The ACS Virgo and Fornax Cluster Surveys were unprecedented surveys of early-type galaxies belonging to two benchmark clusters in the local universe, Virgo and Fornax. The surveys were based on ACS imaging from the Hubble Space Telescope (HST), and helped change the way astronomers think about galaxy formation.
Left: An intermediate-luminosity galaxy (VCC1431) in the Virgo Cluster observed with the Advanced Camera for Surveys (ACS) on HST as part of the ACS Virgo Cluster Survey, which targeted 100 early-type galaxies (Cote et al. 2004). Note the central nucleus or “luminosity excess” (see below). A similar survey of the Fornax Cluster, targeting 43 galaxies, is described in Jordan et al. (2007). Top: The ACS/WFC CCDs before the camera was assembled.
The ACS Virgo and Fornax Cluster Surveys were unprecedented surveys of early-type galaxies belonging to two benchmark clusters in the local universe, Virgo and Fornax. The surveys were based on ACS imaging from the Hubble Space Telescope (HST), and helped change the way astronomers think about galaxy formation.
The ACS Virgo and Fornax Cluster Surveys were unprecedented surveys of early-type galaxies belonging to two benchmark clusters in the local universe, Virgo and Fornax. The surveys were based on ACS imaging from the Hubble Space Telescope (HST), and helped change the way astronomers think about galaxy formation.
The ACS Virgo and Fornax cluster surveys produced more than two dozen publications on topics ranging from the core and global structure of early-type galaxies, to globular cluster systems, new families of hot stellar systems (such as “Ultra Compact Dwarf Galaxies” and “Faint Fuzzies”) and the extragalactic distance scale. Some scientific highlights and data products from the surveys include:
-
The first simultaneous characterization of the central and global structure for a large sample of early-type galaxies in the nearby universe (Virgo), made possible by the large field of view of the ACS instrument on HST (Ferrarese et al. 2006a; Cote et al. 2006; Cote et al. 2007).
-
The demonstration that the Sersic family of models provides a remarkably accurate description of the brightness profiles of early-type galaxies spanning nearly three orders of magnitude in luminosity (i.e., from “giant” to “dwarf” galaxies, Ferrarese et al. 2006a). These findings build upon pioneering studies by Caon et al. (1993), Graham et al. (2003), Graham & Guzman (2003) and Jerjen & Binggeli (1997).
-
The finding of a systematic transition from a central luminosity “deficit” to “excess” in the central regions of galaxies, relative to the global Sersic model fit, and a dramatic upward revision of the frequency of distinct nuclear components in the centers of low- and intermediate-luminosity galaxies (Ferrarese et al. 2006a; Cote et al. 2006; Cote et al. 2007). Once again, see the series of earlier papers by Graham and collaborators, including Graham et al. (2003), Graham & Guzman (2003) and Trujillo et al. (2004), as well as Carolla et al. (1998), Boker et al. (2002, 2004), Lotz et al. (2004) and Grant et al. (2005).
-
The realization that these central excesses/nuclei probably arise, for at least some galaxies, through gas inflows and starbursts expected in mergers and accretions, as had been predicted by numerical models (Cote et al. 2006, Cote et al. 2007). See also Mihos & Hernquist (1994), who anticipated these results using pioneering numerical simulations.
-
The discovery that the light “excesses” (i.e., compact stellar nuclei) in the faintest galaxies contain roughly the same percentage of the total galaxy mass as do the Supermassive Black Holes (SBHs) in the brightest galaxies, suggesting a possible link between these two components (Ferrarese et al. 2006b, Cote et al. 2006). See the contemporaneous papers by Rossa et al. (2006) and Wehner and Harris (2006), and the comprehensive subsequent study by Seth et al. (2008).
-
A demonstration that the early-type galaxy populations do not show a dramatic “dichotomy” in terms of their central brightness profile slopes, as was previously believed; the ACS Virgo Cluster Survey was the first study to show that the previously reported class of “power-law galaxies” actually have a two-component structure on small scales (Ferrarese et al. 2006a; Cote et al. 2007). Once again, see also Jerjen & Binggeli (1997), Graham & Guzman (2003), as well as Rest et al. (2001) and Ravindranath et al. (2001).
