We present 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 36 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.
We present a UV to mid-infrared multi-wavelength catalog in the CANDELS/GOODS-S field, combining the newly obtained CANDELS HST/WFC3 F105W, F125W, and F160W data with existing public data. The catalog is based on source detection in the WFC3 F160W band. The F160W mosaic includes the data from CANDELS deep and wide observations as well as previous ERS and HUDF09 programs. The mosaic reaches a 5{sigma} limiting depth (within an aperture of radius 0.17") of 27.4, 28.2, and 29.7 AB for CANDELS wide, deep, and HUDF regions, respectively. The catalog contains 34930 sources with the representative 50% completeness reaching 25.9, 26.6, and 28.1 AB in the F160W band for the three regions. In addition to WFC3 bands, the catalog also includes data from UV (U band from both CTIO/MOSAIC and VLT/VIMOS), optical (HST/ACS F435W, F606W, F775W, F814W, and F850LP), and infrared (HST/WFC3 F098M, VLT/ISAAC Ks, VLT/HAWK-I Ks, and Spitzer/IRAC 3.6, 4.5, 5.8, 8.0{mu}m) observations. The catalog is validated via stellar colors, comparison with other published catalogs, zero-point offsets determined from the best-fit templates of the spectral energy distribution of spectroscopically observed objects, and the accuracy of photometric redshifts. The catalog is able to detect unreddened star-forming (passive) galaxies with stellar mass of 10^10^M_{sun}_ at a 50% completeness level to z~3.4 (2.8), 4.6 (3.2), and 7.0 (4.2) in the three regions. As an example of application, the catalog is used to select both star-forming and passive galaxies at z~2-4 via the Balmer break. It is also used to study the color-magnitude diagram of galaxies at 0<z<4.
These catalogs, prepared using the SExtractor package (Bertin & Arnouts 1996A&AS..117..393B), are based on the version v2.0 of the reduced, calibrated, stacked and mosaiced images acquired with HST and ACS as part of the GOODS ACS Treasury program and of the PANS program of search for Type Ia supernovae at high redshift. It supersedes the "Initial Results" version (Giavalisco et al. 2004ApJ...600L..93G, Cat. II/261) The catalogs are z-band based, that is, source detection has been made using the z-band images. A variety of photometric apertures defined during the detection process have then been used as "fixed apertures" in the i, v and b-band images to derive the multi-band photometry. The r2.0z catalog release is based on the v2.0 images, which have significantly longer total exposure times in the z850 bandpass, and somewhat longer exposure times in the i775 and V606 bands as well. The only significant difference in the catalogs, other than that of being based on deeper data, is that a small astrometric offset was applied to the declination of GOODS-North images (only), from a comparison with SDSS, 2MASS and VLA (Morrison et al. 2010, Cat. J/ApJS/188/178): Dec(v2.0)=Dec(v1.0)-0.320arcsec
This is the third installment of the Galactic O-Star Spectroscopic Survey (GOSSS), a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R~2500 digital observations selected from the Galactic O-Star Catalog. In this paper, we present 142 additional stellar systems with O stars from both hemispheres, bringing the total of O-type systems published within the project to 590. Among the new objects, there are 20 new O stars. We also identify 11 new double-lined spectroscopic binaries, 6 of which are of O+O type and 5 of O+B type, and an additional new tripled-lined spectroscopic binary of O+O+B type. We also revise some of the previous GOSSS classifications, present some egregious examples of stars erroneously classified as O-type in the past, introduce the use of luminosity class IV at spectral types O4-O5.5, and adapt the classification scheme to the work of Arias et al.
We present the results of the Gould's Belt Distances Survey of young star-forming regions toward the Orion Molecular Cloud Complex. We detected 36 young stellar objects (YSOs) with the Very Large Baseline Array, 27 of which have been observed in at least three epochs over the course of two years. At least half of these YSOs belong to multiple systems. We obtained parallax and proper motions toward these stars to study the structure and kinematics of the Complex. We measured a distance of 388+/-5pc toward the Orion Nebula Cluster, 428+/-10pc toward the southern portion L1641, 388+/-10pc toward NGC 2068, and roughly ~420pc toward NGC 2024. Finally, we observed a strong degree of plasma radio scattering toward {lambda} Ori.
We report on i-band snapshot observations of 157 Sloan Digital Sky Survey quasars at 4.0<z<5.4 using the Advanced Camera for Surveys on the Hubble Space Telescope (HST) to search for evidence of gravitational lensing of these sources.
