Dissipation and Extra Light in Galactic Nuclei. I. Gas-Rich Merger Remnants

By P. Hopkins, L. Hernquist, Thomas J. Cox, S. Dutta, Barry Rothberg. 2008

140 citations recorded by the source corpus.

We study the origin and properties of “extra” or “excess” central light in the surface brightness profiles of remnants of gas-rich mergers. By combining a large set of hydrodynamical simulations with data on observed mergers that span a broad range of profiles at various masses and degrees of relaxation, we show how to robustly separate the physically meaningful extra light (i.e., the stellar population formed in a compact central starburst during a gas-rich merger) from the outer profile established by violent relaxation acting on stars already present in the progenitor galaxies prior to the final stages of the merger. This separation is sensitive to the treatment of the profile, and we demonstrate that certain fitting procedures can yield physically misleading results. We show that our method reliably recovers the younger starburst population, and examine how the properties and mass of this component scale with the mass, gas content, and other aspects of the progenitors. We consider the time evolution of the profiles in different bands, and estimate the biases introduced by observational studies at different phases and wavelengths. We show that, when appropriately quantified, extra light is ubiquitous in both observed and simulated gas-rich merger remnants, with sufficient mass (~3%-30% of the stellar mass) to explain the apparent discrepancy in the maximum phase-space densities of ellipticals and their progenitor spirals. The nature of this central component provides a powerful new constraint on the formation histories of observed systems and can inform both our studies of their progenitors and our understanding of the global kinematics and structure of spheroids.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/703967c5e78c83b232d01fc7f1cf7dbf22416484

