Inge Heyer

The Hubble Deep Field: Observations, data reduction, and galaxy photometry

The Hubble Deep Field (HDF) is a Director’s Discretionary program on HST in Cycle 5 to image an undistinguished field at high Galactic latitude in four passbands as deeply as reasonably possible. These images provide the most detailed view to date of distant field galaxies and are likely to be important for a wide range of studies in galaxy evolution and cosmology. In order to optimize observing in the time available, a field in the northern continuous viewing zone was selected and images were taken for ten consecutive days, or approximately 150 orbits. Shorter 1-2 orbit images were obtained of the fields immediately adjacent to the primary HDF in order to facilitate spectroscopic follow-up by ground-based telescopes. The observations were made from 18 to 30 December 1995, and both raw and reduced data have been put in the public domain as a community service. We present a summary of the criteria for selecting the field, the rationale behind the filter selection and observing times in each band, and the strategies for planning the observations to maximize the exposure time while avoiding earth-scattered light. Data reduction procedures are outlined, and images of the combined frames in each band are presented. Objects detected in these images are listed in a catalog with their basic photometric parameters.

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.

Bar Evolution over the Last 8 Billion Years: A Constant Fraction of Strong Bars in the GEMS Survey

Original article can be found at: --http://www.journals.uchicago.edu/--Copyright The American Astronomical Society

Charge‐Transfer Efficiency of WFPC2

ABSTRACT Observations of ω Centauri have been used to characterize the charge‐transfer efficiency (CTE) of the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope. A set of formulae has been developed to correct aperture photometry for CTE loss with dependencies on the X‐ and Y‐positions, the background counts, the brightness of the star, and the time of the observation. The observations indicate that for very faint stars on a very faint background, the CTE loss from the top to the bottom of a chip has increased from about 3% shortly after the cooldown of WFPC2 (1994 April 23) to roughly 40% in 1999 February. In general, typical WFPC2 exposures are much longer than these short‐calibration images, resulting in higher background which significantly reduces the CTE loss and minimizes the CTE problem for most science exposures.

WFPC2 Observations of NGC 454: An Interacting Pair of Galaxies*

We present WFPC2 images in the F450W, F606W and F814W filters of the interacting pair of galaxies NGC 454. Our data indicate that the system is in the early stages of interaction. A population of young star-clusters has formed around the late component, and substantial amounts of gas have sunk into the center of the earlier component, where it has not yet produced significant visible star formation or nuclear activity. We have photometric evidence that the star-clusters have strong line emission, which indicate the presence of a substantial component of hot, massive stars which formed less than 5-10 Myrs ago.

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.

Evolution and Impact of Bars over the Last Nine Gyr: Early Results from GEMS

Bars drive the dynamical evolution of disk galaxies by redistributing mass and angular momentum, and they are ubiquitous in present-day spirals. Early studies of the Hubble Deep Field reported a dramatic decline in the rest-frame optical bar fraction f opt to below 5% at redshifts z > 0.7, implying that disks at these epochs are fundamentally different from present-day spirals. The GEMS bar project, based on ~ 10,000 galaxies with HST-based morphologies and accurate redshifts over the range 0.2–1.3, aims at constraining the evolution and impact of bars over the last 9 Gyr. We present early results indicating that f opt remains ~ constant with a lower limit of ~ 30% over z ~ 0.2–1.3, corresponding to lookback times of ~ 2.5–9 Gyr. The bars detected at z > 0.6 are primarily strong with ellipticities of 0.4–0.8. Remarkably, both the bar fraction and range of bar sizes observed at z > 0.6, appear to be comparable to the values measured in the local Universe for bars of corresponding strengths. Implications for bar evolution models are discussed.

Anisotropic winds from T Tauri stars

Line profiles of CO 137 IS 113, and H alpha, observed in a dozen T Tauri stars with the KENO 4m echelle spectrograph, provide probes of the density, spatial extent, and anisotropy of T Tauri winds.