Gauging the dark matter fraction in a $L_*$ S0 galaxy at z=0.47 through gravitational lensing from deep HST/ACS imaging
G. Covone, M. Paolillo, N. R. Napolitano, M. Capaccioli, G. Longo, J. -P. Kneib, E. Jullo, J. Richard, O. Khovanskaya, M. Sazhin, N. A. Grogin, E. Schreier
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18 pages, 5 figures; accepted for publication in ApJ
We analyze a new gravitational lens, OAC-GL J1223-1239, serendipitously found in a deep I-band image of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). The lens is a L_*, edge-on S0 galaxy at z=0.4656. The gravitational arc has a radius of 0.42 arcsec. We have determined the total mass and the dark matter (DM) fraction within the Einstein radius as a function of the lensed source redshift, which is presently unknown. For z ~ 1.3, which is in the middle of the redshift range plausible for the source according to some external constraints, we find the central velocity dispersion to be ~180 km/s. With this value, close to that obtained by means of the Faber-Jackson relation at the lens redshift, we compute a 30% DM fraction within the Einstein radius (given the uncertainty in the source redshift, the allowed range for the DM fraction is 25-35 % in our lensing model). When compared with the galaxies in the local Universe, the lensing galaxy, OAC-GL J1223-1239 seems to fall in the transition regime between massive DM dominated galaxies and lower-mass, DM deficient systems.
This is the first paper of a series describing our measurement of weak lensing by large-scale structure using archival observations from the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). In this work we present results from a pilot study testing the capabilities of the ACS for cosmic shear measurements with early parallel observations and presenting a re-analysis of HST/ACS data from the GEMS survey and the GOODS observations of the Chandra Deep Field South (CDFS). We describe our new correction scheme for the time-dependent ACS PSF based on observations of stell…
With HST, colour-magnitude diagrams (CMDs) can be obtained for young star clusters well beyond the Local Group. Such data can help constrain cluster ages and metallicities, and also provide a reference against which intermediate- and high mass stellar models can be compared. Here, CMDs are presented for two massive (>10^5 Msun) clusters and compared with Padua and Geneva isochrones. The problem of the ratio of blue to red supergiants is also addressed.
Using HST/ACS images in four bands F435W, F606W, F775W and F850LP, we identify optical counterparts to the X-ray sources in the Chandra Deep Field South in the GOODS South field. A detailed study has been made of these sources to study their morphological types. We use methods like decomposition of galaxy luminosity profiles, color maps and visual inspection of 192 galaxies which are identified as possible optical counterparts of Chandra X-ray sources in the CDFS-GOODS field. We find that most moderate luminosity AGN hosts are bulge dominated in the redshift range (z \approx 0.4-1.3), but not …
We describe the details of the Hubble Space Telescope (HST) Advanced Camera for Surveys / Wide Field Channel (ACS/WFC) observations of the COSMOS field, including the data calibration and processing procedures. We obtained a total of 583 orbits of HST ACS/WFC imaging in the F814W filter, covering a field that is 1.64 square degrees in area, the largest contiguous field ever imaged with HST. The median exposure depth across the field is 2028 seconds (one HST orbit), achieving a limiting point-source depth AB(F814W) = 27.2 (5 sigma). We also present details about the astrometric image registrati…
We present the atlas of protoplanetary disks in the Orion Nebula based on the ACS/WFC images obtained for the HST Treasury Program on the Orion Nebula Cluster. The observations have been carried out in 5 photometric filters nearly equivalent to the standard B, V, Halpha, I, and z passbands. Our master catalog lists 178 externally ionized proto-planetary disks (proplyds), 28 disks seen only in absorption against the bright nebular background (silhouette disks), 8 disks seen only as dark lanes at the midplane of extended polar emission (bipolar nebulae or reflection nebulae) and 5 sources showin…
This paper reports on a survey of star clusters in M31 based on archival images from the Hubble Space Telescope. Paper I (Krienke and Hodge 2007) reported results from images obtained with the Wide Field/Planetary Camera 2 (WFPC2) and this paper reports results from the Advanced Camera for Surveys (ACS). The ACS survey has yielded a total of 339 star clusters. The color- integrated magnitude diagram of clusters shows three significant features: (1) a group of very red, luminous objects: the globular clusters, (2) a wide range in color for the fainter clusters, representing a considerable range…