-
A large and homogeneous catalog of more than ≈ 10,000 globular cluster candidates in early-type galaxies (Jordan et al. 2009).
-
The demonstration that the fundamental properties of globular cluster systems show unexpected continuous trends with host galaxy luminosity. Specific examples include their luminosity functions, size distributions, color/metallicity distributions, and formation efficiencies (Jordan et al.2005, 2006, 2007; Peng et al. 2006a,b, 2008; Mieske et al. 2006, 2010; Sivakoff et al. 2007; Masters et al. 2010; Villegas et al. 2010). These results build upon a number of previous studies by other researchers, including Gebhardt & Kissler-Patig (1998), Larsen et al. (2001) and Kundu et al. (2001).
-
The discovery of Ultra-Compact Dwarf (UCD) galaxies in the Virgo Cluster, the first measurements for the dynamical masses of these systems, and the discovery of an apparently fundamental transition between globular clusters and UCDs at ≈ 2-3 million solar masses (Hasegan et al. 2005).
-
The measurement of accurate SBF distances (i.e., typical errors of ≈ 0.5 Mpc) for a large sample of galaxies in both the Virgo and Fornax Clusters, the direct measurement of the line-of-sight depth of Virgo and a precise measurement of the relative distance of the two clusters (Mei et al. 2005a,b, 2007; Blakeslee et al. 2009).
Please see the science highlights to learn more about these and other topics. To read or download individual papers, see the publications section.
The Survey Teams
The Survey Teams
The ACS Virgo and Fornax Cluster Surveys were unprecedented surveys of early-type galaxies belonging to two benchmark clusters in the local universe, Virgo and Fornax. The surveys were based on ACS imaging from the Hubble Space Telescope (HST), and helped change the way astronomers think about galaxy formation.
Program Galaxies
Left: An intermediate-luminosity galaxy (VCC1431) in the Virgo Cluster observed with the Advanced Camera for Surveys (ACS) on HST as part of the ACS Virgo Cluster Survey, which targeted 100 early-type galaxies (Cote et al. 2004). Note the central nucleus or “luminosity excess” (see below). A similar survey of the Fornax Cluster, targeting 43 galaxies, is described in Jordan et al. (2007). Top: The ACS/WFC CCDs before the camera was assembled.
The Virgo Cluster is the rich cluster nearest to the Milky Way, and the dominant mass concentration in the local universe. It also represents the nearest large collection of early-type (red sequence) galaxies within ~50 Mpc. At a distance of ≈16.5 Mpc, it has historically played a central role in furthering our understanding of galaxy evolution, supermassive black holes, the extragalactic distance scale, the intracluster medium, extragalactic star clusters, and countless other topics in modern astrophysics.
The Virgo Cluster is the rich cluster nearest to the Milky Way, and the dominant mass concentration in the local universe. It also represents the nearest large collection of early-type (red sequence) galaxies within ~50 Mpc. At a distance of ≈16.5 Mpc, it has historically played a central role in furthering our understanding of galaxy evolution, supermassive black holes, the extragalactic distance scale, the intracluster medium, extragalactic star clusters, and countless other topics in modern astrophysics.
The Fornax Cluster is smaller and more compact than Virgo. At a slightly larger distance of ≈20.0 Mpc, it offers an unique opportunity to study the fossil record of galaxy formation in rather different environment than the Virgo Cluster.
The ACS Virgo and Fornax Cluster Surveys
Data Products
This page contains some of the most frequently requested data products from the ACS Virgo and Fornax Surveys, including:
-
Globular cluster catalogs for all ACS Virgo Cluster Survey galaxies (Jordán et al. 2009; ACSVCS Paper XVI)
-
Isophotal parameters and surface brightness profile data for ACS Virgo Cluster Survey galaxies (Ferrarese et al. 2006; ACSVCS Paper VI).
-
Colour distributions and formation efficiency measurements for globular clusters in ACS Virgo Cluster Survey galaxies (Peng et al. 2006, 2008; ACSVCS Papers IX and XV).
