The ACS Virgo Cluster Survey. VI. Isophotal Analysis and the Structure of Early‐Type Galaxies

Abstract

We present a detailed analysis of the morphology, isophotal parameters and surface brightness profiles for 100 early-type members of the Virgo Cluster, from dwarfs (M B = −15.1 mag) to giants (M B = −21.8 mag). Each galaxy has been imaged in two filters, closely resembling the Sloan g and z passbands, using the Advanced Camera for Surveys on board the Hubble Space Telescope. Dust and complex morphological structures are common. Dust is detected in as many as 18, preferentially bright, galaxies. The incidence rate in the 26 galaxies brighter than B T = 12.15 mag, which form a magnitude limited sample, is 42%. The amount and distribution of dust show no obvious correlations with galaxy morphology; dust features range from faint wisps and patches on tens of parsec scales, to regular, highly organized kpc-scale dust disks. Blue star clusters are interspersed within the larger, clumpier dust disks, while thin, dynamically cold stellar disks are seen in association with the smaller, uniform nuclear dust disks. Kiloparsec-scale stellar disks, bars, and nuclear stellar disks are seen in 60% of galaxies with intermediate luminosity (−20 M B −17). In at least one case (VCC 1938 = NGC 4638), the large-scale stellar disk has a sharp inner edge, possibly produced when disk instabilities led to the formation of a (now dissolved) bar. This process might indeed be seen unfolding in one galaxy, VCC 1537 (=NGC 4528). A spiral structure might be present in VCC 1199, an elliptical companion of M49. In dwarf galaxies, spiral structures are confirmed in VCC 856 and detected for the first time in VCC 1695. Surface brightness profiles, ellipticities, major axis position angles, and isophotal shapes are derived typically within 8 kpc from the center for the brightest galaxies, and 1.5 kpc for the faintest systems, with a resolution (FWHM) of 7 pc. For all but 10 of the galaxies, the surface brightness profiles are well described by a Sérsic model with index n which increases steadily from the fainter to the brightest galaxies. In agreement with previous claims, the inner profiles (typically within 100 pc of the center) of eight of the 10 brightest galaxies, to which we will refer as "core" galaxies, are lower than expected based on an extrapolation of the outer Sérsic model, and are better described by a single power-law function. Core galaxies are clearly distinct in having fainter central surface brightness, µ 0 , and shallower logarithmic slope of the inner surface brightness profile, γ, than expected based on the extrapolation of the trend followed by the rest of the sample, for which both µ 0 and γ increase steadily with galaxy magnitude. Large-scale, global properties also set core galaxies apart: the effective radius in particular is found to be almost one order of magnitude larger than for only slightly less luminous non-core galaxies. Contrary to previous claims, we find no evidence in support of a strong bimodal behavior of the inner profile slope, γ; in particular the γ distribution for galaxies which do not show evidence of m...

Dissipation and the Fundamental Plane: Observational Tests

“…However, there is hope: Mihos & Hernquist (1994c) predicted that these dissipational starbursts should leave an observable signature in the surface brightness profiles of remnants, in the form of a steep departure from the outer de Vaucouleurs (1948) r 1 = 4 -law distribution in the inner regions: i.e., a central ''extra light'' component above the inward extrapolation of the outer profile. Observations have now uncovered distinctive evidence for this two-component structure in local ellipticals (Kormendy 1999;Kormendy et al 2008;Ferrarese et al 2006), classical bulges (Balcells et al 2007), and recent merger remnants (Hibbard & Yun 1999;Rothberg & Joseph 2004). With the combination of Hubble Space Telescope (HST ) and ground-based photometry, it now appears that such components are ubiquitous (Kormendy et al 2008), with mass ranges and spatial extents comparable to those expected from observations of ongoing merger-induced starbursts and numerical simulations.…”

“…Specifically, we consider three samples of ellipticals and a compilation of remnants of recent gas-rich mergers. The first is the V-band Virgo elliptical survey of Kormendy et al (2008) based on the complete sample of Virgo galaxies down to extremely faint systems in Binggeli et al (1985) (the same sample studied in Côté et al 2006;Ferrarese et al 2006). Kormendy et al (2008) combine observations from a large number of sources (including Bender et al 1988;R.…”

An extensive catalogue of early-type galaxies in the nearby Universe

“…Note that the Re listed in Bender et al (1992) are considerably larger than the ones listed here, since the distance estimates that they adopt for the galaxies are larger than the ones listed in Tab (2). A '3' indicates that Re is based on the angular Re in the gband in Ferrarese et al (2006) galaxy is part of the Coma cluster and its Re is based on the physical Re published by . A '7' indicates galaxies in the cluster Abell 496 whose Re are based on their angular Re in Chilingarian et al (2008).…”

Eötvös experiments with supermassive black holes

“…and ∆θ = 0.014 ∆ 1 − ∆ cos 3 i arcseconds (18) where we have extrapolated the theoretical stellar mass profile of Walsh et al (2013) out to 10 arcseconds, slightly beyond the break radius of 7.15 arcseconds determined by Ferrarese et al (2006) where the surface brightness profile steepens. The position of the black hole can in principle be determined to microarcsecond precision with microwave interferometry (Broderick et al 2011).…”