We review the imaging and spectroscopic properties of the Lyman alpha emission in starburst galaxies. The Lyman alpha photons escape is largely driven by kinematical and orientation effects related to the presence of large scale expanding shells of neutral hydrogen. The various Lyman alpha profiles can be linked to the evolutionary state of the starburst. Our recent Lyman alpha imaging study using the HST-ACS is presented here: it highlights the presence of diffuse extended emission of low intensity leaking out the diffuse HI components. The similarities with the line profiles observed on high…
We present results from new deep HST/ACS photometry of I Zw 18, the most metal-poor blue compact dwarf galaxy in the nearby universe. It has been previously argued that this is a very young system that started forming stars only < 500 Myr ago, but other work has hinted that older (> 1 Gyr) red giant branch (RGB) stars may exist in this galaxy. Our deeper data indeed reveal evidence for an RGB. Underlying old (> 1 Gyr) populations are therefore present in even the most metal-poor systems, implying that star formation started at z > 0.1. The RGB tip (TRGB) magnitude and the properties of Cepheid…
We report the first results from an imaging program with the ACS camera on HST designed to measure the structural characteristics of a wide range of globular clusters in NGC 5128, the nearest giant elliptical galaxy. From 12 ACS/WFC fields, we have measured a total of 62 previously known globular clusters and have discovered 69 new high-probability cluster candidates not found in any previous work. We present magnitudes and color indices for all of these, along with rough measurements of their effective diameters and ellipticities. The luminosity distribution of this nearly-uncontaminated samp…
In this paper we analyse very short arcs of minor bodies of the Solar System detected on Hubble Space Telescope (HST) Wide Field Channel ACS images. In particular, we address how to constrain the Keplerian orbital elements for minor body detections, illustrating the method for 2 objects. One of the minor bodies left 13 successive trails, making it the most well-sampled object yet identified in the HST archive. Most interestingly, we also address the problem of ephemeris prediction and show that in the particular case of HST very short arcs the confinement window for subsequent recovery is sign…
We report the discovery of a rich population of low mass stars in the young, massive star forming region N66/NGC346 in the Small Magellanic Cloud, from deep V, I and H alpha images taken with the HST/ACS. These stars have likely formed together with the NGC346 cluster, ~3-5 Myr ago. Their magnitude and colors are those of pre-main sequence stars in the mass range 0.6-3 Mo, mostly concentrated in the main cluster, but with secondary subclusters spread over a region across ~45 pc. These subclusters appear to be spatially coincident with previously known knots of molecular gas identified in groun…
We present the first results from the HST/ACS Grism Parallel Survey, a large program obtaining deep, slitless ACS grism spectroscopy of high-latitude HST parallel fields. We report on 11 high Galactic latitude fields here, each with grism integration times >12 ks. We identify 601 compact emission line galaxies at z < 1.6, reaching emission lines to a flux limit of > 5 E-18 ergs/cm^2/s (3 sigma). We determine redshifts by cross correlation of the target spectra with template spectra, followed by visual inspection. We measure star formation rates from the observed [OII] 3727, [OIII] 5007 and Hal…
We study the possible contribution of optical galaxies detected with the {\it Hubble} ACS instrument to the near-IR cosmic infrared (CIB) fluctuations in deep {\it Spitzer} images. The {\it Spitzer} data used in this analysis are obtained in the course of the GOODS project from which we select four independent $10^\prime\times10^\prime$ regions observed at both 3.6 and 4.5 \um. ACS source catalogs for all of these areas are used to construct maps containing only their emissions in the ACS $B, V, i, z$-bands. We find that deep Spitzer data exhibit CIB fluctuations remaining after removal of for…