-
Fitted and derived parameters for compact stellar nuclei in ACS Virgo Cluster Survey galaxies (Côte et al. 2006; ACSVCS Paper VIII).
-
Surface brightness fluctuation (SBF) measurements and distances for ACS Virgo and Fornax Cluster Survey galaxies (Blakeslee et al. 2009, ACSFCS Paper V; see also Mei et al. 2007, ACSVCS Paper XIII).
Interested researchers, however, are advised to consult the published articles where these data products (and many others) are available in electronic form.
I. Catalogs of Globular Cluster in Early-Type Galaxies
A series of images showing the principle steps involved in the generation of globular cluster catalogs for the ACS Virgo Cluster Survey (see Jordan et al. 2004, 2009, ACSVCS Papers II and XVI).
The properties of globular clusters (and UCDs) belonging to the ACS Virgo Cluster Survey galaxies are discussed primarily in Papers II, III, VII, IX, X, XI, XII, XIV and XV of the Virgo survey series; see the publications section of this website.
A detailed explanation of the methodology used in selecting globular cluster candidates and measuring their photometric and structural properties can be found in ACSVCS Paper XVI. Provided below are formatted ASCII versions of Tables 2, 3, 4 and 5 from that paper.
Table 2: g-band Completeness Curves
Table 3: z-band Completeness Curves
Table 4: Photometric and Structural Catalog of Sources
Table 5: Catalog of Expected Contaminants
II. Isophotal and Structural Analysis of Early-Type Galaxies
The isophotal analysis for the ACS Virgo Cluster Survey galaxies is discussed in Paper VI (Ferrarese et al. 2006a). Provided below are formatted ASCII versions of Tables 1, 3 and 4. These tables conform to the AAS Journal's machine-readable table standards.
Table 1: Global Morphological Properties of Program Galaxies
Table 3: Best Fit parameters to the Luminosity Profile for Program Galaxies
Table 4: Global Structural Parameters for Program Galaxies
In addition, by clicking on the links below, you may download tar files containing figures and data products that may be useful for studies of the ACSVCS galaxies.
1) ACSVCS_images.tar Click to download the ACS view of the galaxy (JPEG format). In each figure, the top panel shows the ACS/WFC/F475W full frame (on the left) and a zoom towards the center (on the right); the grayscale used for the top left panel (full frame) is kept the same for all galaxies; while the grayscale of the top right panel changes from galaxy to galaxy. The bottom left panel shows a contour map of the g-band frame, with levels drawn (for all galaxies) at 0.05,0.1,0.2,0.4,0.8,1.6,3.2,6.4,12.8,25.6 electrons/s/pixel (22.82 mag arcsec-2 to 16.04 mag arcsec-2). Finally, the bottom right panel shows a central section of the g-z color image, with red regions appearing as dark areas and blue regions as light. The linear scale is shown in each panel. All images have been background subtracted.
2) ACSVCS_profiles.tar Click to download a figure showing the isophotal parameters (PDF format). Isophotal parameters are plotted against the `geometric mean' radius rgeo = a(1-e)1/2, with a measured along the semi-major axis of the galaxy, and e equal to the local ellipticity. The panels show surface brightness (in magnitude arcsec-2) in both g (open squares) and z bands (filled squares), g-z color profile (both uncorrected for extinction), ellipticity, position angle (in degrees, measured from North to East) and parameters measuring deviations of the isophotes from pure ellipses. In all panels with the exception of the top right, open and closed symbols refer to g and z-band data respectively. Data are only plotted between 0.049 arcsec (equal to one WFC pixel) and the radius at which the galaxy counts fall below 10% of the sky; sky surface brightnesses are shown by the two short dashed horizontal lines (the fainter sky level is in the g-band). Crosses are used in plotting the color profile when the sum of the (background subtracted) counts in the two filters is lower than the sum of the background levels. Finally, a full horizontal bar in the top-left panel identifies a region where the analysis was performed on images corrected for dust obscuration, while two open horizontal bars identify regions where the fit was performed with fixed values of the ellipticity and major-axis position angle (the topmost bar is for the z-band data, the bottom bar for the g-band data). Higher order coefficients are not shown in these regions.
