Emission-Line Galaxies from the HST PEARS Grism Survey I: The South Fields
A.N. Straughn, N. Pirzkal, G.R. Meurer, S.H. Cohen, R.A. Windhorst, S. Malhotra, J. Rhoads, J.P. Gardner, N.P. Hathi, R.A. Jansen, N. Grogin, N. Panagia, S.D.S. Alighieri, C. Gronwall, J. Walsh, A. Pasquali, C. Xu
aa r X i v : . [ a s t r o - ph . C O ] J u l Draft version November 13, 2018
Preprint typeset using L A TEX style emulateapj v. 08/22/09
EMISSION–LINE GALAXIES FROM THE HST PROBING EVOLUTION AND REIONIZATIONSPECTROSCOPICALLY (PEARS) GRISM SURVEY I: THE SOUTH FIELDS
Amber N. Straughn , Norbert Pirzkal , Gerhardt R. Meurer , Seth H. Cohen , Rogier A. Windhorst ,Sangeeta Malhotra , James Rhoads , Jonathan P. Gardner , Nimish P. Hathi , Rolf A. Jansen , NormanGrogin , Nino Panagia , Sperello di Serego Alighieri , Caryl Gronwall , Jeremy Walsh , Anna Pasquali ,Chun Xu Draft version November 13, 2018
ABSTRACTWe present results of a search for emission–line galaxies in the Southern Fields of the Hubble SpaceTelescope PEARS (Probing Evolution And Reionization Spectroscopically) grism survey. The PEARSSouth Fields consist of five ACS pointings (including the Hubble Ultra Deep Field) with the G800Lgrism for a total of 120 orbits, revealing thousands of faint object spectra in the GOODS-South regionof the sky. Emission–line galaxies (ELGs) are one subset of objects that are prevalent among thegrism spectra. Using a 2-dimensional detection and extraction procedure, we find 320 emission linesorginating from 226 galaxy “knots” within 192 individual galaxies. Line identification results in 118new grism–spectroscopic redshifts for galaxies in the GOODS-South Field. We measure emissionline fluxes using standard Gaussian fitting techniques. At the resolution of the grism data, the H β and [O iii ] doublet are blended. However, by fitting two Gaussian components to the H β and [O iii ]features, we find that many of the PEARS ELGs have high [O iii ]/H β ratios compared to other galaxysamples of comparable luminosities. The star–formation rates (SFRs) of the ELGs are presented, aswell as a sample of distinct giant star–forming regions at z ∼ Subject headings: catalogs — techniques: spectroscopic — galaxies: starburst INTRODUCTION
The Probing Evolution And Reionization Spectroscop-ically (PEARS ) ACS grism survey provides a 200HST orbit dataset from which one can investigate manydifferent aspects of galaxy evolution. High-redshift ob-jects such as Ly α galaxies, Lyman break galaxies, andAGN are being investigated by Rhoads et al. (2009) andGrogin et al. (2009, in preparation). Elliptical galax-ies (Ferreras et al. 2009, in preparation), and emission–line galaxies (ELGs; Straughn et al. 2008) are also be-ing studied. A similar deep grism program was car-ried out in the GRAPES project (Pirzkal et al. 2004, Xuet al. 2007). Here we discuss results of a search for ELGs [email protected] Astrophysics Science Division, Observational Cosmology Lab-oratory, Goddard Space Flight Center, Code 665, Greenbelt, MD20771 Space Telescope Science Institute, Baltimore, MD 21218 Department of Physics and Astronomy, Johns Hopkins Univer-sity, Baltimore, MD 21218 School of Earth and Space Exploration, Arizona State Univer-sity, Tempe, AZ 85287 Department of Physics & Astronomy, University of California,Riverside, CA 92521 INAF - Osservatorio Astrofisico di Arcetri, I-50125 Firenze,Italy Department of Astronomy & Astrophysics, Pennsylvania StateUniversity, University Park, PA, 16802, USA ESO Space Telescope European Co-ordinating Facility, D-85748 Garching bei Mnchen, Germany Max–Planck–Institut for Astronomie, Koenigstuhl 17, D-69117 Heidelberg, Germany Shanghai Institute of Technical Physics, 200083 Shanghai,China http://archive.stsci.edu/prepds/pears in the PEARS South Fields. In particular, we presentnew grism spectroscopic redshifts for 118 galaxies in theGOODS South Field, as well as discuss the ELG lineluminosities, star–formation rates, and AGN candidatesamong the sample.For many years, galaxies that are actively forming starshave been regarded as important objects to study in thecontext of galaxy assembly. In particular, the H α , [O iii ],and [O ii ] lines have been used extensively to determinetheir SFRs (Kennicutt 1983; Gallego et al. 1995; Gal-lego et al. 2002; Brinchmann et al. 2004; Westra & Jones2007; Kewley et al. 2004; Glazebrook et al. 2004). Manyprojects have specifically used slitless spectroscopy in or-der to study ELGs. Ground-based slitless spectroscopyhas been used by Kurk et al. (2004) to identify ELGs.Yan et al. (1999) derived the H α luminosity function andSFR for galaxies at z & α , also using the NICMOSdata. The GRism ACS Program for Extragalactic Sci-ence (GRAPES; Pirzkal et al. 2004, Malhotra et al. 2005)has also yielded slitless spectroscopy for galaxies in theHubble Ultra Deep Field (HUDF), including a large sam-ple of ELGs (Pirzkal et al. 2006, Xu et al. 2007). PEARSis a follow-up grism survey to GRAPES, and provides alarger spectroscopic dataset of ELGs in an 8 × larger area.In Straughn et al. (2008) we investigated in detail several Straughn et al.methods aimed at detecting these ELGs in the PEARSHUDF pointing. In the current paper we use the mostefficient method and extend that study to include theremaining four PEARS South ACS Fields. In Section2 we discuss the PEARS dataset used here. Section 3outlines the methods used to detect the ELGs. In Sec-tion 4 we present results of the search, including a tableof the South Field ELGs detected along with new spec-troscopic redshifts, and a discussion of line luminosities,star-formation rates, AGN candidates, and the radial dis-tribution of galaxy knots. In Section 5 we summarize ourfindings and discuss future prospects. DATA
The HST PEARS grism survey consists of nine ACSFields observed with the G800L grism. The G800L grismyields low-resolution ( R ∼ λ =6000-9500˚A. Five fields were observed in theGOODS South region (including the Hubble Ultra DeepField) and four in GOODS North. Here we present prop-erties of ELGs detected in the PEARS South fields. ThePEARS HUDF was observed for 40 orbits (four roll an-gles, obtaining spectra for sources with limiting contin-uum AB magnitude i ′ AB . . i ′ AB . . METHODS
We briefly outline the procedures used to detect ELGsin the PEARS grism data, using a 2D–detection methodthat takes advantage of the observation that emissionlines typically originate from clumpy knots of star for-mation within galaxies. A detailed description of thismethod and comparison with several other extractionmethods are given in Straughn et al. (2008).