We exploit the superb resolution of the new HST/ACS mosaic image of M51 to select a large sample of young (< 1 Gyr) star clusters in the spiral disk, based on their sizes. The image covers the entire spiral disk in B, V, I and H_alpha, at a resolution of 2 pc per pixel. The surface density distribution of 4357 resolved clusters shows that the clusters are more correlated with clouds than with stars, and we find a hint of enhanced cluster formation at the corotation radius. The radius distribution of a sample of 769 clusters with more accurate radii suggests that young star clusters have a pref…
We have used the Advanced Camera for Surveys on board the Hubble Space Telescope to obtain deep photometry of the NGC 300 spiral galaxy in the Sculptor group. The results have been used to derive an accurate distance determination based on the Tip of the Red Giant Branch distance estimator. Both edge-detection and maximum likelihood methods have been applied, to derive a distance modulus (m-M)_0=26.30 +/- 0.03 +/- 0.12 for edge-detection, and (m-M)_0=26.36 +/- 0.02 +/- 0.12 for maximum likelihood. These results are fully consistent with the recent distance estimate derived from near-IR photome…
We present the first results of a large ACS Survey of Galactic globular clusters. This Hubble Space Telescope (HST) Treasury project is designed to obtain photometry with S/N > ~10 for main sequence stars with masses > ~0.2Msun in a sample of globulars using the Advanced Camera for Surveys (ACS) Wide Field Channel. Here we focus on clusters without previous HST imaging data. These include NGC 5466, 6779, 5053, 6144, Palomar 2, E 3, Lynga 7, Palomar 1, and NGC 6366. Our CMDs extend reliably from the horizontal branch to as much as seven magnitudes fainter than the main sequence turnoff and repr…
We have obtained deep color-magnitude diagrams of the Sagittarius dwarf irregular galaxy with the HST/ACS. The new diagrams unveil for the first time the star formation history of SagDIG. We identify a small population of red horizontal branch stars, which sets the first epoch of star formation in SagDIG back to ~9-10 Gyr ago. This shows that SagDIG has been able to maintain a very low mean metallicity (-2.2<[Fe/H]<-1.9) over a 10 Gyr life time, and most importantly, that all Local Group dwarf galaxies share an ancient (~10 Gyr) initial episode of star formation. Thus, at the moment, IZw18 rem…
Recent observations of globular clusters (GCs) in intermediate-age (2-4 Gyr old), early-type merger remnants have provided the hitherto `missing link' between young merger remnants and `normal' elliptical galaxies in the form of a GC subsystem with colors and luminosities consistent with population synthesis model predictions for those ages and ~solar metallicity. Here we present new, deep observations of the GC system of the intermediate-age merger remnant NGC 1316, using the ACS camera aboard Hubble Space Telescope, which allowed us to create luminosity functions (LFs) as a function of galac…
We present three-epoch multiband ($V_{606}$, $i_{775}$, $z_{850}$) measurements of galaxy shapes using the ``polar shapelet'' or Laguerre-expansions method with the Hubble Space Telescope ($HST$) Advanced Camera for Surveys (ACS) data, obtained as part of the {\it Great Observatories Origin Deep Survey} (GOODS). We take advantage of the unique features of the GOODS/ACS Fields to test the reliability of this relatively new method of galaxy shape measurement for weak lensing analysis and to quantify the impact of the ACS Point Spread Function (PSF) on $HST$/ACS data. We estimate the bias introdu…
We present new V and I-band HST/ACS photometry of I Zw 18, the most metal-poor blue compact dwarf (BCD) galaxy in the nearby universe. It has been argued in the past that I Zw 18 is a very young system that started forming stars only < 500 Myr ago, but other work has hinted that older (> 1 Gyr) red giant branch (RGB) stars may also exist. Our new data, once combined with archival HST/ACS data, provide a deep and uncontaminated optical color-magnitude diagram (CMD) that now strongly indicates an RGB. The RGB tip (TRGB) magnitude yields a distance modulus (m-M)_0 = 31.30 +/- 0.17, i.e., D = 18.2…
We derive the pre-shock density and scale length along the line of sight for the collisionless shock from a deep HST image that resolves the H alpha filament in SN1006 and updated model calculations. The very deep ACS high-resolution image of the Balmer line filament in the northwest (NW) quadrant shows that 0.25 < n_0 < le$ 0.4 cm-3 and that the scale along the line of sight is about 2 x 10^{18} cm, while bright features within the filament correspond to ripples with radii of curvature less than 1/10 that size. The derived densities are within the broad range of earlier density estimates, and…
