Aavso paper Session I sunday Sunday, May 22, 2011, 9: 30 am – 12: 00 pm
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328Surveys and Large ProgramsPoster SessionEssex Ballroom328.01
CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey Henry Closson Ferguson1, CANDELS collaboration 1STScI. 8:00 AM - 7:00 PM Essex Ballroom The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution, from redshift z ~ 8 to 1.5. It will image more than 250,000 distant galaxies using three separate cameras on board the Hubble Space Telescope, from the mid-UV to near-IR. It will also find and measure Type Ia SNe beyond z > 1.5 and test their accuracy as standard candles for cosmology. Five premier multi-wavelength sky regions are selected. Each has multi-wavelength data from Spitzer and other facilities, plus extensive spectroscopy of the brighter galaxies; additional ancillary data are still arriving. The use of five widely separated fields mitigates cosmic variance and yields statistically robust and complete samples of galaxies down to a stellar mass of a billion solar masses out to z ~ 2, and down to the knee of the UV luminosity function of galaxies out to z ~ 8. The survey covers approximately 800 square arcminutes and is divided into two parts. The CANDELS/Deep survey (5 σ point-source limit H_AB = 27.8 mag) covers ~ 125 square arcminutes within GOODS-N and GOODS-S. The CANDELS/Wide survey includes GOODS and three additional fields (EGS, COSMOS, and UDS) and covers the full area to 5 σ point-source limit of H_AB = 27.0 mag or better. Data from the survey are non-proprietary, and high-level science products are released within 3 months of each observation. 328.02
Tracing the Mass Assmebly at Large Radii of Massive Quiescent Galaxies Elizabeth J. McGrath1, D. Koo1, M. Mozena1, S. Faber1, A. van der Wel2, S. Wuyts3, A. Koekemoer4, CANDELS Collaboration 1University of California, Santa Cruz, 2MPIA, Germany, 3CfA, 4STScI. 8:00 AM - 7:00 PM Essex Ballroom Using high-resolution imaging data from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS), we examine the growth of spheroids from z~2.5 to the present. Evidence that massive quiescent galaxies undergo dramatic size evolution since z~2.5 has been steadily increasing. The compact sizes of high-redshift quiescent galaxies imply densities that are up to two orders of magnitude greater than galaxies in the local Universe of similar mass. However, it is unclear whether measurements to-date, many of which have relied on rest-frame near-UV imaging, have been underestimated due to effects such as signal-to-noise and age or metallicity gradients. Recently it has been suggested that these compact galaxies could survive as the cores of massive ellipticals in the local Universe, growing low-surface-brightness halos through dry mergers, thus preserving the central mass density while increasing the effective radii. The depth of CANDELS imaging at both rest-frame near-UV and optical wavelengths allows us to reliably measure sizes and color gradients of passive galaxies for the first time over a large region of the sky, enabling us to determine when early-type galaxies start to grow their halos and how they evolve onto the local size-mass relation. 328.03
8:00 AM - 7:00 PM Essex Ballroom Initial results are presented on searches for high-reshift AGN candidates using the new WFC3/IR data obtained as part of the CANDELS survey, including the GOODS, UDS and EGS fields. Obtaining constraints on the numbers of AGN at high redshifts is crucial for improving our understanding of their growth and evolution as well as their relationship to their host galaxies, especially important for the physical processes that underlie the M-sigma relation. Yet obtaining sufficiently large samples of z>6 AGN has proved elusive to date, due to their low surface density as well as their faint magnitudes. The new deep WFC3/IR imaging provided by the CANDELS survey offers the first opportunity to obtain sufficiently large samples of these sources to be able to constrain the evolution of the AGN luminosity function up to high redshift, with corresponding implications for the co-evolution of galaxies and their central supermassive black holes. 328.04
8:00 AM - 7:00 PM Essex Ballroom The CANDELS HST Multi-cycle Treasury Program completed its observations of the UKIDSS UDS field in January 2011. The coverage comprises WFC3/IR exposures in J and H across a contiguous ≈200 square arcminutes, and coordinated parallel ACS/WFC exposures in V and I across a contiguous ≈250 square arcminutes that largely overlaps the WFC3/IR coverage. These observations were split between two epochs with ≈52-day spacing for the primary purpose of high-z supernovae (SNe) detection and follow-up. However, this combination of sensitivity, high resolution, and time spacing is also well-suited to detect optical and near-infrared variability ("ONIV") among ≈10000 moderate-z galaxy nuclei (≈7500 in the near-infrared to AB∼24 mag; ≈7500 in the overlapping optical to AB∼25 mag) on rest-frame timescales of up to several weeks. The overwhelming majority of these variable galaxy nuclei will be AGN; the small fraction arising from SNe have already been meticulously culled by the CANDELS high-z SNe search effort. These ONIV galaxy nuclei potentially represent a significant addition to the census of distant AGN subject to multi-wavelength scrutiny with CANDELS. We present the preliminary results of our variability analysis, including a comparison of the HST ONIVs with the known AGN candidates in the field from deep Spitzer and XMM-Newton imaging across the field, and from extensive optical spectroscopy. We also assess the redshift distribution of the ONIVs from both spectroscopy and from robust SED-fitting incorporating ancillary deep ground-based imaging along with the CANDELS VIJH photometry. 328.05