Data Pre-Processing
The first step in the grism data reduction involves pre–processing of the grism data. Each grism image is medianfiltered and smoothed using a 13 x 3 smoothing kernelalong the direction of the dispersion axis (i.e. unsharp-masked). We refer to Meurer et al. (2007) for a full de-scription of this method of pre–processing ACS grismdata in general. The dimension of smoothing kernal useddoes not greatly affect the sources that are selected. Thechoice of 13x3 smoothing kernel ensures efficient detec-tion of real emission-line objects while largely avoiding
Fig. 1.—
Here we demonstrate the advantage of the 2D–detectionmethod outlined in this paper (and described in detail in Straughnet al. 2008) for PEARS Object 104992. The top panel shows thatcontinuum flux overwhelms the line when the spectrum of the entiregalaxy is extracted (as would be the case in 1D methods; see e.g.,Xu et al. 2007). However, the emission line at (observed-frame)7000˚A is clearly seen when extraction of an individual knot is per-formed (bottom panel). See Figure 12 for an image of this object. faint image defects or other contaminants to the sam-ple. This unsharp–masking step is performed in orderto largely remove the continuum flux from the dispersedimage, leaving behind sharp emission line features. Zero–order images of compact sources are excluded in the tri-angulation step, described in the next section. Resid-ual image defects are also retained, but are unique toeach roll angle and are thus excluded in the next stepsas described below. In doing this, we isolate the actualemission line which would ordinarily be washed out bythe continuum, and therefore missed in more traditional1D detection methods (see Figure 1). After the imagesare pre–processed in this manner, they are cataloguedwith the source extraction algorithm SExtractor (Bertin& Arnouts 1996), giving a list of compact sources. Anaverage of 820 compact sources are initially selected fromeach field in this manner.
Emission Line Detection by Triangulation
The basis of this method of 2D emission–line detec-tion and wavelength calibration relies on each source be-ing observed in more than one roll angle. The emittingsource is traced back along the dispersion direction foreach roll angle, and intersections of these traces are usedto obtain the real sky coordinates (RA, Dec), as well asthe wavelength solution for that emitting source (see alsoFigure 2 of Straughn et al. 2008). In this way, image de-fects are excluded from the selection, since they wouldnot ordinarily appear at the same physical location onthe grism images and map onto a “source” as describedhere. This procedure is applied to all roll angle pairs,such that each source—that has three position anglesobserved, for example—has three calculations made (i.e.PA1-PA2, PA1-PA3, PA2-PA3). The HUDF, which hasfour position angles observed, thus has six calculationsper source. This procedure produces the master catalogof ELG sources, which are then visually checked. In thisvisual confirmation step, there are occasional instanceswhere an emission–line candidate was present in all threeroll angles, and thus was included in the master catalog,but is not a genuine emission line. Such is the case forsome bright galaxies that have continuum “bumps” thatappear in the grism image as compact sources: i.e., falseline candidates. When examining the collapsed 1D spec-tra from the individual sources, it is clear which sourcesare genuine emission lines and which are not. The gen-uine lines are subsequently retained for each field andthe final wavelength for each line listed in Table 1 is ob-tained by averaging the results from the roll angle pairsdescribed here. Here we define our terminology, since ex-tractions were performed on individual galaxy “knots”:a galaxy can have several knots, and each knot can havemore than one line as allowed by the grism bandpass.An average of 90 knot candidates per field are retainedin the automated triangulation step, and an average of46 genuine knots per field are retained after the visualconfirmation step. This method produced a total of 320emission lines originating from 226 galaxy knots, within192 individual galaxies in the five total PEARS SouthFields.
Redshifts of Emission–Line Galaxies
For ELG knots that have only one emission line in theirspectra—which is the case for 68% of the galaxy knots—afirst–guess redshift is essential for line identification. Forthis we use the spectroscopic and photometric redshiftsfrom the GOODS–MUSIC catalog (Grazian et al. 2006and references therein). About 33% of the ELGs de-tected in the PEARS South Fields have spectroscopicredshifts and 85% have photometric redshifts. There isalmost complete overlap between the two catalogs—lessthan 3% of sources have spectroscopic redshifts but nophotometric redshifts. Where no spectroscopic or photo-metric redshift exists for a particular source, we matchour sources against the table of spectrophotometric red-shifts of Cohen et al. (2009, in preparation)—which aredetermined by using a combination of both the grismspectra and broad–band data (see also Cohen et al. 2009;Ryan et al. 2007). Spectra with strong lines, however, areoften assigned artificially high spectrophotometric red-shifts due to the presence of such lines that are absentfrom the template SEDs used. In total, there were 16galaxies that had only a spectrophotometric redshift, fiveof which had two lines in the observed wavelength inter-val and therefore had a grism redshift calculated based on the line ratio. Of the galaxies with a single line in thespectrum and only a spectrophotometric redshift, 3 hadspectrophotometric redshifts in concordance with the ob-served line and were used to deduce final identification.For the 31 objects with a single line where either no priorredshifts were available, or the spectrophotometric red-shifts do not agree with any of the likely line identifica-tions, no redshift was assigned.Line identification proceeds as follows. For galaxyknots that have both H α /[O iii ], [O iii ]/[O ii ], orC iii ]/C iv in the observed wavelenth range, the ratio ofthe observed line wavelengths is computed to obtain adirect line identification and redshift—without need ofa first–guess redshift. For galaxy knots with only a sin-gle line, the existing spectroscopic, photometric, or spec-trophotometric redshifts (in order of preference) fromGrazian et al. (2006) and Cohen et al. (2009, in prepara-tion) are used to determine the most likely identificationof the single line within the redshift and instrinsic grismerrors. Redshifts based on these identifications and mea-sured line positions are subsequently recalculated andgiven in Table 1.Line fluxes are derived using standard Gaussian fit-ting techniques and measured lines with S/N & &
3. Since the [O iii ] line—which is usually thestrongest of the lines we detect—is blended with H β dueto the grism spectral resolution, we fit two Gaussian com-ponents. In these two–component fits, the central wave-lengths of the [O iii ] and H β lines are constrained tohave the correct wavelength ratio. In order to reduce thenumber of free parameters that go into the fits of thelow–resolution grism spectra, we examine individuallya subsample of fifteen representative test case spectra,varying the ratio of H β –to–[O iii ] line widths from 0.1to 1 (noting that, from the 1D spectra, all [O iii ] linewidths are qualitatively larger than the weaker, blendedH β line widths). In these tests, we found that an aver-age H β line width of ∼ iii ] line widthgave the best quantitative statistical fits. For 67% ofthe spectra in which we detect an [O iii ] line, the χ im-proves when including the H β line in our fit. Of these,23% of H β lines had S/N > &
3) than for the general catalog due to the fact that theline is blended and thus inherently contaminated by the[O iii ] doublet, and so only the most secure H β lines areincluded. In all cases where it was possible to includeH β in the line fits—and where such inclusion resultedin improved fits—the H β line was weaker by a factor ofat least 2. Utilizing this composite [O iii ] + H β fittingtechnique results in 90 [O iii ] fluxes which are statisti-cally improved using the reduced χ metric, comparedto fitting the [O iii ] line alone. Thirty H β fluxes alsoresult from this method. RESULTS
In Table 1 we list the emission–line wavelengths, lineIDs, fluxes, and grism redshifts for 320 lines originat-ing from 226 star–forming knots within 192 individualgalaxies found in our search for ELGs in the PEARSSouth Fields. Of these, 25 galaxies (12%) exhibit multi-ple emitting knots, and 61 knots (27.0%) have two lines(thus providing secure redshifts; see Section 3). Our sam- Straughn et al.
