Michael S. Wiggs

WFPC2 Observations of the Hubble Deep Field South

The Hubble Deep Field South (HDF-S) observations targeted a high Galactic latitude field near QSO J2233-606. We present Wide Field Planetary Camera 2 observations of the field in four wide bandpasses centered at roughly 300, 450, 606, and 814 nm. Observations, data reduction procedures, and noise properties of the final images are discussed in detail. A catalog of sources is presented, and the number counts and color distributions of the galaxies are compared with a new catalog of the original Hubble Deep Field (HDF-N) that has been constructed in an identical manner. The two fields are qualitatively similar, with the galaxy number counts for the two fields agreeing to within 20%. The HDF-S has more candidate Lyman break galaxies at z > 2 than the HDF-N. The star formation rate per unit volume computed from the HDF-S, based on the UV luminosity of high-redshift candidates, is a factor of 1.9 higher than from the HDF-N at z ~ 2.7, and a factor of 1.3 higher at z ~ 4.

The Hubble Deep Field South: Formulation of the Observing Campaign

Deep, multiband observations of high Galactic latitude fields are an essential tool for studying topics ranging from Galactic structure to extragalactic background radiation. The Hubble Deep Field (HDF-N) observations obtained in 1995 December established a standard for such narrow, deep surveys. The field has been extensively analyzed by a variety of groups and has been widely studied with imaging and spectroscopy over wavelengths ranging from 10-3 to 2 × 105 μm. We describe here a second deep field campaign (HDF-S), this time in the southern hemisphere, undertaken by the Hubble Space Telescope (HST) in 1998 October in a program very similar to the northern Hubble Deep Field. Imaging and spectroscopy of three adjacent fields in the southern continuous viewing zone were obtained simultaneously for 150 orbits, and a mosaic of flanking fields was imaged for 27 additional orbits. Two important features of the HDF-S distinguish it from the HDF-N: the campaign included parallel observations by the three main HST instruments—WFPC2, STIS, and NICMOS—and the HDF-S location was selected to place a bright z = 2.24 quasar in the STIS field of view. The HDF-S observations consist of WFPC2 images in filters close to U, B, V, and I, a deep STIS image of the field surrounding the quasar, spectroscopy of the quasar with STIS from 1150 to 3560 A, and deep imaging of an adjacent field with NICMOS camera 3 at 1.1, 1.6, and 2.2 μm. All of the HDF-S data were fully reduced and made publicly available within 2 months of the observations, and we describe here the selection of the fields and the observing strategy that was employed. Detailed descriptions of the data and the reduction techniques for each field, together with the corresponding source catalogs, appear in separate papers.

Tomographic separation of composite spectra. 2: The components of 29 UW Canis Majoris

We have analyzed the UV photospheric lines of 29 CMa, a 4.39 day period, double-lined O-type spectroscopic binary. Archival data from International Ultraviolet Explorer (IUE)(28 spectra well distributed in oribital phase) were analyzed with several techniques. We find that the mass ratio is q = 1.20 +/- 0.16 (secondary more massive) based on three independent arguments. A tomography algorithm was used to produce the separate spectra of the two stars in six UV spectral regions. The MK spectral classifications of the primary and secondary, O7.5-8 Iab and O9.7 Ib, respectively, were estimated through a comparison of UV line ratios with those in spectral standard stars. The flux ratio of the stars in the UV is 0.36 +/- 0.07 (primary brighter). The primary has a strong P Cygni NIV wavelength 1718 feature, indicating a strong stellar wind. We also present tomographic reconstructions of visual spectral data in the range 4300-4950 A, based on seven observations of differing orbital phases, which confirm the UV classifications, and show that the primary is an Of star. From the spectral classifications, we estimate the temperatures of the stars to be 33,750 K and 29,000 K for primary and secondary, respectively. We then fit visual and UV light curves and show that reasonably good fits can be obtained with these temperatures, a semicontact configuration, an inclination of 74 deg. +/- 2 deg., and an intensity ratio r is less than 0.5.

Tomographic Analysis of Hα Profiles in HDE 226868/Cygnus X-1

We present high-quality Hα spectra of the massive X-ray binary HDE 226868 = Cyg X-1 that were made in 1985 and 1986. We measured radial velocities using the He I λ6678 line, and we use the resulting orbital solution together with a Hipparcos light curve of the ellipsoidal variation to arrive at a revised period estimate of P = 5.59977 ± 0.00002 days. We analyze the orbital phase-related variations in Hα emission using a Doppler tomography algorithm, and we show that the profile variations are well matched by a linear combination of two components: a P Cygni profile that moves with the motion of the supergiant star and an emission component that follows an antiphase but phase-shifted velocity curve (semiamplitude Kem = 68 km s-1 and radial velocity maximum at 0 = 0.86; these parameters are similar to those for the He II λ4686 emission line). We use a vector decomposition of this motion to argue that the latter emission component forms between the stars in a focused wind flow from the supergiant to the unseen companion. We searched for but found no clear evidence of Hα emission from the accretion disk surrounding the companion (any such emission contributes less than 3% of the continuum intensity). The results demonstrate that the Hα line provides an important probe of the mass transfer process that eventually fuels the X-ray source.