A Comparison Of GOODS NICMOS Survey And CANDELS WFC3 H-band Galaxy Morphologies In The GOODS-South Field Ray A. Lucas1, N. A. Grogin1, C. J. Conselice2, A. Koekemoer1, A. Bauer3, CANDELS Collaboration, GOODS NICMOS-H Survey Collaboration 1STScI, 2University of Nottingham, United Kingdom, 3AAO, Australia. 8:00 AM - 7:00 PM Essex Ballroom The large amount of Hubble Space Telescope near-infrared imaging done in the GOODS-South field in both NICMOS and now WFC3 IR allows us to make a comparison and to some degree a calibration of how well one may assume the measurements made from data taken with one camera may be related to similar measurements of objects in earlier publications and/or other fields where data from only one camera are present. We are performing such a comparison on the H-band data from the GNS GOODS-South observations and the CANDELS WFC3 IR data on the same field. In all of these comparisons, despite some possible differences due to the detector resolution, efficiency, filter throughput, and resulting SExtractor catalogs, etc. for given objects, we will be comparing data on the same galaxies which were imaged with different cameras in the same basic bandpass, using standard quantitative morphological parameters. From this, one may be able to determine how well one can in general extrapolate measurements of objects made with one camera to those made with the other in various fields across the sky, and this may offer some guidance for interpretation of reliability of morphological results when reading older papers or measuring morphological parameters where only NICMOS data is available, for example. 328.06
8:00 AM - 7:00 PM Essex Ballroom Ultraluminous Infrared Galaxies (ULIRGs, L_IR>10^12 L⊙) in the local universe are all interacting and merging galaxies. To date, studies of ULIRGs at high redshift have found a variety of results due to their varying selection effects and small sample sizes. Here, we present the results of a morphological analysis of a sample of high redshift (z~1-3) ULIRGs. These galaxies are selected based on their infrared luminosities measured using 100 and 160 micron data from the GOODS-Herschel coverage of GOODS-S. We visually classified all of the ULIRGs as well as a comparison sample at the same redshift covering the same H band magnitude range using ACS and WFC3 data from the GOODS and CANDELS surveys. We compare our results to those from other classifiers as well as several automated classification methods. The high resolution and increased sensitivity of WFC3 over NICMOS for this large sample of objects allows us to investigate the role of galaxy mergers among high redshift ULIRGs consistently for the first time. 328.07
Clumps of z~2 Star-forming Galaxies Yicheng Guo1, M. Giavalisco1, P. Cassata1, CANDELS Collaboration 1University of Massachusetts, Amherst. 8:00 AM - 7:00 PM Essex Ballroom We study the properties of red clumps of star-forming galaxies at z~2. A sample of 15 galaxies with spectroscopic redshift is selected from the HUDF, where ultra--deep and high- resolution optical (HST/ACS) and near--IR (HST/WFC3 IR) images are available to resolve the internal structure of z~2 galaxies at the kpc scale. We generate rest-frame UV-optical color maps of these galaxies after carefully matching image PSFs. Clumps are identified through visual inspection on the (z-H) maps. We run SED-fitting using the seven-band BVizYJH HST photometry of each pixel and measure the spatial distributions of stellar population parameters, such as stellar mass, star-formation rate, age and obscuration. In order to understand the origin of sub-galactic structures, we study the distributions of these properties of the pixels that are part of clumps and compare them with those of the surrounding disks. Our results help answer two questions: (1) whether the clumps are the progenitor of bulges and (2) whether old stellar populations (with age of a few Gyr) exist in star-forming galaxies at z~2. 328.08