Fig. 2.—
The distribution of ELG continuum magnitudes peaksaround i ′ AB ∼
24 mag for both the HUDF and the PEARS SouthFields 1—4 data. The HUDF distribution is somewhat more uni-form, owing in part to a larger fraction of faint objects due to itsgreater depth. The clumpy face–on spirals generally make up thebright end of the magnitude distribution, while many of the HUDFsources comprise most of the faint end. ple includes 136 [O iii ], 83 H α , 30 [O ii ], 30 H β , 4 C iv ,3 C iii ], 2 MgII, 1 H γ , and 1 NeIII lines (see Table 3).Of these galaxies, 17 are CDF-S X-ray sources (Giac-coni et al. 2002; Grogin et al. 2009, in preparation). Themost common lines (H α , [O iii ], and [O ii ]) are detectablein the redshift ranges of 0–0.4, 0.1–1.1, and 0.4–1.5 re-spectively, given the grism band–pass. The [O iii ] emit-ters have, in general, very high equivalent widths, with amean rest frame equivalent width EW [ OIII ] ,mean = 152˚ A at a redshift of z ∼ α , [O iii ], and [O ii ] lines are shown in Figure 4.Figure 2 shows the i ′ AB -band continuum magnitudedistribution of the 192 ELGs in the PEARS South fields.The distribution peaks around i ′ AB =24 mag for boththe HUDF and the PEARS South Fields 1–4, althoughthe falloff at fainter magnitudes is more pronounced forthe shallower South Fields 1–4 data. The 2D method de-scribed here is optimized to find distinct emitting knotsthat often are present in relatively bright galaxies—forexample, face–on spirals with large star–forming regions.These generally make up the bright-end of the magnitudedistribution shown here. The fainter tail of the magni-tude distribution is comprised largely of objects from thedeeper HUDF pointing. The distribution of emission–line fluxes for all 320 emission lines, regardless of species,is shown in Figure 3. Figure 5 shows that distributionfor each of the three most common emission lines in oursample: H α , [O ii ], and [O iii ]. The flux distribution forthe sample peaks at ∼ × − ergs cm − s − for the20–orbit/field PEARS data (four fields) and falls off atlower values due to incompleteness of the data (Figure5). The peak is at a slightly fainter flux for the deeperPEARS HUDF at ∼ × − ergs cm − s − .Given the ACS grism resolution, contamination of thedominant lines by other nearby, unresolved lines is almostcertainly present. For example, the H α line flux mea-surements will contain some contribution from the [NII] λλ Fig. 3.—
The distribution of ELG emission–line fluxes peaks at ∼ × − ergs cm − s − for the PEARS South Fields 1–4 (20HST orbits per field) and at ∼ × − ergs cm − s − for thedeeper (40 HST orbits) PEARS HUDF. et al. (2004) derive an [NII] correction as a function of R band luminosity using the Nearby Field Galaxy Sam-ple of spiral and irregular galaxies (Jansen et al. 2000).Other grism surveys of ELGs have used global correctionsby Gallego et al. (1997), which also was derived based ona local galaxy sample. Our detection method serves toproduce individual galaxy knots in a wide array of mor-phological types (as described in Section 3), and thusa global adoption of any one [NII] contamination cor-rection is not straightforward. Therefore, the measuredH α fluxes are likely overestimates due to this contam-ination but we do not adopt a global correction. Theamount of contamination can range from a few percentfor, e.g., blue compact dwarf galaxies, which have un-usually high ionization and low metallicity, to the fac-tors of 0.3 and 0.5 assigned by Gallego et al. (1997) andKennicutt (1992) respectively (however, the latter beingfor massive, metal–rich galaxies). For the Nearby FieldGalaxy Survey (Jansen et al. 2000), [NII]/H α ranges be-tween 0.03–0.5 with a mean value of 0.27. The signal-to-noise (S/N) distribution of the emission line fluxes isshown in Figure 6. The average S/N for the sample is11.8. This increases to 12.6 when the generally weaker,blended H β line measurements are excluded. Our de-tection methods outlined above serve to produce a finalsample of high-confidence detections.The presence of dust affects our measurements, andthus the calculations of, e.g., the star–formation rate(Section 4.4.3) should be considered lower limits becauseno extinction correction was applied. The H β flux inprinciple allows an estimation of extinction for the casesin which both H β and H α fall into the wavelength rangeof the grism and including H β results in a quanitativelybetter fit. This is only possible for a very small percent-age of objects and thus we do not apply a global cor-rection based on only these few sources. Both H α andH β are measured in the spectra of objects 38750, 40816,75753, 78582, and 123859. However, objects 40816 and78582 are both X–ray sources and therefore likely AGNcandidates (see Section 4.3). Because of this, the emis-sion line fluxes of these two sources are likely affected bythe potential AGN component. Using only the Balmer Fig. 4.—
The distribution of rest–frame equivalent widths ofthe three most common emission lines in our sample. The medianequivalent widths are 119˚A, 73˚A, and 36˚A for [O iii ], H α , and [O ii ]respectively. The average redshifts of the three species is shown. decrement and the Milky Way or LMC extinction lawfrom Seaton (1979)—e.g., Calzetti et al. 1994, who findan average E(B-V) of 0.4 for starburst galaxies—givesE(B-V) values of 0.60, 0.26, and 0.50 for objects 38750,75753, and 123869 (e.g., those not X–ray detected) re-spectively. Grism Redshifts
Of the 192 emission–line galaxies, 118 have new grismspectroscopic redshifts based on our line identifications.We find 8 galaxies (Table 1) that previously had no re-ported redshift and that have two lines, allowing deter-mination of a grism redshift from the wavelength ratios.The redshift distribution of the sample is given in Fig-ure 7. The redshift distribution peaks at z ∼ iii ], H α , and [O ii ]. This explains thelower redshift peak compared to the peak in the generalfield galaxy redshift distribution. The few high–redshiftobjects in this plot are the more rare C iii ], C iv , andMgII line emitters. All of these high–redshift sources inthe CDF–S are detected in the X–ray observations, andare thus likely AGN (Grogin et al. 2009, in preparation).The CDF-S X-ray sources are noted in Table 1. Fig. 5.—
The emission–line flux distributions peak at ∼ × − ergs cm − s − , ∼ × − ergs cm − s − , and ∼ × − ergs cm − s − for H α , [O iii ], and [O ii ] respectively for the20–orbit/field PEARS data (four fields). The PEARS HUDF linefluxes peak at slightly fainter values ( ∼ × − ergs cm − s − for [O iii ] and ∼ × − ergs cm − s − for [O ii ]). Fig. 6.—
Distribution of signal–to–noise for all derived line fluxes.The average S/N for the sample is 11.8. This average increases toS/N=12.3 when the weaker, blended H β lines are excluded. Ourdetection method requires a relatively high S/N because the initialgrism detection images are smoothed before source extraction isperformed. This is the reason we miss, e.g., lower S/N Ly α emitters(Rhoads et al. 2009). Straughn et al.
