64 1.09 2.27 0.80 0.13 13.20 ... ... ... ... ... ... ... ... 8.9 4.8 S3-X47S3-X43 21 42 58.34 +66 07 26.3 ... 22.68 2.53 4.93 1.69 0.71 11.91 11.44 11.39 10.93 ... ... ... ... ... ... ...IH α
795 21 42 58.36 +66 05 27.3 M2.5V 18.88 1.30 2.75 0.93 0.39 12.64 11.79 11.39 ... ... ... ... ... ... 18.6 0.5 S3-X6BD+65 ◦ α
796 21 42 59.41 +66 11 12.3 ... ... ... ... 0.76 0.53 14.77 ... ... ... ... ... ... ... ... 50: ... wk contHBC 731 21 42 59.61 +66 04 33.8 M1.5V 18.69 1.58 3.08 1.26 0.68 10.95 10.18 9.73 9.39 8.91 10.20 9.59 7.58 5.60 54.9 4.5 S3-X1IH α
798 21 42 59.97 +66 01 01.0 ... ... ... ... 0.84 0.20 13.67 ... ... ... ... 13.60 13.47 ... ... em? ...IH α
799 21 42 59.98 +66 06 42.4 M3V 19.69 1.47 3.26 0.86 0.34 13.15 12.73 13.05 ... ... ... ... ... ... 7.0 ecr S3-X19HBC 732 21 43 00.00 +66 11 27.9 M2 16.35 1.01 2.11 1.02 0.68 11.01 ... ... ... ... 10.06 9.13 6.58 4.10 27.7 ... MMN 13, V350 CepMMN 14 21 43 00.23 +66 06 47.4 M0V 20.02 1.53 2.73 1.38 0.69 12.09 ... ... ... ... 9.53 9.33 ... ... 92.7 9.3SVS 13 21 43 01.71 +66 07 08.9 B5 14.57 0.86 1.78 0.68 0.31 10.25 9.19 8.81 ... ... 7.64 7.14 ... ... em ecr S3-X51IH α
800 21 43 01.88 +66 06 44.7 K3-5V 17.24 1.18 2.22 0.89 0.40 12.02 11.12 10.80 11.15 ... ... ... ... ... 3.8 abs S3-X20 able 1— Continued
Identifiera α δ
SpT V b V − RC b V − IC b J − H c H − KS c KS c [3.6]d [4.5]d [5.8]d [8.0]d w w w w
4e W(H α f ) W(8542g ) Other Identifiers Notesh(J2000) (J2000) (˚A) (˚A)MMN 15 21 43 02.46 +66 07 03.9 ... 19.64 1.34 2.55 0.90 0.85 12.26 ... ... ... ... ... ... ... ... 9: ...S3-X50 21 43 03.01 +66 06 55.9 ... ... ... ... ... ... ... 12.79 12.59 ... ... ... ... ... ... ... ...IH α
801 21 43 03.20 +66 11 15.0 ... ... ... ... 1.16 1.12 14.34 ... ... ... ... 11.70 9.90 6.01 3.33 111 ... GGD 33AIH α
802 21 43 03.43 +66 05 26.4 M2 17.86 1.24 2.49 0.98 0.53 12.01 ... ... ... ... ... ... ... ... 59.3 4.5IH α
803 21 43 04.71 +66 00 30.5 ... ... ... ... 1.16 0.62 13.51 ... ... ... ... 12.93 12.31 10.68 ... 28: ... wk contIH α
804 21 43 04.95 +66 06 53.6 K2V 17.90 1.42 2.58 1.08 0.72 11.26 ... ... ... ... ... ... ... ... 6.3 abs S3-X22IH α
805 21 43 05.09 +66 09 29.5 M7 22.45 1.93 4.05 0.64 0.26 14.90 14.23 14.07 13.70 13.11 14.62 14.33 ... ... 14.9 abs S3-U1542LkH α
234 21 43 06.82 +66 06 54.2 B8 12.48 0.66 1.34 1.33 1.12 7.08 5.79 5.15 4.45 3.33 4.69 2.90 1.32 -1.75 56.6 9.3 MMN 16IH α