We present a multi-wavelength analysis of Swift gamma-ray burst GRB 090727, for which optical emission was detected during the prompt {gamma}-ray emission by the 2m autonomous robotic Liverpool Telescope and subsequently monitored for a further two days with the Liverpool and Faulkes Telescopes. Within the context of the standard fireball model, we rule out a reverse shock origin for the early-time optical emission in GRB 090727 and instead conclude that the early-time optical flash likely corresponds to emission from an internal dissipation process. Putting GRB 090727 into a broader observational and theoretical context, we build a sample of 36 {gamma}-ray bursts (GRBs) with contemporaneous early-time optical and {gamma}-ray detections. From these GRBs, we extract a sub-sample of 18 GRBs, which show optical peaks during prompt {gamma}-ray emission, and perform detailed temporal and spectral analysis in {gamma}-ray, X-ray, and optical bands. We find that in most cases early-time optical emission shows sharp and steep behavior, and notice a rich diversity of spectral properties. Using a simple internal shock dissipation model, we show that the emission during prompt GRB phase can occur at very different frequencies via synchrotron radiation. Based on the results obtained from observations and simulation, we conclude that the standard external shock interpretation for early-time optical emission is disfavored in most cases due to sharp peaks ({Delta}t/t<1) and steep rise/decay indices, and that internal dissipation can explain the properties of GRBs with optical peaks during {gamma}-ray emission.
The mechanisms giving rise to diffuse radio emission in galaxy clusters and, in particular, their connection with cluster mergers are still being debated. We explore the internal dynamics of Abell 2254, which has been shown to host a very clumpy and irregular radio halo. Our analysis is mainly based on redshift data for 128 galaxies acquired at the Telescopio Nazionale Galileo. We combined galaxy velocities and positions to select 110 cluster galaxies and analyze its internal dynamics. We also used new (g', r', i') photometric data acquired at the Isaac Newton Telescope, and (V, i') photometric data available in the Subaru Archive. X-ray data from the XMM-Newton Science Archive were analyzed to study the hot gas component.
We report on our detailed characterization of Earth's second known temporary natural satellite, or minimoon, asteroid 2020CD3. An artificial origin can be ruled out based on its area-to-mass ratio and broadband photometry, which suggest that it is a silicate asteroid belonging to the S or V complex in asteroid taxonomy. The discovery of 2020CD3 allows for the first time a comparison between known minimoons and theoretical models of their expected physical and dynamical properties. The estimated diameter of 1.2_-0.2_^+0.4^m and geocentric capture approximately a decade after the first known minimoon, 2006RH120, are in agreement with theoretical predictions. The capture duration of 2020CD3 of at least 2.7yr is unexpectedly long compared to the simulation average, but it is in agreement with simulated minimoons that have close lunar encounters, providing additional support for the orbital models. 2020CD3's atypical rotation period, significantly longer than theoretical predictions, suggests that our understanding of meter-scale asteroids needs revision. More discoveries and a detailed characterization of the population can be expected with the forthcoming Vera C. Rubin Observatory Legacy Survey of Space and Time.
Isolated early-type galaxies are evolving in unusually poor environments for this morphological family, which is typical of cluster inhabitants. We investigate the mechanisms driving the evolution of these galaxies. Several studies indicate that interactions, accretions, and merging episodes leave their signature on the galaxy structure, from the nucleus down to the faint outskirts. We focus on revealing such signatures, if any, in a sample of isolated early-type galaxies, and we quantitatively revise their galaxy classification. We observed 20 (out of 104) isolated early-type galaxies, selected from the AMIGA catalog, with the 4KCCD camera at the Vatican Advanced Technology Telescope (VATT) in the Sloan Digital Sky Survey (SDSS) g and r bands. These are the deepest observations of a sample of isolated early-type galaxies so far: on average, the light profiles reach {mu}_g_~=28.11+/-0.70mag/arcsec^2^ and {mu}_r_~=27.36+/-0,68mag/arcsec^2^. The analysis was performed using the AIDA package, providing point spread function-corrected 2D surface photometry up to the galaxy outskirts. The package provides a model of the 2D galaxy light distribution, which after model subtraction enhances the fine and peculiar structures in the residual image of the galaxies. Our re-classification suggests that the sample is composed of bona fide early-type galaxies spanning from ellipticals to late-S0s galaxies. Most of the surface brightness profiles are best fitted with a bulge plus disc model, suggesting the presence of an underlying disc structure. The residuals obtained after the model subtraction show the nearly ubiquitous presence of fine structures, such as shells, stellar fans, rings, and tails. Shell systems are revealed in about 60% of these galaxies. Because interaction, accretion, and merging events are widely interpreted as the origin of the fans, ripples, shells and tails in galaxies, we suggest that most of these isolated early-type galaxies have experienced such events. Because they are isolated (after 2-3Gyr), these galaxies are the cleanest environment in which to study phenomena connected with events like these.