Fig. 7.—
Emission–line galaxy redshift distribution. The G800Lgrism is sensitive from 6000-9500 ˚A, which yields the most commonemssion lines—H α , [O iii ], and [O ii ] in the wavelength ranges ofz=0–0.4, 0.1–1.1, and 0.4–1.5 respectively. The [O iii ] line is themost common, and thus the peak is near z ∼ iii ], C iv , and MgII emitters. In Figure 8 we show comparisons of our calculatedgrism redshifts to the available photometric and spectro-scopic redshifts for the ELGs. As mentioned, for objectswith only a single emission line, any previously availableredshift was used to initially identify the line. This wasaccomplished in the cases where the line wavelength fallswithin the expected wavelength based on that object’spreviously–measured redshift, within the redshift (andinherent grism) errors.Comparison of grism–spectroscopic redshifts computedhere to previously–existing spectroscopic redshifts servesto demonstrate the wavelength accuracy of the grism,which is shown in Figure 8. The dispersion about themean is 0.005 and two objects are & σ outliers: PEARSObjects 72509 and 17362, both of which are single–linedetections with relatively low S/N < σ outlier). This objecthas two emission lines with S/N >
5, providing a securegrism redshift based on the wavelength ratio. Object20201, which was only marginally within 3 σ of the pho-tometric redshift also has two high S/N emission lines,as well as a clear H β “bump” in the [O iii ] line pro-file, further confirming its identification (Figure 9). Thusfor these two outlying objects, we are confident that thegrism redshift calculated here is correct. Line Luminosities & Star–formation Rates of theELGs
Table 1 lists the line luminosities for the objects in oursample. The median H α line luminosity is 8.3 × ergss − , and the lowest luminosity is 2.5 × ergs s − . Asa comparison, Drozdovsky et al. (2005) find a median H α line luminosity of 2.7 × ergs s − from the ACS GrismParallel Survey. The typical local L ∗ (H α )=7.1 × ergss − (Gallego et al. 1995) and L ∗ (H α )=3.6 × ergs s − at z=1.3 (Yan et al. 1999). The median [O iii ] and [O ii ]line luminosities are 2.8 × ergs s − and 6.7 × ergs Fig. 8.—
Comparison of available spectroscopic (top panel) andphotometric (bottom panel) redshifts to the PEARS grism red-shifts measured in this study, with 3 σ (dashed) lines shown. 31%and 81% of PEARS-South ELGs have previously–measured spec-troscopic and photometric redshifts, respectively. Comparison ofgrism to spectroscopic redshifts essentially serves to demonstratethe wavelength / redshift calibration accuracy of the PEARS grismdata. See section 4 for a discussion on outliers. s − respectively. About 96% of our emitting regions haveluminosities L & ergs s − .We present the star-formation rate (SFR) as a functionof redshift of our ELG sample in Figure 10. SFRs arecalculated using the calibrations of Kennicutt (1998) forH α and [O ii ]:SFRH α (M ⊙ yr − )=7.9 × − L(H α ) (erg s − ) (1)SFR [ OII ] (M ⊙ yr − )=1.4 × − L([OII]) (erg s − ) (2)respectively for solar abundances and a Salpeter IMFfor 0.1-100M ⊙ . The H α luminosity is a direct mea-sure of the ionizing output of a stellar population (un-der case–B recombination) and thus can be related di- Fig. 9.—
An example spectrum from PEARS Object 20201 at aredshift of z=0.445, exhibiting the blending of H β and [O iii ]. H α isalso visible near the red end of the spectrum. An H β “bump” isclearly seen near 7000˚A, though not resolved from the stronger[O iii ] blend. In total, 31 galaxy spectra had better χ fits whenthe H β line was included. H γ and marginal H δ are detected here,near 6300˚A and 6000˚A respectively. rectly to the massive star–formation rate. In particu-lar, it probes the formation of the ionizing O stars, andthus is the most secure line in determining the SFRs.The SFR based on [O ii ] line luminosity is less secure, asdifferences in metallicity and other local environmentalproperties play a larger role in the oxygen lines (Kewleyet al. 2001; Jansen et al. 2001; Kewley et al. 2004). Ken-nicutt (1998), for example, reports a ∼
30% uncertaintyon the [O ii ] SFR calibration. However, the [O ii ] lineis still calibrated well enough to deduce SFRs for galax-ies at higher redshift (Cowie et al. 1996, Kennicutt 1992,Gallagher et al. 1989). We use the Kennicutt (1998) cal-ibrations for the H α and [O ii ] emitters in the PEARS-South ELG sample presented here.The determination of SFRs from [O iii ] line luminosi-ties is not as straightforward, since the [O iii ] flux de-pends quite strongly on metallicity and gas tempera-ture (Kennicutt et al. 2000, Kennicutt 1992), and SFRsderived from the [O iii ] λ iii ] line has been usedto gain crude lower limits on the SFR (Maschiettoet al. 2008; see also Teplitz et al. 2000 for a discussionof [O iii ] SFRs for LBGs). Maschietto et al. (2008) ar-rive at a lower limit of SFR [ OIII ](5007) (M ⊙ yr − ) < × − L([
O iii ]) ergs s − for their sample of 13 star–forming galaxies. With the ACS G800L grism resolution,the [O iii ] λλ β are blended, andwhile our fitting technique does fit the blended [O iii ]+H β feature, some cross–contamination of the lines islikely. Many of the galaxy knots that contain [O iii ]emission originating from star–formation (and not fromAGN as described in Sec. 4.3) also have either H α or[O ii ] lines in their spectra, so in these cases, it is clearlybest to use the more direct H α – or [O ii ]–deduced SFR.For the emitting regions in which only an [O iii ] line isdetected—due to the H α or [O ii ] lines falling out of thegrism bandpass—we derive the [O iii ] SFR by using the[O iii ]:H α ratio from the galaxy knots that do have both Fig. 10.—