AIM:Learn more about the origin of shells and dust in early type galaxies. METHOD: V-I colours of shells and underlying galaxies are derived, using HST Advanced Camera for Surveys (ACS) data. A galaxy model is made locally in wedges and subtracted to determine shell profiles and colours. We applied Voronoi binning to our data to get smoothed colour maps of the galaxies. Comparison with N-body simulations from the literature gives more insight to the origin of the shell features. Shell positions and dust characteristics are inferred from model galaxy subtracted images. RESULT: The ACS images re…
We obtained optical imaging polarimetry with the ACS/HRC aboard the HST of the 9 closest radio-galaxies in the 3C catalogue with an FR I morphology. The nuclear sources seen in direct HST images in these galaxies are found to be highly polarized with levels in the range ~2-11 % with a median value of 7 %. We discuss the different mechanisms that produce polarized emission and conclude that the only viable interpretation is a synchrotron origin for the optical nuclei. This idea is strengthened by the analogy with the polarization properties of BL Lac objects, providing also further support to t…
We present results of a morphological analysis of a small subset of the Spitzer Wide-area InfraRed Extragalactic survey (SWIRE) galaxy population. The analysis is based on public ACS data taken inside the SWIRE N1 field, which are the deepest optical high-resolution imaging available within the SWIRE fields as of today. Our reference sample includes 156 galaxies detected by both ACS and SWIRE. Among the various galaxy morphologies, we disentangle two main classes, spheroids (or bulge-dominated galaxies) and disk-dominated ones, for which we compute the number counts as a function of flux. We t…
ESO338-IG04 is a well known, local, luminous Blue Compact Galaxy. It has a complex morphology and contains a central young starburst with compact young star clusters. The galaxy was imaged using HST/ACS in the Lyman alpha line and continuum. Using the Starburst99 synthetic spectra and other imaging data from HST/WFPC2 we developed a technique that allows us to make the first photometrically valid continuum subtraction for the LYa line. Our results are in qualitative agreement with the models of LYa escape being regulated by kinematical properties of the interstellar medium. The line-only image…
We present a photometric analysis of the star clusters Lindsay 1, Kron 3, NGC339, NGC416, Lindsay 38, and NGC419 in the Small Magellanic Cloud (SMC), observed with the Hubble Space Telescope Advanced Camera for Surveys (ACS) in the F555W and F814W filters. Our color magnitude diagrams (CMDs) extend ~3.5 mag deeper than the main-sequence turnoff points, deeper than any previous data. Cluster ages were derived using three different isochrone models: Padova, Teramo, and Dartmouth, which are all available in the ACS photometric system. Fitting observed ridgelines for each cluster, we provide a hom…
We present ACS/HST coronagraphic observations of HD 100546, a B9.5 star, 103 pc away from the sun, taken in the F435W, F606W, and F814W bands. Scattered light is detected up to 14'' from the star. The observations are consistent with the presence of an extended flattened nebula with the same inclination as the inner disk. The well-known ``spiral arms'' are clearly observed and they trail the rotating disk material. Weaker arms never before reported are also seen. The inter-arm space becomes brighter, but the structures become more neutral in color at longer wavelengths, which is not consistent…
We report the discovery of an optical counterpart to a quiescent neutron star in the globular cluster Omega Centauri (NGC 5139). The star was found as part of our wide-field imaging study of Omega Cen using the Advanced Camera for Surveys (ACS) on Hubble Space Telescope. Its magnitude and color (R_625 = 25.2, B_435 - R_625 = 1.5) place it more than 1.5 magnitudes to the blue side of the main sequence. Through an H-alpha filter it is ~ 1.3 magnitudes brighter than cluster stars of comparable M_625 magnitude. The blue color and H-alpha excess suggest the presence of an accretion disk, implying t…
Hubble Space Telescope Advanced Camera for Surveys images of the young binary GG Tauri and its circumbinary disk in V and I bandpasses were obtained in 2002 and are the most detailed of this system to date. The confirm features previously seen in the disk including: a "gap" apparently caused by shadowing from circumstellar material; an asymmetrical distribution of light about the line of sight on the near edge of the disk; enhanced brightness along the near edge of the disk due to forward scattering; and a compact reflection nebula near the secondary star. New features are seen in the ACS imag…