806 21 43 11.41 +66 12 55.5 ... ... ... ... 1.02 0.60 12.70 ... ... ... ... 11.89 11.26 9.43 7.32 166 ...MMN 17 21 43 11.61 +66 09 11.4 M1V 16.30 1.08 2.16 0.80 0.31 11.49 11.04 10.73 10.38 9.70 11.16 10.79 8.82 7.03 4.8 abs S3-X30IH α
807 21 43 12.26 +66 06 05.8 M5V 21.65 1.48 3.80 0.74 0.40 13.95 13.36 13.05 12.48 ... ... ... ... ... 7.0 flat S3-U849IH α
808 21 43 12.35 +66 09 55.4 M4.5 19.71 1.52 3.08 0.91 0.31 13.59 13.00 12.74 12.39 11.85 13.15 12.73 11.18 ... 17.4 ecr S2-U1640IH α
809 21 43 14.36 +66 08 59.2 M4V 22.48 1.62 4.21 0.73 0.37 14.93 14.23 13.89 13.59 12.98 ... ... ... ... 36.9 abs S3-U1433IH α
810 21 43 14.43 +66 07 34.8 M3 20.50 1.41 2.95 1.18 0.49 13.84 ... ... ... ... 12.89 10.98 ... ... 2.9 flatIH α
811 21 43 15.28 +66 07 57.1 M2.5V 21.31 1.66 3.38 1.67 0.75 12.59 11.57 11.03 10.41 9.41 ... ... ... ... 6.2 flat S3-X28MMN 19 21 43 16.83 +66 05 48.6 M2V 18.31 1.29 2.48 0.88 0.18 13.12 12.74 12.57 12.45 11.99 ... ... ... ... 15.8 abs S3-X9IH α
812 21 43 18.06 +66 05 35.2 M3V 19.74 1.47 3.06 0.77 0.29 13.70 13.39 13.27 13.29 13.12 ... ... ... ... 3.6 flat S3-X7IH α
813 21 43 19.37 +66 07 21.5 M4.5V 20.70 1.67 3.50 0.77 0.40 13.89 13.90 13.72 13.62 13.43 ... ... ... ... 17.5 0.8 S3-X42IH α
814 21 43 21.07 +66 06 22.8 ... 17.83 1.23 2.56 0.66 0.15 12.75 12.44 ... 12.32 12.42 ... ... ... ... 2: abs S3-X14 binaryS2-X2 21 43 24.89 +66 07 34.1 ... 23.25 1.44 3.00 ... ... ... 17.12 16.15 ... ... ... ... ... ... ... ...IH α
815 21 43 26.95 +66 09 36.5 M0V 16.49 0.87 1.67 0.71 0.18 12.72 12.67 12.66 12.60 12.55 12.73 12.74 ... ... 1.6 ecr S2-X4IH α
816 21 43 28.10 +66 00 57.2 ... ... ... ... 0.95 0.33 12.55 ... ... ... ... 12.25 11.91 10.77 ... 15.0 ...S3-X56 21 43 29.28 +66 03 31.5 G6 11.17 0.31 0.58 0.29 0.04 9.69 9.69 9.69 9.64 9.64 9.64 9.65 10.13 9.41 ... ... SVS 16MMN 20 21 43 31.82 +66 08 50.6 ... 18.21 1.20 2.34 1.04 0.60 12.30 11.59 11.29 11.02 10.31 11.88 11.47 ... ... 21.1 ... S2-X1IH α
817 21 43 36.87 +66 07 52.6 K5: 19.33 1.16 2.19 0.70 0.45 14.40 ... ... ... ... 14.23 14.19 ... ... 4.4 absMMN 22 21 43 43.44 +66 07 30.8 ... 18.57 1.38 2.70 1.05 0.46 12.15 11.43 11.05 10.63 10.06 11.65 11.16 9.60 ... em? ... S2-X5IH α
818 21 43 43.71 +66 08 22.3 M3 19.61 1.45 2.95 0.90 0.25 13.66 ... ... ... ... ... ... ... ... 7.3 flatIH α