Star formation rates as a function of redshift basedon the line luminosities of the ELGs. We see the expected bias ofhigher SFRs at higher redshifts, due to the detection limits. TheseSFRs are uncorrected for extinction and are thus lower limits. Theapproximate empirical detection limit—derived from the averagelimiting flux of all three lines—is shown for the (deepest) PEARSHUDF data. emitting lines. Since the [O iii ] λλ × L [ O iii ] in order to estimate thecontribution from the λ [ OIII ] (M ⊙ yr − )=(6.4 ± × − L([OIII]) (ergs − ) (3)While there is large scatter in the [O iii ]–derived SFR,we find no indication of nonlinearity in the relation ofH α and [O iii ] for this subsample of ELGs. The possi-ble presence of residual blended H β flux described aboveprovides an additional source of error to the [O iii ] fluxderivation. However, in all cases, we did not applyextinction corrections, and thus the implied SFRs pre-sented here are in general lower limits. In addition,we assume that most of the galaxies’ active star forma-tion is occurring in these emission–line regions, but notethat the sample is incomplete in the sense that only thebrightest knots of the galaxies are detected, and diffuseemission is missed in our method. Figure 10 shows theexpected bias of lower SFRs at lower redshift. This ingeneral follows calculations performed in similar studies,e.g., Drozdovsky et al. 2005, who computed SFRs of agrism–selected sample of ELGs. Potential AGN Candidates Among the ELGSample
Adjusting our line fitting algorithm to include H β fitsallows us to gain a crude estimate of excitation. In Fig-ure 11, we show the [O iii ]:H β line ratio compared toa large sample of SDSS AGN. Kauffmann et al. (2003)compare this line ratio to [NII] λ / H α and thus de-fine a region of likely AGN (as compared to starburstgalaxies) in a BPT diagram (Baldwin, Phillips, & Ter-levich 1981; see also Kewley et al. 2001). In the grismdata, the [NII] line is blended with H α and is not possi-ble to deblend, as is the case with some objects for [O iii ] Straughn et al.and H β , and thus a BPT diagram is not possible to con-struct from the PEARS ELGs. However, starburst galax-ies with [O iii ]:H β ≥ iii ] doublet—are extremely rare based on thestarburst/AGN demarcations made by both Kauffmannet al. (2003) and Kewley et al. (2001), which include ef-fects of metallicity and dust. We thus conclude that thePEARS objects that lie above this threshhold are poten-tial AGN candidates among our ELG sample. There area total of 27 ELGs that have both [O iii ] and H β mea-sured in at least one of their knots. Of these, 3 haveF([O iii ])/F(H β ) ≥ iii ])/F(H β ) ≥ iii ]:H β line ratios, high X–ray luminosities are also strong indicators of AGN ac-tivity. Grogin et al. (2007) and Grogin et al. (2009, inpreparation) investigate CDF X–ray sources that fallwithin the PEARS area. In total, 17 of the emission–linesources detected in this study overlap with the Groginet al. PEARS X–ray sample. Of these 17, 8 objects haveX–ray luminosities L X ≥ ergs s − and are thus likelyAGN. These L X ≥ ergs s − sources display mainlythe expected AGN lines (e.g., C iii ], C iv , and [MgII]).All matches to CDF-S X-ray sources are noted in Table1. Of the PEARS emission–line sources with both the[O iii ] and H β lines measured, two are also X–ray sources(Grogin et al. 2009, in preparation), but with L X < ergs s − . One of these two objects, PEARS Ob-ject 40816 at redshift z=0.281, has a quite high fluxratio F([O iii ]) / F(H β )=12.6 and an X–ray luminosityof L X =2 . × ergs s − . Object 40816’s line emis-sion originates from the galaxy’s nucleus. The galaxyappears to be interacting with a nearby disk galaxy(PEARS Object 35818) with a tidal stream in betweenthe two objects. Given this PEARS Object 40816’shigh F([O iii ]) / F(H β ) and moderate L X values, onecan interpret this source as being a potential obscuredinteraction–induced AGN. The other object, PEARSObject 78582 with redshift z=0.454, has a flux ra-tio F([O iii ]) / F(H β )=3.2 and L X =1 . × ergs s − .This source appears spheroidal with signs of tidal de-bris and/or interaction with PEARS Object 78762. Ob-ject 78582 is thus likely a regular star–forming galaxywith starburst–related X–ray emission, given its lowerF([O iii ]) / F(H β ) value. As Figure 11 demonstrates, thePEARS AGN candidates based on the [O iii ]:H β ratioreside mainly on the upper right locus of the SDSS sam-ple (black dots). The lack of objects with lower excita-tion is likely a result of the de–blending of the [O iii ] andH β lines—as was noted in Section 3.3, the H β line wasweaker by a factor of at least 2 in spectra where bothlines were fit. We thus conclude that inclusion of H β inthe line fitting procedure when possible provides a wayin which to select probable AGN from the grism data forfollow–up study and confirmation. High–redshift Star–forming Regions
One of the main advantages of the 2D–detectionmethod used for this study is the detection of emissionlines in distinct star–forming regions within galaxies atintermediate redshift—regions that would not have been
Fig. 11.— [O iii ] to H β flux ratios of PEARS ELGs (red di-amonds) compared to those from the SDSS AGN catalog (dots;Kauffmann et al. 2003). As discussed in Sec. 4, the PEARS ob-jects with [O iii ]:H β & iii ] and H β measured (PEARS Objects 40816 and 78582). detected if the spectrum of the entire galaxy was ex-tracted (Figure 1). In ∼
12% of galaxies we find multipleemitting knots (Figure 12). Many of these multiple–knotemitters are clumpy spirals with distinct star–forming re-gions. In total, 25 galaxies have multiple emitting knots.Within these galaxies, there are 59 such knots with 83emission lines total—the majority of which are H α . Themedian redshift of the subsample of multiple–emittingknot ELGs is z=0.336, and the highest redshift multiple–knot emitter is at z=0.653. While properties of localindividual HII regions have been studied for some time(e.g., Hodge 1969; Shields 1974; Shields 1990; McCall,Rybski, & Shields 1985; Zaritsky, Kennicutt, & Huchra1994; Gordon et al. 2004; Kennicutt 1984), grism sur-veys such as PEARS—combined with the 2D–detectionmethod used here—are useful for finding spectra of in-dividual intermediate–redshift star–forming regions. Asdiscussed in Section 4.2, our detection limit serves toproduce