We present stellar proper motions in the Galactic bulge from the Sagittarius Window Eclipsing Extrasolar Search (SWEEPS) project using ACS/WFC on HST. Proper motions are extracted for more than 180,000 objects, with >81,000 measured to accuracy better than 0.3 mas/yr in both coordinates. We report several results based on these measurements: 1. Kinematic separation of bulge from disk allows a sample of >15,000 bulge objects to be extracted based on >6-sigma detections of proper motion, with <0.2% contamination from the disk. This includes the first detection of a candidate bulge Blue Straggler…
We present a weak lensing analysis of one of the most distant massive galaxy cluster known, RDCS 1252.9-2927 at z=1.24, using deep images from the Advanced Camera for Survey (ACS) on board the Hubble Space Telescope (HST). By taking advantage of the depth and of the angular resolution of the ACS images, we detect for the first time at z>1 a clear weak lensing signal in both the i (F775W) and z (F850LP) filters. We measure a 5-σsignal in the i band and a 3-σsignal in the shallower z band image. The two radial mass profiles are found to be in very good agreement with each other, and provide a me…
We measure the surface density of i'-band dropout galaxies at z~6 through wide field HST/ACS imaging and ultra-deep Keck/DEIMOS spectroscopy. Using deep HST/ACS SDSS-i' (F775W) and SDSS-z' (F850LP) imaging from GOODS-N (200 arcmin^2), we identify 9 i'-drops satisfying an (i'-z')_AB>1.5 selection criterion to a depth of z'_AB=25.6 (corresponding to L*_UV at z~3-4). We use HK' imaging data to improve the fidelity of our sample, discriminating against lower redshift red galaxies and cool Galactic stars. Three i'-drops are consistent with M/L/T dwarf stars. We present ultra-deep Keck/DEIMOS spectr…
We describe the HST ACS Coma cluster Treasury survey, a deep two-passband imaging survey of one of the nearest rich clusters of galaxies, the Coma cluster (Abell 1656). The survey was designed to cover an area of 740 square arcmin in regions of different density of both galaxies and intergalactic medium within the cluster. The ACS failure of January 27th 2007 leaves the survey 28% complete, with 21 ACS pointings (230 square arcmin) complete, and partial data for a further 4 pointings (44 square arcmin). Predicted survey depth for 10 sigma detections for optimal photometry of point sources is g…
Multicolor coronagraphic images of the circumstellar disk around HD141569A have been obtained with the Hubble Space Telescope (HST) Advanced Camera for Surveys. B, V, and I images show that the disk's previously-described multiple-ring structure is actually a continuous distribution of dust with a tightly-wound spiral structure. Two, more open spiral arms extend from the disk, one of which appears to reach the nearby binary star HD141569BC. Diffuse dust is seen up to 1200AU from HD141569A. Although planets may exist in the inner region of the disk, tidal interaction with HD141569BC seems more …
We investigate the old globular cluster (GC) population of 68 faint (Mv>-16 mag) dwarf galaxies located in the halo regions of nearby (<12 Mpc) loose galaxy groups and in the field environment based on archival HST/ACS images in F606W and F814W filters. The combined color distribution of 175 GC candidates peaks at (V-I)=0.96 +/- 0.07 mag and the GC luminosity function turnover for the entire sample is found at Mv,to = -7.6 +/- 0.11 mag, similar to the old metal-poor LMC GC population. Our data reveal a tentative trend of Mv,to becoming fainter from late-type to early-type galaxies. The luminos…
We present the results obtained from an objective search for stellar clusters, both in the currently active nuclear starburst region, and in the post-starburst disk of M82. Images obtained with the HST/ACS in F435W(B), F555W(V), and F814W(I) filters were used in the search for the clusters. We detected 653 clusters of which 393 are located outside the central 450 pc in the post-starburst disk of M82. The luminosity function of the detected clusters show an apparent turnover at B=22 mag (M_B=-5.8), which we interpret from Monte Carlo simulations as due to incompleteness in the detection of fain…