819 21 44 05.37 +66 05 53.1 K5 18.70 1.09 2.15 1.54 0.93 11.22 9.83 9.33 8.92 8.16 10.09 9.38 7.32 4.94 60.6 5.3 S2-U820IH α
820 21 44 06.34 +66 04 23.1 ... 18.71 1.36 2.62 1.13 0.69 11.38 ... ... ... ... 10.51 10.00 7.96 5.68 2.7 ...IH α
821 21 44 07.82 +66 04 33.2 M3.5 19.57 1.59 3.16 0.94 0.31 13.21 ... ... ... ... 12.70 12.26 ... ... 25.4 ecr.aIH α number unless previously identified by Magakian et al. (2004), Herbig (1957), or the Herbig Bell Catalog (HBC).bOptical photometry from the UH 2.2 m or the KPNO 0.9 m.cNear-infrared photometry from the 2MASS Point Source Catalog.d Spitzer
IRAC photometry from Stelzer & Scholz (2009).eWISE photometry from the AllWISE Source Catalog.fPositive values indicate emission.gPositive values indicate emission; abs - Ca II λ λ able 2Photometry for Infrared Sources without X-ray or H α Emission a Source α δ RC − IC b IC b J − H c H − KS c KS c [3.6]d [4.5]d [5.8]d [8.0]d w w w w
4e Other Identifiers(J2000) (J2000)S3-U1178 21 41 55.30 +66 07 41.5 ... ... ... ... ... 15.86 14.90 13.98 12.78 16.10 15.12 12.15 8.99S3-U1367 21 42 17.67 +66 08 40.3 ... ... 1.15 0.39 14.63 13.68 13.23 12.91 12.40 14.06 13.61 ... ...S3-U1194 21 42 42.42 +66 07 45.2 2.42 18.62 1.35 0.78 13.45 12.56 12.21 12.23 11.68 12.07 11.80 ... ...S3-U1521 21 42 42.86 +66 09 24.0 ... ... ... ... ... 16.23 15.25 13.84 12.79 ... ... ... ...S3-U1246 21 42 48.23 +66 08 00.6 2.30 18.16 1.40 0.81 13.08 11.69 11.14 10.62 9.67 11.23 10.71 ... ...S3-U722 21 42 54.63 +66 05 20.3 2.66 18.50 0.95 0.69 13.87 12.51 12.64 ... ... ... ... ... ...S3-U546 21 42 57.75 +66 04 23.5 1.08 18.00 ... 0.82 13.66 11.80 10.94 9.95 8.54 11.85 10.74 7.10 5.07 V392 Cep, RNO 138S3-U1780 21 42 59.47 +66 10 35.8 ... ... ... 1.07 14.61 13.54 13.00 12.52 12.05 13.88 13.09 ... ...S3-U270 21 42 59.82 +66 01 54.9 ... ... ... ... ... 16.83 16.59 15.91 14.33 ... ... ... ...S3-U419 21 43 01.78 +66 03 24.4 ... ... ... ... ... 13.02 10.41 10.17 9.08 13.17 9.86 6.03 0.36 FIRS 2S3-U500 21 43 02.01 +66 04 02.7 ... ... ... ... ... 13.64 12.98 12.18 11.29 13.37 12.32 ... ...S3-U1611 21 43 02.62 +66 09 50.7 2.60 18.08 0.92 0.59 14.20 13.54 13.16 12.65 11.93 13.92 13.32 ... ...S3-U1294 21 43 02.89 +66 08 14.2 ... ... 0.92 0.41 15.01 14.15 13.83 13.58 13.43 ... ... ... ...S3-U822 21 43 04.38 +66 05 56.4 ... 18.55 0.58 0.65 14.47 ... 