a sample of mostly giant star–forming regions,which have been studied extensively in the local universesince they are sites of the most extreme star formationknown (e.g., Shields 1990; Giannakopoulou-Creightonet al. 1999). We find that within an individual galaxy,the H α –derived SFR typically differs by a factor of twoor three between knots. The most extreme differences inSFRs across individual galaxies do not occur in the face–on spirals that are quite common in the subsample ofmultiple–emitting knot galaxies, but in clumpy galaxieswith clear merger signatures. This effect is not unex-pected, since mergers are known to induce enhanced starformation activity which is revealed through the galaxies’emission lines. Regions of the galaxy that are undergo-ing more intense physical alterations due to the mergingactivity presumably exhibit more intense star formation.One of the questions that can be addressed throughthe 2D–detection technique concerns how the galaxies’giant star–forming knots are distributed radially withineach galaxy. As with giant HII regions generally, theseradial distribution studies have typically been performedon nearby spiral galaxies (Hodge 1969; Hodge & Ken-nicutt 1983; Athanassoula et al. 1993, Gonzalez Delgado Fig. 12.—
Subset of PEARS ELGs with multiple emitting knotsas described in Section 4.3, from which the radial distribution ofstar–forming knots is derived. PEARS IDs are given in upper–leftcorners of stamps, which are 5 arcsec on a side. Circles indicateregion of line emission (colored circles are for visual aid only inbright regions). The automated 2D–detection method is optimizedto detect line emission in galaxy knots as shown here. The radialdistribution of the galaxy knots shown here is given in Figure 13. & Perez 1997) with normal (e.g., not giant) HII regions.Since the grism data and detection method used hereis optimized to find the brightest star–forming regionsonly, a direct comparison to these studies is not straight-forward. However, we examine here a subset of tenof the multiple–knot emitters—excluding visually dis-turbed galaxies such as mergers and objects with nearbycompanions—in order to determine the radial distribu-tion of HII regions. We exclude irregular galaxies and/ormergers—that could have emitting knots in the tidal tail,for example—since such enhanced star formation is likelyinduced predominantly by the dynamics of the interac-tion and not that which normally occurs in undisturbeddisk galaxies. Such exclusion of irregular galaxies in ra-dial distribution studies was also done by, e.g., Athanas-soula et al. (1993). This subset of ten galaxies with mul-tiple emitting knots contains a total of 26 knots, withina redshift range of 0.076–0.483 (seven of which are abovez & SUMMARY
We present results from a search for emission–linegalaxies in the five PEARS South Fields, including theHUDF. We outline briefly the method used to arrive atour catalog, which relies on spectral extractions from in-
Fig. 13.—
Comparison of radial distributions of star–formingregions within the PEARS galaxies that have multiple (giant) star–forming knots to a sample of local galaxies with well–known giantHII regions. Radial knot distances are all scaled to the half–lightradii of the galaxy, as described in detail in the text. A few ofthe PEARS knots shown here could be considered nuclear. ThePEARS sample of galaxies with multiple–emitting knots has anaverage redshift of z=0.242, and both samples peak near the half–light radius. dividual emitting knots within galaxies, detected first inthe 2D grism image. In this way, we detect emission–line sources that would likely otherwise be missed in thestandard extraction of entire galaxies, where continuumflux can often dominate the spectrum and wash out theline. Here we summarize our findings:1. We detect 320 emission lines from 226 galaxy knotswithin 192 individual galaxies. The most common emis-sion lines are [O iii ], H α and [O ii ]–we detect 136, 83,and 30 emission lines of each species, respectively. Wedetect 25 galaxies with multiple emitting knots.2. In Table 1 we present 118 new grism spectroscopicredshifts in the GOODS–South Field. Line identifica-tions are obtained by either wavelength ratios where twolines are present in a given spectrum, or by utilizing pre-viously measured—typically photometric—redshifts forthese objects as a first–guess.3. We calculate SFRs of the ELG sample using H α and[O ii ] where available, and derive an [O iii ] SFR based onthe more dependable lines when two lines are availablein the spectra. The SFR as a function of redshift is givenin Figure 10.4. Including blended H β in our line fits results in iden-tification of probable AGN based on approximate exci-tation levels. In comparison to AGN from SDSS, we findthat the PEARS AGN candidates are situated in thehigh–excitation, high–luminosity region of the distribu-tion.5. 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TABLE 1Global Properties of Emission–Line Galaxies
PEARS Knot RA Dec i ′ AB Wavelength Flux EW Line Grism FlagID − erg/s/cm ) (˚A) ID Redshift (*)9359 1 53.1682091 -27.9300213 22.97 7349 21.2 ± α ± α ± iii ] 0.337 112250 1 53.1566811 -27.9257526 24.72 8774 26.1 ± α ± · · · · · · · · · ± iii ] 0.370 113541 1 53.1584473 -27.9188538 21.49 9059 75.7 ± α ± iii ] 0.370 113541 2 53.1584740 -27.9189358 21.49 9013 95.6 ± α TABLE 1 — Continued