We present photometry with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) of stars in the Magellanic starburst galaxy NGC 4449. The galaxy has been imaged in the F435W (B), F555W (V) and F814W (I) broad-band filters, and in the F658N (Halpha) narrow-band filter. Our photometry includes ~300,000 objects in the (B, V) color-magnitude diagram (CMD) down to V < 28, and ~400,000 objects in the (V, I) CMD, down to I < 27 . A subsample of ~200,000 stars has been photometrized in all the three bands simultaneously. The features observed in the CMDs imply a variety of stellar…
[ABRIDGED] We are undertaking an imaging study of local star-forming galaxies in the Lyman-alpha (Lya) emission line using the Solar Blind Channel (SBC) of the ACS onboard the HST. Observations have been obtained in Lya and H-alpha (Ha) and 6 continuum filters between ~1500AA and the I-band. Previously (Hayes et al 2005) we demonstrated that the production of Lya line-only images in the SBC-only data-set is non-trivial and that supporting data is a requirement. We here develop various methods of continuum subtraction and assess their relative performance using a variety of spectral energy dist…
We present the photometric calibration of the HST Advanced Camera for Surveys (ACS). We give here an overview of the performance and calibration of the 2 CCD cameras, the Wide Field Channel (WFC) and the High Resolution Channel (HRC), and a description of the best techniques for reducing ACS CCD data. On-orbit observations of spectrophotometric standard stars have been used to revise the pre-launch estimate of the instrument response curves to best match predicted and observed count rates. Synthetic photometry has been used to determine zeropoints for all filters in 3 magnitude systems and to …
A search for variable stars is performed using two epochs of Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging data for a 9.28 square arcminute portion of M31. This data set reveals 254 sources that vary by at least 4-sigma between epochs. The positions and 2-epoch B-band (equivalent) photometry of these sources are presented. The photometry suggests that this catalog includes most of the RR Lyrae population of this portion of M31.
We present Hubble Space Telescope/Advanced Camera for Surveys (ACS) weak-lensing and Chandra X-ray analyses of MS 1054-0321 at z=0.83, the most distant and X-ray luminous cluster in the Einstein Extended Medium-Sensitivity Survey (EMSS). The high-resolution mass reconstruction through ACS weak-lensing reveals the complicated dark matter substructure in unprecedented detail, characterized by the three dominant mass clumps with the four or more minor satellite groups within the current ACS field. The direct comparison of the mass map with the Chandra X-ray image shows that the eastern weak-lensi…
We determine the age, metallicity and initial mass function of three clusters, namely NGC 265, K~29, NGC 290, located in the main body of the Small Magellanic Cloud. In addition, we derive the history of star formation in the companion fields. We make use of ACS/WFC HST archive data. For the clusters, the age and metallicity are derived fitting the integrated luminosity function with single synthetic stellar population by means of the $χ^2$ minimization. For the companion fields, the history of star formation is derived using the $χ^2$ minimization together with the downhill-simplex method.For…
We use the ACS BViz data from the HUDF and all other deep HST ACS fields (including the GOODS fields) to find large samples of star-forming galaxies at z~4 and z~5 and to extend our previous z~6 sample. These samples contain 4671, 1416, and 627 B, V, and i dropouts, respectively, and reach to extremely low luminosities (0.01-0.04 L* or M(UV)~-16 to -17), allowing us to determine the rest-frame UV luminosity function (LF) and faint-end slope alpha at z~4-6 to high accuracy. We find faint-end slopes alpha of -1.73+/-0.05 at z~4, -1.66+/-0.09 at z~5, and -1.74+/-0.16 at z~6 -- suggesting that the…
The ACIS instrument on board the Chandra X-ray Observatory has been used to carry out the first systematic study of low-mass X-ray binaries (LMXBs) in M87. We identify 174 X-ray point-sources, of which ~150 are likely LMXBs. This LMXB catalog is combined with deep F475W and F850LP images taken with ACS on HST to examine the connection between LMXBs and globular clusters in M87. Of the 1688 globular clusters in our catalog, f_X = 3.6 +- 0.5% contain a LMXB and we find that the metal-rich clusters are 3 +- 1 times more likely to harbor a LMXB than their metal-poor counterparts. In agreement with…