3) ACSVCS_models.tar to download an ASCII file tabulating the intrinsic (prior to PSF convolution) Sersic or core-Sersic model best fitting the surface brightness profile. The models do not include a nuclear component, when present.
III. Globular Cluster Colour Distributions and Formation Efficiency Measurements
The color distributions of globular clusters in ACS Virgo Cluster Survey galaxies are discussed in Paper IX of that series (Peng et al. 2006a). Provided below are formatted ASCII versions of Tables 1, 3 and 4 from that paper.
Table 2: Color Distributions for ACSVCS Galaxies
The formation efficiencies of globular clusters in ACS Virgo Cluster Survey galaxies are discussed in ACSVCS Paper XV (Peng et al. 2008). Provided below are formatted ASCII versions of Tables 1, 3 and 4 from that paper.
Table 1: Global Properties of ACSVCS Galaxies
IV. Data for Compact Stellar Nuclei in ACSVCS Galaxies
The properties of the nuclear components in ACS Virgo Cluster Survey galaxies (defined as the “excess” central light relative to the inward extrapolation of the global Sersic model) are discussed extensively in Côté et al. (2006; ACSVCS Paper VIII). Interested readers should consult that paper (and also Côté et al. 2007, ACSFCS II and Ferrarese et al. 2006, ACSVCS Paper VI) for more details.
Table 1: Basic Data for Nuclei of Program Galaxies
The analysis of nuclei in ACSFCS program galaxies carried out by Turner et al. (2013) relied on Sersic model fits to the nuclei, rather than King models used in Paper VIII. For consistency with the ACSFCS results, the following table gives Sersic model-based parameters for the ACSVCS nuclei. For more detailes, see Turner et al. (2013).
Table 2: Basic Data for Nuclei of Program Galaxies Using Sersic Models
V. Surface Brightness Fluctuation (SBF) Measurements for ACSVCS and ACSFCS Galaxies
The measurement of surface brightness fluctuation (SBF) distances was a primary goal of the ACS Virgo and Fornax Cluster Surveys. The results for Virgo were presented in three publications (Mei et al. 2005ab, 2007; ACSVCS Papers IV, V and XIII), and final results for the two surveys (including a recalibration of the fluctuation magnitude-color relation) are given in Blakeslee et al. (2009, ACSFCS V). Below are the final SBF distance catalogs for the ACSFCS and ACSVCS samples.
Table 1: SBF Data for ACSFCS Galaxies
Table 2: SBF Data for ACSVCS Galaxies (Blakeslee et al. 2009 recalibration)
(a) Magnified view of the F475W image of VCC 2048 (IC 3773). This is the brightest “dwarf” galaxy in our sample according to the morphological classifications of Binggeli et al. (1985). It is classified as nonnucleated in the Virgo Cluster Catalog, with type d:S0(9). (b–d) Same image, after binning 4 pixels × 4 pixels and convolving with Gaussians of FWHM = 0.5˝, 0.9˝, and 1.4˝, respectively. Figure from Cote et al. (2006, ACSVCS Paper VIII).
A series of images showing the principle steps involved in the generation of globular cluster catalogs for the ACS Virgo Cluster Survey (see Jordan et al. 2004, 2009, ACSVCS Papers II and XVI).
Velocity-distance relation for galaxies from the ACSVCS. The dotted lines shows the undisturbed Hubble Flow in the direction of Virgo for an assumed Hubble Constant of H0 = 73 km s-1 Mpc -1. The predicted distance-velocity relation for a line of sight passing through the cluster, based on the model of Tonry et al. (2000) for large-scale flows in the local universe, is shown by the solid (mean velocity) and dashed curves (±1 limits). Early-type galaxies from the SBF survey of Tonry et al. (2001), which are located with 20° of M87, and which do not appear in the ACSVCS, are plotted as open squares. See Mei et al. (2007, ACSVCS Paper XIII for details).