PEARS Knot RA Dec i ′ AB Wavelength Flux EW Line Grism FlagID − erg/s/cm ) (˚A) ID Redshift (*)13553 1 53.1643639 -27.9186115 19.46 7416 23.0 ± α ± iii ] 0.621 314215 ‡ ± ii ] 0.832 114215 ‡ ± iii ] 0.832 115116 1 53.1471062 -27.9200668 25.61 6618 80.4 ± iii ] 0.332 115116 1 53.1471062 -27.9200668 25.61 8742 22.4 ± α ± β ± iii ] 0.659 317024 1 53.1534920 -27.9139519 22.20 8070 3.8 ± β ± iii ] 0.659 217362 1 53.1624565 -27.9140434 22.56 7367 8.1 ± iii ] 0.475 217587 1 53.1607971 -27.9138756 24.82 8240 21.3 ± iii ] 0.650 318337 1 53.1779099 -27.9095287 22.25 7900 35.0 ± ii ] 1.120 218410 1 53.1801987 -27.9110069 22.55 7086 4.9 ± β ± iii ] 0.454 319422 1 53.1720695 -27.9096584 24.52 7757 44.6 ± iii ] 0.553 319546 1 53.1468811 -27.9090500 23.61 9049 20.2 ± ii ] 1.428 219639 1 53.1456108 -27.9038506 19.92 8399 62.0 ± α ± iii ] 0.445 120201 1 53.1496544 -27.9078388 24.14 9514 52.7 ± α ± ii ] 1.188 221754 1 53.1799278 -27.9038067 24.07 7802 19.2 ± iii ] 0.562 322203 1 53.1505966 -27.9024887 22.13 6330 183.8 ± iii ] 0.267 122203 1 53.1505966 -27.9024887 22.13 8427 91.9 ± α ± · · · · · · · · · ± · · · · · · · · · ± iii ] 0.559 326009 1 53.1379280 -27.8946438 23.63 7163 62.0 ± iii ] 0.439 326107 1 53.1397209 -27.8947048 25.48 8443 36.9 ± · · · · · · · · · ± β ± iii ] 0.679 126009 1 53.1379280 -27.8946438 23.02 9441 18.7 ± α ± iii ] 0.439 127293 1 53.1968880 -27.8927078 25.89 7693 18.1 ± · · · · · · · · · ± · · · · · · · · · ± β ± iii ] 0.665 332905 1 53.1583290 -27.8816776 23.89 7451 12.9 ± ii ] 0.999 333086 ‡ ± ‡ ± ± ii ] 1.047 233355 1 53.1859474 -27.8796978 23.19 7083 47.7 ± · · · · · · · · · ± α ‡ ± ‡ ± ± · · · · · · · · · ± β ± iii ] 0.408 138750 1 53.1655579 -27.8651085 20.82 9345 93.9 ± α ± iii ] 0.353 139387 1 53.1705093 -27.8666763 21.31 8881 37.3 ± α ± iii ] 0.706 340163 1 53.1791611 -27.8665504 24.06 9474 19.2 ± iii ] 0.897 240816 † ± β † ± iii ] 0.281 140816 † ± α ± ii ] 0.866 141078 1 53.1807861 -27.8651638 24.30 9316 38.0 ± iii ] 0.866 143170 1 53.1561699 -27.8608074 24.06 8451 53.6 ± iii ] 0.692 345223 1 53.1973305 -27.8572559 24.48 8106 5.3 ± β ± iii ] 0.668 345454 1 53.1814690 -27.8563213 22.75 7105 9.7 ± iii ] 0.425 146562 1 53.1642036 -27.8534393 23.03 8319 22.7 ± iii ] 0.665 346994 1 53.1643944 -27.8536777 24.22 8108 7.2 ± β ± iii ] 0.668 348890 1 53.2069473 -27.8480740 23.07 7110 15.7 ± ii ] 0.908 148890 1 53.2069473 -27.8480740 23.07 9566 38.9 ± iii ] 0.908 149766 1 53.1751556 -27.8476467 23.57 6059 20.3 ± iii ] 0.213 149766 1 53.1751556 -27.8476467 23.57 8041 11.6 ± α ± iii ] 0.580 351356 1 53.1567993 -27.8429546 21.59 8126 20.5 ± iii ] 0.627 451976 1 53.2045479 -27.8425064 23.73 9280 56.0 ± iii ] 0.862 151976 1 53.2045479 -27.8425064 23.73 6939 14.8 ± ii ] 0.86 1 TABLE 1 — Continued
PEARS Knot RA Dec i ′ AB Wavelength Flux EW Line Grism FlagID − erg/s/cm ) (˚A) ID Redshift (*)52086 1 53.1578102 -27.8444538 23.53 4954 4.1 ± β ± iii ] 0.526 352086 2 53.1577988 -27.8443146 23.53 7419 6.6 ± β ± iii ] 0.526 352398 1 53.1938133 -27.8442917 24.19 8323 12.7 ± · · · · · · · · · ± iii ] 0.445 152502 1 53.2011223 -27.8412380 21.53 9485 29.9 ± α ± iii ] 0.562 254022 1 53.1747398 -27.8407822 22.37 6669 18.0 ± iii ] 0.336 154022 1 53.1747398 -27.8407822 22.37 8769 20.0 ± α ± β ± iii ] 0.336 155102 1 53.1756477 -27.8385963 21.85 7224 30.2 ± iii ] 0.458 255102 2 53.1757545 -27.8387928 21.85 7281 34.5 ± iii ] 0.458 256801 1 53.1450958 -27.8373871 23.96 8040 7.5 ± β ± iii ] 0.653 356875 1 53.1529732 -27.8376999 24.52 7695 11.7 ± iii ] 0.541 358985 1 53.1999168 -27.8340626 23.78 7807 23.2 ± iii ] 0.563 359018 1 53.1763496 -27.8306465 20.63 9606 56.5 ± α ± · · · · · · · · · ± iii ] 0.542 263612 1 53.1554031 -27.8261337 25.33 7820 3.3 ± β ± iii ] 0.606 366061 ‡ ± ± iii ] 0.526 370314 1 53.1748161 -27.7995949 20.36 7526 28.4 ± α ± α ± ii ] 0.830 170337 1 53.1938210 -27.8128853 23.40 9142 38.7 ± iii ] 0.830 170407 † ± α † ± α ± iii ] 0.212 170651 1 53.1530495 -27.8121529 23.33 7956 30.4 ± α ± iii ] 0.759 371924 1 53.1536827 -27.8088989 23.84 6898 3.6 ± iii ] 0.381 372179 1 53.1310501 -27.8084450 23.34 6281 29.1 ± iii ] 0.257 372509 1 53.1705208 -27.8066082 24.53 8548 7.1 ± ii ] 1.294 272557 1 53.1338768 -27.8068733 23.56 6673 15.7 ± · · · · · · · · · ± iii ] 0.652 374234 1 53.1377335 -27.8042202 25.95 7492 2.7 ± β ± iii ] 0.542 375506 1 53.1472664 -27.8008537 26.26 8419 17.1 ± α ± iii ] 0.277 175547 1 53.1733017 -27.7993031 23.78 7372 7.8 ± α ± α ± β ± iii ] 0.343 175753 1 53.1872597 -27.7943401 22.29 8816 32.8 ± α ± β ± iii ] 0.343 175753 2 53.1873703 -27.7942238 22.29 8819 65.5 ± α ± α ± iii ] 0.343 176154 1 53.1512299 -27.7987995 23.73 8016 39.9 ± iii ] 0.600 377558 1 53.1864052 -27.7910328 18.67 7995 23.1 ± · · · · · · · · · · · · ± · · · · · · · · · · · · ± ii ] 1.071 378021 1 53.1839218 -27.7954350 27.62 8615 13.3 ± ii ] 1.311 378077 1 53.1841545 -27.7926388 21.73 6482 48.2 ± ii ] 0.737 178077 1 53.1841545 -27.7926388 21.73 8675 69.7 ± iii ] 0.737 178237 1 53.1876869 -27.7943954 20.50 6693 14.4 ± iii ] 0.340 178237 1 53.1876869 -27.7943954 20.50 8800 38.7 ± α ± iii ] 0.340 178237 3 53.1877136 -27.7942200 20.50 7872 20.6 ± · · · · · · · · · ± · · · · · · · · · ± α ± iii ] 0.234 178491 3 53.1547127 -27.7931709 22.70 6114 54.5 ± iii ] 0.234 178491 3 53.1547127 -27.7931709 22.70 8080 20.4 ± α † ± β † ± iii ] 0.454 178582 † ± α ± iii ] 0.458 379283 1 53.1419983 -27.7867641 20.76 8070 19.3 ± α TABLE 1 — Continued
PEARS Knot RA Dec i ′ AB Wavelength Flux EW Line Grism FlagID − erg/s/cm ) (˚A) ID Redshift (*)79283 2 53.1421967 -27.7865429 20.76 8059 37.7 ± · · · H α ± iii ] 0.375 379483 † ± α † ± α † ± iii ] 0.438 179520 1 53.1861954 -27.7916622 26.73 8703 11.3 ± iii ] 0.742 380071 1 53.1866226 -27.7902203 27.06 7335 47.2 ± α ± · · · [O ii ] 0.953 380500 1 53.1472092 -27.7884693 23.36 8064 4.0 ± β ± iii ] 0.658 180500 1 53.1472092 -27.7884693 23.36 6178 11.8 ± ii ] 0.658 180666 1 53.1765137 -27.7897243 25.04 6849 3.0 ± β ± iii ] 0.411 381032 1 53.1815071 -27.7879314 23.36 6045 34.1 ± iii ] 0.210 281256 1 53.1920815 -27.7872849 23.05 7841 7.9 ± ii ] 1.104 381609 1 53.1640930 -27.7872963 24.37 7820 15.7 ± ii ] 1.098 381944 1 53.1446838 -27.7855377 22.53 8138 62.1 ± α ± iii ] 0.228 181944 2 53.1447372 -27.7854137 22.53 8129 162.1 ± α ± · · · [O iii ] 0.475 383381 1 53.1765251 -27.7825947 24.96 6640 25.3 ± iii ] 0.329 383553 ‡ ± ‡ ± ± ii ] 0.837 383789 1 53.1527901 -27.7826843 24.81 8862 36.8 ± iii ] 0.774 283804 1 53.1845818 -27.7833576 25.04 7918 9.0 ± ii ] 1.125 383834 1 53.1580925 -27.7812119 21.95 8102 10.8 ± iii ] 0.622 385517 1 53.1763344 -27.7808685 24.85 7409 3.1 ± β ± iii ] 0.530 185844 1 53.1624680 -27.7803612 26.19 8569 22.4 ± ii ] 1.299 