(Abridged). We present new high spatial resolution narrowband imaging observations of extraplanar diffuse ionized gas (eDIG) in four late-type, actively star forming edge-on spirals, obtained with ACS on-board HST. Our F658N (H-alpha) observations reveal a multitude of structures on both small and large scales. Whereas all four galaxies have been studied with ground-based telescopes before, here the small scale structure of the extended emission line gas is presented for the first time at a spatial resolution of 0.05", corresponding to 5.0 pc at the mean distance to the target galaxies. The eD…
(Abridged) We study the internal color properties of a morphologically selected sample of spheroidal galaxies taken from HST/ACS ERO program of UGC 10214 (``The Tadpole''). By taking advantage of the unprecedented high resolution of the ACS in this very deep dataset we are able to characterize spheroids at sub-arcseconds scales. Using the V_606W and I_814W bands, we construct V-I color maps and extract color gradients for a sample of spheroids at I_814W < 24 mag. We investigate the existence of a population of morphologically classified spheroids which show extreme variation in their internal …
(Abridged) Luminous Compact Galaxies (LCGs) (M_B < -20, R_{1/2} < 4.5kpc and EW_{0}(OII) >15Å) constitute one of the most rapidly evolving galaxy populations over the last ~8 Gyr history of the universe. Due to their inherently compact sizes, any detailed quantitative analysis of their morphologies has proved to be difficult in the past. In this work we use the high angular resolution imaging data, from the HST/ACS GOODS survey, to study the quantitative morphology of a complete sample of LCGs in the redshift range 0.5 < z < 1.2. We have derived structural parameters for a representative sampl…
We present the results of a coronagraphic scattered-light imaging survey of six young disk candidate stars using the Hubble Space Telescope Advanced Camera for Surveys. The observations made use of the 1.8" occulting spot through the F606W (broad V) filter. Circumstellar material was imaged around HD 97048, a Herbig Ae/Be star located in the Chamaeleon I dark cloud at a distance of 180 pc. The material is seen between ~2" (360 AU) and ~4" (720 AU) from the star in all directions. A V-band azimuthally-averaged radial surface brightness profile peaks at r = 2" with a value of 19.6 +/- 0.2 mag ar…
We present the largest and most detailed survey to date of the stellar populations in the outskirts of M31 based on the analysis of 14 deep HST/ACS pointings spanning the range 11.5-45.0 kpc. We conduct a quantitative comparison of the resolved stellar populations in these fields and identify several striking trends. The color-magnitude diagrams (CMDs), which reach ~3 magnitudes below the red clump, can be classified into two main categories based on their morphologies. `Stream-like' fields, so named for their similarity to the CMD of the giant stellar stream, are characterized by a red clump …
The stars that end their lives as supernovae (SNe) have been directly observed in only a handful of cases, due mainly to the extreme difficulty in identifying them in images obtained prior to the SN explosions. Here we report the identification of the progenitor for the recent Type II-plateau (core-collapse) SN 2005cs in pre-explosion archival images of the Whirlpool Galaxy (M51) obtained with the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). From high-quality ground-based images of the SN from the Canada-France-Hawaii Telescope, we precisely determine the position of the SN …
As first Paper of a series devoted to study the old stellar population in clusters and fields in the Small Magellanic Cloud, we present deep observations of NGC121 in the F555W and F814W filters, obtained with the Advanced Camera for Surveys on the Hubble Space Telescope. The resulting color-magnitude diagram reaches ~3.5 mag below the main-sequence turn-off; deeper than any previous data. We derive the age of NGC121 using both absolute and relative age-dating methods. Fitting isochrones in the ACS photometric system to the observed ridge line of NGC121, gives ages of 11.8 +- 0.5 Gyr (Teramo),…
We measure F814W Surface Brightness Fluctuations (SBFs) for a sample of distant shell galaxies observed with the Advanced Camera for Survey (ACS) on board of HST. To evaluate the distance at galaxies, theoretical SBF magnitudes for the ACS@HST filters are computed for single burst stellar populations covering a wide range of ages (t=1.5-14 Gyr) and metallicities (Z=0.008-0.04). Using these stellar population models we provide the first M_SBF,F814W versus (F475W-F814W)0 calibration. The results suggest that optical SBFs can be measured at d>100 Mpc using high resolution spatial optical data.