12.55 ... ... ... ... ... ...S3-U1242 21 43 05.92 +66 07 58.5 ... ... ... ... ... 13.78 12.70 12.10 11.65 ... ... ... ...S3-U968 21 43 06.96 +66 06 41.7 ... ... ... 2.34 10.89 7.54 6.59 5.67 5.06 8.38 6.75 4.15 0.70 J21430696+660641.7S3-U1103 21 43 07.84 +66 07 18.5 2.42 19.38 1.87 0.91 13.94 13.04 12.57 11.76 10.88 ... ... ... ...S3-U550 21 43 11.17 +66 04 25.6 ... ... ... ... ... 13.91 13.42 12.98 12.33 13.83 13.11 ... ...S3-U1026 21 43 12.42 +66 06 55.9 ... ... ... ... ... 14.16 13.73 13.25 12.23 ... ... ... ...S3-U1211 21 43 14.17 +66 07 46.5 ... ... ... ... 14.34 10.55 9.34 8.41 7.51 ... ... ... ...S3-U1169 21 43 14.83 +66 07 37.5 ... ... ... ... 14.77 12.93 10.72 10.44 10.22 ... ... ... ...S3-U1350 21 43 24.13 +66 08 31.5 ... ... ... 1.43 14.19 12.86 11.28 10.05 8.96 13.07 11.04 8.85 4.64 GGD 34CS3-U1059 21 43 24.90 +66 07 04.7 1.58 19.72 ... ... ... 14.23 13.33 12.59 11.56 ... ... ... ...S2-U1313 21 43 26.64 +66 08 20.5 ... ... ... ... ... 14.66 14.19 13.79 13.24 14.97 13.92 ... ...S3-U821 21 43 29.32 +66 05 55.7 2.70 18.46 0.92 0.57 14.39 13.47 13.04 12.52 11.02 13.71 13.07 ... ...S2-U1083 21 43 29.92 +66 07 09.2 ... 21.79 ... ... ... 14.67 14.24 13.99 13.38 ... ... ... ...S2-U804 21 43 33.12 +66 05 49.0 ... ... ... ... ... 16.69 15.83 14.92 13.37 ... ... ... ...S2-U2219 21 43 38.59 +66 12 30.6 ... ... ... ... ... 13.58 13.34 12.80 11.99 13.42 13.06 ... ...S2-U1660 21 43 47.04 +66 10 01.2 1.11 17.04 0.70 0.51 14.19 14.05 14.03 13.72 13.00 13.84 13.82 ... ...S2-U613 21 43 48.70 +66 04 46.2 ... ... 1.23 0.57 13.08 12.40 12.15 11.83 10.87 12.33 11.88 9.65 ...S2-U1713 21 43 49.35 +66 10 12.9 1.24 17.79 0.79 0.21 14.86 14.53 14.47 14.29 13.36 14.33 14.53 ... ...aYoung Stellar Objects identified by Stelzer & Scholz (2009) based upon infrared excess emission.bOptical photometry from Keck LRIS imaging, UH 2.2 m or the KPNO 0.9 m.cNear-infrared photometry from the 2MASS Point Source Catalog.d
Spitzer mid-infrared photometry from Stelzer & Scholz (2009).eMid-infrared photometry from the AllWISE Source Catalog. able 3Photometry for Spectroscopically Classified Stars without X-ray or H α Emission
Sourcea α δ
SpT V b V − RC b RC − IC b J − H c H − KS c KS c w w w w
