Victoria G. Laidler

The Great Observatories Origins Deep Survey: Initial Results from Optical and Near-Infrared Imaging

This special issue of the Astrophysical Journal Letters is dedicated to presenting initial results from the Great Observatories Origins Deep Survey (GOODS) that are primarily, but not exclusively, based on multiband imaging data obtained with the Hubble Space Telescope and the Advanced Camera for Surveys (ACS). The survey covers roughly 320 arcmin2 in the ACS F435W, F606W, F814W, and F850LP bands, divided into two well-studied fields. Existing deep observations from the Chandra X-Ray Observatory and ground-based facilities are supplemented with new, deep imaging in the optical and near-infrared from the European Southern Observatory and from the Kitt Peak National Observatory. Deep observations with the Space Infrared Telescope Facility are scheduled. Reduced data from all facilities are being released worldwide within 3-6 months of acquisition. Together, this data set provides two deep reference fields for studies of distant normal and active galaxies, supernovae, and faint stars in our own Galaxy. This Letter serves to outline the survey strategy and describe the specific data that have been used in the accompanying letters, summarizing the reduction procedures and sensitivity limits.

The Second-Generation Guide Star Catalog: Description and Properties

The Guide Star Catalog II (GSC-II) is an all-sky database of objects derived from the uncompressed Digitized Sky Surveys that the Space Telescope Science Institute has created from the Palomar and UK Schmidt survey plates and made available to the community. Like its predecessor (GSC-I), the GSC-II was primarily created to provide guide star information and observation planning support for Hubble Space Telescope. This version, however, is already employed at some of the ground-based new-technology telescopes such as GEMINI, VLT, and TNG, and will also be used to provide support for the James Webb Space Telescope (JWST) and GAIA space missions as well as the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, one of the major ongoing scientific projects in China. Two catalogs have already been extracted from the GSC-II database and released to the astronomical community. A magnitude-limited (RF = 18.0) version, GSC2.2, was distributed soon after its production in 2001, while the GSC2.3 release has been available for general access since 2007. The GSC2.3 catalog described in this paper contains astrometry, photometry, and classification for 945,592,683 objects down to the magnitude limit of the plates. Positions are tied to the International Celestial Reference System; for stellar sources, the all-sky average absolute error per coordinate ranges from 02 to 028 depending on magnitude. When dealing with extended objects, astrometric errors are 20% worse in the case of galaxies and approximately a factor of 2 worse for blended images. Stellar photometry is determined to 0.13-0.22 mag as a function of magnitude and photographic passbands (RF , BJ , IN ). Outside of the galactic plane, stellar classification is reliable to at least 90% confidence for magnitudes brighter than RF = 19.5, and the catalog is complete to RF = 20.

Agn host galaxies at z ∼ 0.4-1.3 : Bulge-dominated and lacking merger-agn connection

We investigate morphological structure parameters and local environments of distant moderate-luminosity active galactic nucleus (AGN) host galaxies in the overlap between the HST/ACS observations of the Great Observatories Origins Deep Survey (GOODS) and the two Chandra Deep Fields. We compute near-neighbor counts and BViz asymmetry (A) and concentration (C) indices for ≈35,500 GOODS/ACS galaxies complete to , including z850 ≈ 26.6 the resolved hosts of 322 X-ray–selected AGNs. Distributions of (1) asymmetry for 130 AGN hosts z z 850 850 ! 23 and (2) near-neighbor counts for 173 AGN hosts are both consistent with non-AGN control samples. z850 ! 24 This implies no close connection between recent galaxy mergers and moderate-luminosity AGN activity out to appreciable look-back times ( ), approaching the epoch of peak AGN activity in the universe. The distri- z 1.3 bution of z850 C for the AGN hosts is offset by compared to the non-AGN, a 6.4 DC ≈ 0.5 j discrepancy much larger than can be explained by the possible influence of unresolved emission from the AGN or a circumnuclear starburst. The local universe association between AGN and bulge-dominated galaxies thus persists to substantial look-back time. We discuss implications in the context of the low-redshift supermassive central black hole mass correlation with host galaxy properties, including concentration.

TFIT: A Photometry Package Using Prior Information for Mixed‐Resolution Data Sets

ABSTRACT We describe the TFIT software package to measure galaxy photometry using prior information from high‐resolution observations. Our basic methodology is similar in principle but different in detail from previous procedures for crowded field photometry. We use the spatial positions and morphologies of objects in an image with higher angular resolution to construct object templates, which are then fitted to a lower resolution image, solving for the object fluxes as free parameters. Using extensive experiments on both simulated and real data, we show that this template‐fitting method measures accurate object photometry to the limiting sensitivity of the image. In this limit, our method derives robust flux upper limits for objects fainter than the limiting image surface brightness. We describe the challenges encountered in applying this technique to real data, and methods to cope with some of them.

Pandeia: a multi-mission exposure time calculator for JWST and WFIRST

Pandeia is the exposure time calculator (ETC) system developed for the James Webb Space Telescope (JWST) that will be used for creating JWST proposals. It includes a simulation-hybrid Python engine that calculates the two-dimensional pixel-by-pixel signal and noise properties of the JWST instruments. This allows for appropriate handling of realistic point spread functions, MULTIACCUM detector readouts, correlated detector readnoise, and multiple photometric and spectral extraction strategies. Pandeia includes support for all the JWST observing modes, including imaging, slitted/slitless spectroscopy, integral field spectroscopy, and coronagraphy. Its highly modular, data-driven design makes it easily adaptable to other observatories. An implementation for use with WFIRST is also available.

On the Nature of Type Ib Supernova Progenitors

The realization that there is a separate subclass of Type I supernovae (SNe) to be denoted as Type Ib came after the detailed study of the SN 1983N in M83 (PANAGIA et al [1]; see also PANAGIA [2], WHEELER and LEVREAULT [3], UOMOTO and KIRSHNER [4]). It was immediately clear that SN 1983N is distinctly different from the classical variety of Type I SNe (obviously denoted as Type Ia SNe) in a number of important aspects. Since then about a dozen SNe have been classified as Type Ib SNe, some newly discovered and others found just re-examining old spectra or paying due attention to the comments that the observers gave at the time when the original observations were made (e.g. BERTOLA [5]).

Type Ib supernovae: What they may be and what they are not

We show that the progenitors of Type Ib supernovae are likely to be moderately massive stars (M ∼ 7 M⊙) in binary systems and we argue that the hypothesis that they originate from very massive stars (M > 20 M⊙) is untenable both on an observational and a statistical basis.

The Selection of a Sampling Interval for Digitisation: How Fine is Fine Enough?

A critical property of digitized sky surveys prepared from photographic materials is the sample interval, δ, used by the microdensitometer. At issue is a tradeoff between coarse sample intervals that, while economical, do not allow the faithful reproduction of the information in photographic material, and fine intervals, which can record all of the information, but at a prohibitive cost. We investigate these issues by conducting Fourier analyses of images characteristic of the imaging process in the absence of noise and by examining the properties of object inventories for a test field digitized at a range of sampling intervals. Both analyses indicate that 15μm is an adequate sampling interval for modern Schmidt plates on Type III emulsions.