We present discoveries of SNe Ia at z > 1 and the photometric diagnostic used to discriminate them from other types of SNe detected during the GOODS Hubble Space Telescope Treasury program with the Advanced Camera for Surveys (ACS). Photometric redshift measurements of the hosts combined with deep f606w, f775w, and f850lp imaging discriminates hydrogen-rich SNe II from SNe I at z > 1 by exploiting the ultraviolet (UV) deficit in the energy distributions of SNe Ia. This sorting allows rapid follow-up of space-based discoveries. Subsequent spectroscopy of 11 GOODS SNe Ia obtained from the ground…
In March 2006, the Hubble Heritage Team obtained a large four-filter (B, V, I, and H-alpha) six-point mosaic dataset of the prototypical starburst galaxy NGC 3034 (M82), with the Advanced Camera for Surveys (ACS) onboard the Hubble Space Telescope (HST). The resulting color composite Heritage image was released in April 2006, to celebrate Hubble's 16th anniversary. Cycle 15 HST proposers were encouraged to submit General Observer and Archival Research proposals to complement or analyze this unique dataset. Since our M82 mosaics represent a significant investment of expert processing beyond the…
A detailed imaging analysis of the globular cluster (GC) system of the Sombrero galaxy (NGC 4594) has been accomplished using a six-image mosaic from the Hubble Space Telescope Advanced Camera for Surveys. The quality of the data is such that contamination by foreground stars and background galaxies is negligible for all but the faintest 5% of the GC luminosity function (GCLF). This enables the study of an effectively pure sample of 659 GCs until ~2 mags fainter than the turnover magnitude, which occurs at M_V=-7.60+/-0.06 for an assumed m-M=29.77. Two GC metallicity subpopulations are easily …
(ABRIDGED) The ACS camera on board the Hubble Space Telescope has been used to obtain deep images of the giant elliptical galaxy NGC 3610, a well-established dissipative galaxy merger remnant. These observations supersede previous WFPC2 images which revealed the presence of a population of metal-rich globular clusters (GCs) of intermediate age (~1.5-4 Gyr). We detect a total of 580 GC candidates, 46% more than from the previous WFPC2 images. The new photometry strengthens the significance of the previously found bimodality of the color distribution of GCs. Peak colors in V-I are 0.93 +/-0.01 a…
We report the discovery of a strongly lensed arc system around a field elliptical galaxy in Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) images of a parallel field observed during NICMOS observations of the HST Ultra-Deep Field. The ACS parallel data comprise deep imaging in the F435W, F606W, F775W, and F850LP bandpasses. The main arc is at a radius of 1.6 arcsec from the galaxy center and subtends about 120 deg. Spectroscopic follow-up at Magellan Observatory yields a redshift z=0.6174 for the lensing galaxy, and we photometrically estimate z_phot = 2.4\pm0.3 for the arc. We…
In HST Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in the Magellanic Clouds centered on background quasars. We used these data to determine the proper motions of the LMC and SMC to better than 5% and 15% respectively. The results had a number of unexpected implications for the Milky Way-LMC-SMC system. The implied three-dimensional velocities were larger than previously believed and close to the escape velocity in a standard 10^12 solar mass Milky Way dark halo, implying that the Clouds may be on their first passage. Also, the relative velocity between the LMC and SMC wa…
The Spitzer-COSMOS survey (S-COSMOS) is a Legacy program (Cycles 2+3) designed to carry out a uniform deep survey of the full 2 sq deg COSMOS field in all seven Spitzer bands (3.6, 4.5, 5.6, 8.0, 24.0, 70.0, 160.0 u). This paper describes the survey parameters, mapping strategy, data reduction procedures, achieved sensitivities to date, and the complete data set for future reference. We show that the observed infrared backgrounds in the S-COSMOS field are within 10% of the predicted background levels. The fluctuations in the background at 24u have been measured and do not show any significant …
We have used the ACS camera on HST to obtain (V,I) photometry for 57,000 red-giant stars in the halo of the Leo elliptical NGC 3377. We use this sample of stars to derive the metallicity distribution function (MDF) for its halo field stars, and comment on its chemical evolution history compared with both larger and smaller E galaxies. Our ACS/WFC field spans a radial range extending from 4 to 18 kpc projected distance from the center of NGC 3377 and thus covers a significant portion of this galaxy's halo. We find that the MDF is broad, reaching a peak at [m/H] ~ -0.6$, but containing virtually…