8:00 AM - 7:00 PM Essex Ballroom We study the bivariate size-luminosity distribution of z~4 and z~5 Lyman Break Galaxies (LBG) in the GOODS fields. Our sample was selected using the Lyman Break color selection criteria in order to select rest-frame UV-bright star forming galaxies. We selected around 1250 B-dropouts (z~4) and 370 V-dropouts (z~5) in both GOODS fields and the HUDF field, down to ACS F850LP magnitude z_{850} = 26.5 (GOODS ACS dataset) and z_{850}=28.0 (HUDF dataset). We model the size distribution as a lognormal distribution and the luminosity function in the Schechter function form, and connect them with a power law relation between the peak size $r_0$ and the absolute magnitude $M$, $r_0 = r*(M/M*)^{\beta}$. Galaxy magnitude and size are measured first with SExtractor, then we use GALFIT to fit a single Sersic component to derive the effective radius. We also performed a Monte Carlo simulation in order to account for the measurement bias and scatter of SExtractor and GALFIT. The result of the simulation is convolved with the size-luminosity distribution models to compare with the observed distributions. We will compare our best-fit distribution with the luminosity functions published in the literature at similar redshifts. 328.09
8:00 AM - 7:00 PM Essex Ballroom The SDSS-III Baryon Oscillation Spectrocopic Survey (BOSS) will measure redshifts for 1.4 million massive galaxies between 0.2 328.10
8:00 AM - 7:00 PM After eight months of continuous observations from a sun-synchronous polar orbit, WISE mapped the entire sky at 3.4um, 4.6um, 12um and 22um, producing a coadded Image Atlas and a Source Catalogue, available through the Infrared Science Archive. The data reduction pipeline was optimized to detect and measure the fluxes of point sources. Sources that are larger than one arc minute in diameter, however, will not have been characterized in the released data products. Accordingly, we have begun a dedicated project to fully characterize large, nearby galaxies and produce a legacy image atlas and catalogue that will serve the community for decades to come. Here we demonstrate the early results of the WISE Large Galaxy Atlas project for a dozen galaxies of diverse morphology, including M51, M83, and M101. Photometry and surface brightness decomposition is carried out with special super-resolution processing of WISE imaging, achieving spatial resolutions similar to that of Spitzer-IRAC. In addition to the super-resolution images, WISE's all-sky coverage provides a tremendous advantage over Spitzer for building a complete nearby catalog, tracing both stellar mass and star-formation histories. 328.11
8:00 AM - 7:00 PM We present the catalog from the first 70 months of the Swift-BAT all-sky hard X-ray survey. Over 1100 sources have been detected in the 15-200 keV band above the 4.8 sigma detection threshold, including over 500 AGN. We will show the breakdown of source types detected in the survey and present new spectra and lightcurves. 328.12
8:00 AM - 7:00 PM The Panoramic Survey Telescope And Rapid Response System-1 (Pan-STARRS-1, PS1) has been in full survey operation since May 2010. The Medium Deep Survey (MDS) component is allocated 25% of the time to cover 11 fields (~8 sq. deg. each) typically with significant multi-wavelength overlap from previous surveys (i.e., SDSS, DEEP2, CDFS, COSMOS). The g,r,i,z filters are covered every 3 days (the y filter during bright time) with a nightly depth to sample SNIa beyond redshifts of 0.5 (r,i~16--23.5 mag). To date, more than 1300 optical transient candidates have been discovered in the PS1-MDS, including more than 140 spectroscopically confirmed supernovae. We will present the initial, regular public release of stationary transient candidate events from the PS1-MDS and the future direction of these public releases as the survey continues. 328.13
8:00 AM - 7:00 PM In 1999, RECONS (Research Consortium on Nearby Stars) began gathering astrometric data using the CTIO 0.9m under the auspices of the NOAO Surveys Program. In 2003, SMARTS began operating the 0.9m and the program continued, with an enhanced ability to acquire long-term astrometric series on the nearest stars. With over a decade of milli-arcsecond astrometry for hundreds of red dwarfs within 25 pc, we now have a rich dataset in which to search for previously unknown stellar, substellar, and planetary companions. We can also use our data to better constrain the orbits of known binaries to reduce their mass errors to less than a few percent, and consequently test astrophysical models as never before. 328.14
8:00 AM - 7:00 PM The Advanced Spectral Library (ASTRAL) is a Hubble Space Telescope (HST) Cycle 18 (2010-2011) Large Treasury Project, whose aim is to collect high-quality ultraviolet echelle spectra of bright stars utilizing the high-performance Space Telescope Imaging Spectrograph (STIS). In Cycle 18, ASTRAL focuses on eight iconic late-type objects -- all well-known bright stars with vaguely unpronounceable names like Procyon and Betelgeuse -- and will devote 146 HST orbits for the purpose. The objective is to record each of the targets with broad uninterrupted UV coverage (1150-3100 Angstroms) at the highest signal-to-noise and highest spectral resolution achievable within the available spacecraft time, and given a variety of observing constraints. The broad ultraviolet coverage will be achieved by splicing together echellegrams taken in multiple FUV and NUV prime echelle settings of STIS. The observing strategy was designed to maximize S/N, ensure accurate wavelength scales, and preserve the radiometric level of the UV spectral energy distribution. This is a progress report on the observational status of ASTRAL. Up-to-date information can be found at the project website:http://casa.colorado.edu/~ayres/ASTRAL/. |