387294 1 53.1629181 -27.7752514 21.03 8192 8.0 ± α ± α ± iii ] 0.130 187658 1 53.1477661 -27.7769241 24.06 7854 7.8 ± ii ] 1.107 288580 1 53.1620064 -27.7740345 22.65 6354 10.3 ± iii ] 0.269 388580 2 53.1619110 -27.7738514 22.65 6338 30.5 ± iii ] 0.269 389030 1 53.1604347 -27.7752380 21.74 9127 32.3 ± ii ] 1.449 389209 1 53.1503944 -27.7720318 21.27 6075 26.2 ± iii ] 0.216 189209 1 53.1503944 -27.7720318 21.27 8000 26.2 ± α ± α ± α ± iii ] 0.630 390246 1 53.1512070 -27.7728481 24.08 8008 20.0 ± iii ] 0.603 391205 1 53.1505280 -27.7713089 21.27 7857 26.6 ± · · · · · · · · · ± iii ] 0.533 392839 ‡ · · · · · · MgII 1.215 294632 1 53.1795502 -27.7662010 25.05 8310 14.1 ± iii ] 0.664 395471 1 53.1773453 -27.7639313 22.40 8002 23.2 ± α ± iii ] 0.535 296627 1 53.1704559 -27.7614193 21.53 7453 30.7 ± α ± iii ] 0.963 297655 1 53.1140289 -27.7612534 23.72 7502 9.9 ± β ± iii ] 0.543 3100188 1 53.1012573 -27.7568226 25.07 6353 7.2 ± β ± iii ] 0.311 1100188 1 53.1012573 -27.7568226 25.07 8603 32.3 ± α ‡ ± ‡ ± γ ± ii ] 0.977 1103116 1 53.1055984 -27.7507782 22.76 9900 59.3 ± iii ] 0.977 1103422 1 53.1073837 -27.7498055 23.01 6826 20.4 ± ii ] 0.832 1103422 1 53.1073837 -27.7498055 23.01 9141 25.1 ± iii ] 0.832 1104408 1 53.1160088 -27.7471771 24.26 8677 25.4 ± iii ] 0.737 3104849 † ± α † ± α † ± α † ± α † ± α † ± α ± α ± α ± α ± α TABLE 1 — Continued
PEARS Knot RA Dec i ′ AB Wavelength Flux EW Line Grism FlagID − erg/s/cm ) (˚A) ID Redshift (*)104992 5 53.1178970 -27.7405090 19.65 7055 27.0 ± α ± α ± α ± α ± iii ] 0.336 1106136 1 53.1138039 -27.7442055 24.40 8766 13.1 ± α ± iii ] 0.337 1106491 1 53.1136703 -27.7437534 25.04 8777 14.1 ± α ± · · · · · · · · · ± α ± iii ] 0.313 1108642 2 53.0944328 -27.7341805 21.48 6524 141.4 ± iii ] 0.313 1108642 2 53.0944328 -27.7341805 21.48 8617 101.1 ± α ± α ± iii ] 0.365 1109547 1 53.0892677 -27.7360077 24.96 6809 38.2 ± iii ] 0.368 1109547 1 53.0892677 -27.7360077 24.96 8978 18.8 ± α ± iii ] 0.368 1109652 1 53.0903625 -27.7367249 21.64 8975 18.5 ± α ± ii ] 0.744 1109900 1 53.1128082 -27.7346249 22.42 8731 10.1 ± iii ] 0.744 1109953 1 53.0901070 -27.7361164 21.64 6811 19.3 ± · · · · · · · · · ± α ± iii ] 0.281 1110494 1 53.1079712 -27.7337646 21.99 8406 80.3 ± α ± · · · · · · · · · ± iii ] 0.314 1111549 1 53.1024857 -27.7296772 22.12 8625 48.0 ± α ± iii ] 0.376 1112157 1 53.0659561 -27.7309017 24.45 9030 75.6 ± α ± · · · · · · · · · ± iii ] 0.567 3116191 1 53.1104584 -27.7176895 20.86 8008 63.9 ± · · · · · · · · · ± iii ] 0.683 2117138 1 53.0722466 -27.7189407 21.24 8213 31.0 ± · · · · · · · · · ± β ± iii ] 0.557 3117929 1 53.1232452 -27.7181969 22.12 6668 13.4 ± iii ] 0.340 1117929 2 53.1227493 -27.7181206 22.12 6675 42.3 ± iii ] 0.340 1117929 2 53.1227493 -27.7181206 22.12 8794 15.1 ± α ± α ± iii ] 0.342 1118091 1 53.1171913 -27.7188969 23.51 8807 12.7 ± α ± iii ] 0.646 2118138 1 53.1340027 -27.7167816 21.13 7970 17.7 ± · · · · · · · · · ± iii ] 0.628 3118673 1 53.0913582 -27.7176514 24.62 8670 26.4 ± · · · · · · · · · ‡ ± iii ] 0.734 2119341 1 53.0700302 -27.7166138 25.23 8222 4.8 ± β ± iii ] 0.691 3119489 † ± · · · · · · · · · ± · · · · · · · · · ± iii ] 0.605 3121127 1 53.0573578 -27.7133713 21.23 7588 15.8 ± iii ] 0.519 3121733 1 53.0399170 -27.7116451 23.49 6270 10.3 ± ii ] 0.683 1121733 1 53.0399170 -27.7116451 23.49 8404 30.6 ± iii ] 0.683 1121817 1 53.0965118 -27.7111111 24.60 8345 32.8 ± iii ] 0.671 3121821 1 53.0656967 -27.7118549 23.80 8017 20.6 ± · · · · · · · · · ± ii ] 0.997 1122206 1 53.0856705 -27.7113590 24.76 9975 · · · · · · [O iii ] 0.997 1122668 1 53.0660706 -27.7097225 23.07 6242 8.1 ± iii ] 0.251 1122668 1 53.0660706 -27.7097225 23.07 8211 13.5 ± α ± β ± iii ] 0.640 3123301 1 53.0775757 -27.7081566 22.56 7800 11.6 ± β ± iii ] 0.604 3123301 2 53.0772972 -27.7082272 22.56 8001 134.3 ± iii ] 0.602 3123448 † ± · · · · · · · · · ± β ± iii ] 0.418 1123859 1 53.0642700 -27.7057590 22.62 9338 17.7 ± α ± iii ] 0.418 1124708 1 53.0647736 -27.7055855 24.71 7075 22.6 ± · · · · · · · · · ± iii ] 0.427 1 TABLE 1 — Continued
PEARS Knot RA Dec i ′ AB Wavelength Flux EW Line Grism FlagID − erg/s/cm ) (˚A) ID Redshift (*)124761 1 53.0544395 -27.7015305 21.29 9400 · · · · · · H α ± ii ] 1.026 3125725 1 53.0384941 -27.6966705 19.88 8171 70.8 ± · · · · · · · · · ± ii ] 0.847 1126769 1 53.0761490 -27.7011623 23.04 9249 24.6 ± iii ] 0.847 1127697 1 53.0613823 -27.6981525 22.61 7040 8.5 ± iii ] 0.422 1127697 1 53.0613823 -27.6981525 22.61 9333 18.0 ± α † ± iii ] 0.233 1128312 † ± α ± β ± iii ] 0.457 1128538 2 53.0531197 -27.6958714 22.68 7092 55.7 ± iii ] 0.457 1128538 2 53.0531197 -27.6958714 22.68 9348 21.3 ± α ± β ± iii ] 0.603 3130264 1 53.0469208 -27.6908588 22.64 7681 17.0 ± · · · · · · · · · ± iii ] 0.851 2 NOTES: —No data indicates measurement was not possible. In the case of line IDs, no data indicates that no suitable line ID was found for thegiven input redshift. “Grism Redshift” column gives re–calculated redshift based on the line identification. “Flag” column gives source of inputredshift used for line identification, if needed: 1—two lines visible in spectrum, no prior redshift needed; 2—single line in spectrum, line ID andgrism redshift based on prior spectroscopic redshift; 3—single line in spectrum, line ID and grism redshift based on prior photometric redshift;4—single line in spectrum, line ID and grism redshift based on prior spectrophotometric redshift (see Section 3.3). Objects 68739–96627 are fromthe HUDF. † CDF-S X-ray sources. From Grogin et al. (2009, in preparation) matches to PEARS sources. ‡ CDF-S X-ray sources with L X & erg s − and thus likely AGN. From Grogin et al. (2009, in preparation). TABLE 2Summary of ELG Detections in South Fields
Field
NOTE: —Here knots with multiple lines means two lines sufficient to deduce a wavelength ratio and therefore secure grism redshift; i.e. not [O iii ]and H β since a set wavelength ratio was used in the fitting algorithm. TABLE 3Summary of Lines Detected in South Fields
Field iii ] H α [O ii ] H β C iv C iii ] MgII NeIII H γγ