4d Comments(J2000) (J2000)1 21 42 22.75 +66 07 52.9 G3-5 16.65 0.82 0.75 0.54 0.22 13.25 13.06 13.14 ... ...2 21 42 22.85 +66 06 56.3 G-K1 20.57 1.34 1.11 0.80 0.55 14.90 ... 14.06 ... ... IR excess3 21 42 23.07 +66 06 42.5 K1-3 18.86 1.04 0.87 0.66 0.13 14.59 ... ... ... ...4 21 42 23.31 +66 08 47.4 M0 17.45 1.01 0.93 0.68 0.21 13.45 13.35 13.35 ... ...5 21 42 24.74 +66 06 21.4 F9-G5 17.59 1.23 1.14 0.88 0.32 12.22 11.72 11.88 ... ...6 21 42 25.19 +66 10 09.0 F7-G5 18.14 0.96 0.91 0.42 0.32 14.15 13.99 13.92 ... ...7 21 42 26.84 +66 07 42.5 G9-K0 10.59 0.57 0.50 0.55 0.07 7.96 7.84 7.93 7.68 ... SVS 48 21 42 28.35 +66 04 08.7 F5-9 18.41 0.99 0.95 0.62 0.22 14.18 13.43 13.66 ... ... IR excess9 21 42 31.22 +66 08 04.8 G9-K1 19.17 1.01 0.91 0.52 0.29 14.98 14.55 ... ... ...10 21 42 31.86 +66 07 08.7 G6-8 17.29 0.99 0.95 0.61 0.18 13.11 12.53 12.71 ... ...11 21 42 32.57 +66 10 24.9 G8-K0 18.54 1.02 0.96 0.69 0.16 14.26 14.07 14.23 ... ...12 21 42 33.75 +66 08 02.3 M2.5 19.93 1.69 1.55 0.93 0.40 13.37 12.98 13.03 ... ...13 21 42 34.28 +66 03 12.6 G-K4 18.37 1.20 0.92 0.79 0.23 13.73 13.42 13.59 ... ...14 21 42 35.03 +66 04 09.6 G5-K0 18.36 0.82 0.77 0.52 0.23 14.90 14.10 14.99 ... ...15 21 42 35.69 +66 05 49.3 K3 17.44 1.05 0.95 0.74 0.32 12.80 12.77 13.02 ... ...16 21 42 38.58 +66 09 41.4 M2.5 20.27 1.35 1.32 0.50 0.70 15.10 14.39 14.26 ... ... IR excess17 21 42 39.05 +66 07 09.9 K5 18.37 1.67 1.53 1.09 0.44 11.08 10.46 10.39 ... ... IR excess18 21 42 41.26 +66 03 33.7 G2-5 16.02 0.77 0.74 0.52 0.12 12.80 12.66 12.73 12.27 ...19 21 42 44.96 +66 07 48.0 G2-K 22.03 2.06 1.57 1.03 0.48 14.06 ... ... ... ...20 21 42 45.98 +66 08 15.6 K5 20.49 1.68 1.49 1.03 0.52 13.44 12.57 12.49 ... ... IR excess21 21 42 46.02 +66 10 20.3 K5: 22.69 2.18 2.21 1.11 0.65 13.34 12.79 12.39 ... ... IR excess22 21 42 47.73 +66 05 35.2 G2-5 17.86 0.97 0.86 0.64 0.08 13.86 12.84 12.54 ... ... IR excess23 21 42 50.66 +66 03 31.3 G9-K2 16.95 0.73 0.58 0.61 0.17 13.99 13.88 ... ... ...24 21 42 50.47 +66 08 32.7 K2-5 21.26 1.53 1.37 1.32 0.31 14.74 ... ... ... ...25 21 42 51.16 +66 05 45.3 F2 17.29 0.59 0.58 0.26 -0.03 14.90 ... ... ... ...26 21 42 51.94 +66 09 44.9 M1 18.05 1.03 0.91 0.70 0.23 13.93 13.97 ... ... ...27 21 42 53.97 +66 08 15.1 G5-K0 19.80 1.57 1.41 1.17 0.43 12.82 ... ... ... ...28 21 42 55.18 +66 06 25.4 K5 15.83 0.84 0.68 0.68 0.15 12.53 ... ... ... ...29 21 42 58.04 +66 05 54.7 G3-5 14.21 0.41 0.40 0.31 0.20 12.26 ... ... ... ...30 21 43 00.20 +66 05 46.1 G8 