Tomographic separation of composite spectra. The components of Plaskett's Star

The UV photospheric lines of Plasketts Star (HD 47129), a 14.4 day period, double lined O-type spectroscopic binary were analyzed. Archival data from IUE (17 spectra well distributed in orbital phase) were analyzed with several techniques. A cross correlation analysis, which showed that the secondary produces significant lines in the UV, indicates that the mass ratio is q = 1.18 {plus minus} 0.12 (secondary slightly more massive). A tomography algorithm was used to produce the separate spectra of the two stars in six spectral regions. The interpolated spectral classifications of the primary and secondary, 07.3 I and 06.2 I, respectively, were estimated through a comparison of UV line ratios with those in spectral standard stars. The intensity ratio of the stars in the UV is 0.53 {plus minus} 0.05 (primary brighter). The secondary lines appear rotationally broadened, and the projected rotational velocity V sin i for this star is estimated to be 310 {plus minus} 20 km/s. The possible evolutionary history of this system is discussed through a comparison of the positions of the components and evolutionary tracks in the H-R diagram.

Hα Spectroscopy of the Unusual Binary V Sagittae

?????We present high-quality spectra of the H? emission line of the nova-like variable V Sge, obtained during a photometric bright state during 1986 July. The profiles have several components, including (1) a very broad, flat-topped emission line that forms in the optically thin wind of one of the stars, (2) a central, narrow peak that probably originates in a circumbinary shell, and (3) a moving component that attains an extreme velocity of approach just prior to secondary eclipse (when the brighter and lower mass Roche lobe?filling primary star is in the foreground). We review models for the emission based on the expected collision of the stellar winds of both stars, and suggest that the moving component originates in a high-density region that extends from between the stars to above the leading hemisphere of the primary. The example of V Sge shows that interacting binaries may cease mass transfer in favor of mass ejection from the system at some stage in their evolution.

A spectroscopic search for colliding stellar winds in O-type close binary systems. III - 29 UW Canis Majoris

The orbital-phase variations in the optical emission lines and UV P Cygni lines of the massive O-type binary 29 UW Canis Majoris are investigated in a search for evidence of colliding winds. High SNR spectra of the H-alpha and He I 6678-A emission lines are presented, and radial velocity curves for several features associated with the photosphere of the more luminous primary star are given. The H-alpha features consists of a P Cygni component that shares the motion of the primary, and which probably originates at the base of its wind, and a broad, stationary emission component. It is proposed that the broad emission forms in a plane midway between the stars where the winds collide. A simple geometric model is used to show that this placement of the broad component can explain the lack of orbital velocity shifts, the near-constancy of the emission strength throughout the orbit, the large velocities associated with the H-alpha wings, and the constancy of the velocity range observed.

A spectroscopic search for colliding stellar winds in O-type close binary systems. II - Plaskett's star (HD 47129)

New evidence for colliding winds in the massive O-type binary system Plasketts star is reported. High S/N ratio spectra of the H-alpha and He I 6678 emission lines are presented, and their orbital phase-related variations are examined in order to derive the locations and motions of the high-density gas in the system. Radial velocity cures for several absorption and emission lines associated with the photosphere of the primary are also provided. The H-alpha emission profiles are complex, with very broad wings and a sharp spikelike feature that approximately follows the motion of the primary star. The radial velocity curve for this spike lags behind the photospheric velocity curve of the primary by 0.066 in phase. It is suggested that the high-velocity H-alpha emission is related to instabilities in the intershock region between the two component stars. The H-alpha phase-related variations are compared with those observed in the UV wind lines in IUE archival spectra.

A spectroscopic search for colliding stellar winds in O-type close binary systems. IV - Iota Orionis

We present Hα and He I λ6678 line profiles for the eccentric orbit binary ι Ori. We have applied a tomography algorithm which uses the established orbital velocity curves and intensity ratio to reconstruct the spectral line profiles for each star. The He I profiles appear as pure photospheric lines, and Hα shows variable emission in the line core throughout the orbit (which is typical of O giants) and in the blue wing near periastron passage. We show that the blue wing emission is consistent with an origin between the stars which probably results from a dramatic focusing of the primarys stellar wind at periastron

The Hubble Deep Field South Flanking Fields

As part of the Hubble Deep Field South program, a set of shorter two-orbit observations were obtained of the area adjacent to the deep fields. The WFPC2 flanking fields cover a contiguous solid angle of 48 arcmin2. Parallel observations with the STIS and NICMOS instruments produce a patchwork of additional fields with optical and near-infrared (1.6 μm) response. Deeper parallel exposures with WFPC2 and NICMOS were obtained when STIS observed the NICMOS deep field. These deeper fields are offset from the rest, and an extended low surface brightness object is visible in the deeper WFPC2 flanking field. In this data paper, which serves as an archival record of the project, we discuss the observations and data reduction and present SExtractor source catalogs and number counts derived from the data. Number counts are broadly consistent with previous surveys from both ground and space. Among other things, these flanking field observations are useful for defining slit masks for spectroscopic follow-up over a wider area around the deep fields, for studying large-scale structure that extends beyond the deep fields, for future supernova searches, and for number counts and morphological studies, but their ultimate utility will be defined by the astronomical community.