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Citations in the corpus

DETAILED DECOMPOSITION OF GALAXY IMAGES. II. BEYOND AXISYMMETRIC MODELS (2009, background): “…evolution (Rix et al. 2001; Peng et al. 2006a,b), the “extra light” due to gas dissipation in galaxy centers (Kormendy 1999; Kormendy 2 et al. 2009; Hopkins et al. 2008b,a), quasar host galaxies (e.g., Hutchings et al. 1984; McLeod & Rieke 1994; McLure et al. 2000; Jahnke et al. 2004; Sánchez…”
THE METALLICITY EVOLUTION OF INTERACTING GALAXIES (2011, background): “These increases in stellar metallicity are relics from the merger-driven starbursts that leave behind central stellar cusps in merger remnants (Mihos & Hernquist 1994a; Hopkins et al. 2008) and elliptical galaxies (Hopkins et al. 2009a,c).”
WHAT DOES A SUBMILLIMETER GALAXY SELECTION ACTUALLY SELECT? THE DEPENDENCE OF SUBMILLIMETER FLUX DENSITY ON STAR FORMATION RATE AND DUST MASS (2010, methodology): “Thus, at z ∼ 2–3 even a “normal” star-forming galaxy can reach ULIRG luminosities (e.g., Hopkins et al. 2008c, 2010; Daddi et al. 2005, 2007; Dannerbauer et al. 2009).”
The CO-H2 Conversion Factor in Disc Galaxies and Mergers (2011, background): “Similarly, the remnant lies on the fundamental plane (Di Matteo et al. 2005; Robertson et al. 2006; Hopkins et al. 2008a).”
HOW DO DISKS SURVIVE MERGERS? (2008, methodology): “Because gas can dissipate energy, it will then necessarily rapidly fa l into the center of the merging system (essentially free-falling to the center until the collapsing gas becomes self-gravitating; see Hopkins et al. 2008d).”
Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution, and implications for the IMF (2012, methodology): “We use rates from the SEM described in detail in Hopkins et al. (2008c, 2010a,b,c), which we will briefly summarize here.”
THE DEPENDENCE OF QUENCHING UPON THE INNER STRUCTURE OF GALAXIES AT 0.5 ⩽ z < 0.8 IN THE DEEP2/AEGIS SURVEY (2012, background): “The Sérsic indices of the merger products from Hopkins et al. (2008) are high,n ∼> 2.5.”
How Stellar Feedback Simultaneously Regulates Star Formation and Drives Outflows (2015, background): “We not that suppression of starbursts is especially undesirable becaus they are critical for making realistic bulges (Hopkins et al. 2008, 2009a,c).”
How do massive black holes get their gas (2009, background): “In Hopkins et al. (2008a, 2009a), we have demonstrated that this resolution is sufficient to properly resolve not only the mass fractions Table 1.”
Compact high-redshift galaxies are the cores of the most massive present-day spheroids (2009, background): “…the high-redshift systems, or the outcomes of numerical simulations, the expected variation in M∗/L is such that a young, recently formed post-starburst stellar population at the centre of the high-redshift galaxy will have higher L/M∗ than older stars at larger Re (see e.g. Hopkins et al. 2008b).”
The formation of massive, compact galaxies at z = 2 in the Illustris simulation (2014, background): “For example, major, gas-rich mergers where tidal torques drive gas rapidly to the centers of galaxies can provoke intense starbursts there, leaving a compact merger remnant behind (Mihos & Hernquist 1996; Hopkins et al. 2008; Wuyts et al. 2010).”
A general model for the CO–H2 conversion factor in galaxies with applications to the star formation law (2011, background): “…properties of metallicities in mergers (Cox et al. 2006a; Torrey et al. 2011), the broad-band colours of post-starburst galaxies (Snyder et al. 2011), and the structural properties of merging and elliptical galaxies (Hopkins et al. 2008c,d; Hopkins, Cox & Hernquist 2008a; Hopkins et al. 2009).”
CONSTRAINTS ON BLACK HOLE GROWTH, QUASAR LIFETIMES, AND EDDINGTON RATIO DISTRIBUTIONS FROM THE SDSS BROAD-LINE QUASAR BLACK HOLE MASS FUNCTION (2010, background): “This dense stellar remnant is identifiable as a second component in the light profiles of elliptical galaxies (Hopkins et al. 2008a, 2009a, 2009c).”
Moving mesh cosmology: numerical techniques and global statistics (2011, background): “Thus, conclusions drawn from studies of galaxy collisions with SPH, such as the stellar profiles of merger remnants and their evolution (e.g. Hopkins et al. 2008, 2009a,b,c) or the survivability of discs during mergers (Springel & Hernquist 2005), are likely robust to variations in the hydro solver.”
MINOR MERGERS AND THE SIZE EVOLUTION OF ELLIPTICAL GALAXIES (2009, background): “…the required mass and size growth (see also Damjanov et al. 2009) as major dry mergers at most increase the size of a simple one component system by a factor of two and allowing for dark matter halos reduces the size growth further (Nipoti et al. 2003; Naab & Trujillo 2006; Hopkins et al. 2008).”
A model for cosmological simulations of galaxy formation physics: multi-epoch validation (2013, background): “Such an approach for simulations with an unresolved ISM structure is very common (e.g., Ascasibar et al. 2002; Springel & Hernquist 2003a; Springel et al. 2005a; Robertson et al. 2006; Schaye & Dalla Vecchia 2008; Dubois & Teyssier 2008; Hopkins et al. 2008, 2009a,b; Few et al. 2012).”
DISSIPATION AND EXTRA LIGHT IN GALACTIC NUCLEI. II. “CUSP” ELLIPTICALS (2008, methodology): “…figure is available in the online journal.) the early-type or red galaxy mass functions (Bundy et al. 2006; Borch et al. 2006; Fontana et al. 2006; Hopkins et al. 2006c, 2008b), from direct stellar population synthesis studies (Trager et al. 2000; Thomas et al. 2005; Gallazzi et al. 2005), and by…”
MERGERS AND BULGE FORMATION IN ΛCDM: WHICH MERGERS MATTER? (2009, methodology): “…L∗ ellipticals (in terms of their profile shapes, effective radii and fundamental plane correlations, rotation and higher-order kinematics, isophotal shapes, triaxiality, and other prope ties; see e.g. Naab et al. 2006; Cox et al. 2006a; Jesseit et al. 2007, 2009; Hopkins et al. 2008c,a, 2009c)23.”