17.47 0.76 0.65 0.84 0.01 13.87 ... ... ... ...31 21 43 05.32 +66 04 52.0 M1 19.57 1.09 1.11 0.74 0.30 14.93 ... ... ... ...32 21 43 05.05 +66 10 12.4 M1 20.97 1.37 1.51 1.02 0.48 14.14 14.07 14.03 ... ...33 21 43 05.53 +66 03 28.7 K5 16.93 0.86 0.66 0.72 0.07 13.63 13.41 13.45 ... ...34 21 43 07.51 +66 09 01.5 M3 20.84 1.85 1.72 1.12 0.36 13.20 ... ... ... ...35 21 43 09.85 +66 05 48.8 M3 22.52 2.46 1.93 1.02 0.47 13.86 ... ... ... ...36 21 43 13.04 +66 05 50.8 M4.5 20.49 1.62 1.84 0.80 0.39 13.64 ... ... ... ...37 21 43 14.63 +66 10 13.6 K1 18.46 1.20 1.13 0.78 0.29 13.31 13.16 13.10 ... ...38 21 43 14.93 +66 09 07.1 M0 17.99 1.05 0.92 0.66 0.26 13.86 13.73 13.80 ... ...39 21 43 17.55 +66 04 18.5 G0-2 20.29 1.51 1.42 0.89 0.47 13.58 ... ... ... ...40 21 43 20.84 +66 03 37.1 M1 17.55 1.04 1.01 0.68 0.19 13.45 13.22 13.19 ... ...41 21 43 21.66 +66 02 46.1 G3 14.25 0.44 0.42 0.40 0.03 12.40 12.32 12.34 ... ...42 21 43 31.12 +66 07 43.7 M2 19.38 1.18 1.18 0.61 -0.04 14.90 ... 14.44 ... ...43 21 43 31.18 +66 07 24.4 G8-K1 14.53 0.62 0.52 0.52 0.12 11.96 11.86 11.93 ... ...44 21 43 31.18 +66 09 54.7 G6-8 15.70 1.33 1.24 0.93 0.32 9.96 9.74 9.72 9.85 ... SVS 1445 21 43 32.68 +66 10 11.8 G-K1 20.16 1.49 1.38 1.19 0.25 13.55 13.15 13.15 ... ...46 21 43 40.01 +66 03 31.9 G4 12.92 0.38 0.34 0.33 0.04 11.13 11.06 11.09 11.20 ...47 21 43 40.64 +66 05 16.5 M5 21.50 1.38 1.80 0.56 0.76 15.08 15.14 15.05 ... ...48 21 43 44.89 +66 07 0.12 A2 15.29 0.90 0.90 0.49 0.21 11.40 11.17 11.13 ... ...49 21 43 45.10 +66 04 38.1 G8 15.57 0.56 0.46 0.37 0.15 13.28 13.18 13.21 ... ...50 21 43 45.37 +66 08 22.9 M1 17.50 1.09 1.10 0.58 0.28 13.22 12.83 12.62 ... ... IR excess51 21 43 47.03 +66 10 01.7 G5-K0 19.37 1.22 1.11 0.70 0.51 14.19 13.84 13.82 ... ...52 21 43 47.40 +66 08 49.5 M3 20.01 1.16 1.26 0.81 0.48 15.05 ... ... ... ...53 21 43 50.02 +66 07 52.3 M3.5 16.84 1.22 1.46 0.60 0.23 11.94 11.68 11.53 ... ...54 21 43 50.48 +66 09 38.8 K2 18.72 1.29 1.22 0.90 0.30 13.11 12.69 12.74 ... ...55 21 43 51.63 +66 03 39.0 K0-3 19.95 1.20 1.12 0.92 0.19 14.70 14.66 14.71 ... ...56 21 43 54.23 +66 06 42.5 K5: 21.18 1.66 1.37 1.14 0.23 14.37 13.91 13.91 ... ...57 21 43 54.30 +66 09 10.4 K5: 20.25 1.36 1.20 0.96 0.45 14.48 14.12 14.32 ... ...58 21 43 55.69 +66 05 29.6 K5: 19.63 1.46 1.33 0.98 0.37 13.29 12.99 12.97 ... ...59 21 43 55.58 +66 08 16.9 F7-G5 18.54 1.11 1.03 0.72 0.19 13.96 13.66 13.69 ... ...60 21 43 55.98 +66 03 05.3 G6 15.68 0.62 0.53 0.56 0.10 13.11 13.04 13.08 ... ...61 21 43 58.34 +66 07 11.7 K5 21.26 1.72 1.29 0.91 0.45 14.73 14.55 14.56 ... ...62 21 43 59.96 +66 04 37.0 K4 16.90 0.83 0.65 0.65 -0.03 13.83 13.59 13.67 ... ...63 21 44 00.52 +66 05 17.3 M0 16.82 1.00 0.95 0.74 0.14 12.85 12.64 12.63 ... ...64 21 44 00.95 +66 07 24.7 K1 18.20 1.40 1.26 0.97 0.33 12.31 12.08 12.11 ... ... able 3— Continued
Sourcea α δ
SpT V b V − RC b RC − IC b J − H c H − KS c KS c w w w w
4d Comments(J2000) (J2000)65 21 44 02.99 +66 04 56.2 G-K 19.20 1.39 1.23 0.89 0.31 13.46 13.20 13.19 ... ...66 21 44 04.32 +66 06 41.6 K2 16.74 1.31 1.20 0.90 0.27 11.23 11.02 11.04 ... ...67 21 44 05.12 +66 06 00.2 F7 17.04 1.03 0.96 0.61 0.21 12.78 12.63 12.58 ... ...68 21 44 05.41 +66 04 52.6 M2 18.65 1.11 1.09 0.55 0.16 14.50 14.20 14.15 ... ...69 21 44 06.59 +66 09 13.1 G7-K0 17.02 1.14 1.05 0.82 0.20 12.23 12.04 12.05 ... ...70 21 44 06.71 +66 08 10.0 G5 17.84 0.96 0.90 0.56 0.19 14.01 13.87 13.85 ... ...71 21 44 08.14 +66 06 04.2 G7-K0 18.51 1.13 1.02 0.80 0.11 13.88 13.44 13.38 ... ... IR excess?72 21 44 08.64 +66 03 15.9 G5-8 19.47 1.30 1.18 0.86 0.42 13.91 13.70 13.70 ... ...aIdentifierbOptical photometry from the KPNO 0.9 m or the UH 2.2 m.cNear-infrared photometry from the 2MASS Point Source Catalog.dMid-infrared photometry from the AllWISE Source Catalog.4d Comments(J2000) (J2000)65 21 44 02.99 +66 04 56.2 G-K 19.20 1.39 1.23 0.89 0.31 13.46 13.20 13.19 ... ...66 21 44 04.32 +66 06 41.6 K2 16.74 1.31 1.20 0.90 0.27 11.23 11.02 11.04 ... ...67 21 44 05.12 +66 06 00.2 F7 17.04 1.03 0.96 0.61 0.21 12.78 12.63 12.58 ... ...68 21 44 05.41 +66 04 52.6 M2 18.65 1.11 1.09 0.55 0.16 14.50 14.20 14.15 ... ...69 21 44 06.59 +66 09 13.1 G7-K0 17.02 1.14 1.05 0.82 0.20 12.23 12.04 12.05 ... ...70 21 44 06.71 +66 08 10.0 G5 17.84 0.96 0.90 0.56 0.19 14.01 13.87 13.85 ... ...71 21 44 08.14 +66 06 04.2 G7-K0 18.51 1.13 1.02 0.80 0.11 13.88 13.44 13.38 ... ... IR excess?72 21 44 08.64 +66 03 15.9 G5-8 19.47 1.30 1.18 0.86 0.42 13.91 13.70 13.70 ... ...aIdentifierbOptical photometry from the KPNO 0.9 m or the UH 2.2 m.cNear-infrared photometry from the 2MASS Point Source Catalog.dMid-infrared photometry from the AllWISE Source Catalog.