The Recent and Continuing Assembly of Field Elliptical Galaxies by Red Mergers

By P. V. van Dokkum. 2005

345 citations recorded by the source corpus.

We present a study of tidal debris associated with 126 nearby red galaxies, selected from the 1.2 deg2 Multiwavelength Survey by Yale-Chile and the 9.3 deg2 NOAO Deep Wide-Field Survey. In the full sample, 67 galaxies (53%) show morphological signatures of tidal interactions consisting of broad fans of stars, tails, and other asymmetries at very faint surface brightness levels. When restricting the sample to the 86 bulge-dominated early-type galaxies, the fraction of tidally disturbed galaxies rises to 71%, which implies that for every normal undisturbed elliptical there are two that show clear signs of interactions. The tidal features are red and smooth and often extend over >50 kpc. Of the tidally distorted galaxies, about two-thirds are remnants, and one-third are interacting with a companion galaxy. The companions are usually bright red galaxies as well; the median R-band luminosity ratio of the tidal pairs is 0.31, and the median color difference after correcting for the slope of the color-magnitude relation is -0.02 in B - R. If the ongoing mergers are representative for the progenitors of the remnants, ~35% of bulge-dominated galaxies experienced a merger with mass ratio >1 : 4 in the recent past. With further assumptions it is estimated that the present-day mass accretion rate of galaxies on the red sequence ΔM/M = 0.09 ± 0.04 Gyr-1. For a constant or increasing mass accretion rate with redshift, we find that red mergers may lead to an evolution of a factor of 2 in the stellar mass density in luminous red galaxies over the redshift range 0 < z < 1, consistent with recent studies of the evolution of the luminosity density. We conclude that the majority of today's most luminous field elliptical galaxies were assembled at low redshift through mergers of gas-poor, bulge-dominated systems. These dry mergers are consistent with the high central densities of ellipticals, their old stellar populations, and the strong correlations of their properties. It will be interesting to determine whether this mode of merging only plays an important role at low redshift or is relevant for galaxies at any redshift if they exceed a critical mass scale.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/967977213135c33e37f2cc6b4a2cd2055da2020a

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. R. Somerville
4. R. Dav'e
5. Thomas J. Cox
6. C. Conroy
7. A. Dekel
8. P. V. van Dokkum

In Instrumentation

1. P. Hopkins
2. L. Hernquist
3. C. Conroy
4. R. Somerville
5. P. V. van Dokkum
6. Thomas J. Cox
7. R. Dav'e
8. A. Dekel

Citations in the corpus

• The Sloan Lens ACS Survey. II. Stellar Populations and Internal Structure of Early-Type Lens Galaxies (2005, background): “…the assembly of massive early-type galaxies (e.g. Khochfar & Burkert 2003) are the so-called “dry” mergers, i.e. mergers that do not involve a significant amount of cold gas and hence not associated with star formation (see Bell et al. 2006 and van Dokkum 2005 for recent results and discussions).”
• The VIMOS VLT deep survey: the assembly history of the stellar mass in galaxies: from the young to the old universe (2007, neutral): “…a corresponding increase by a factor of 2 of their stellar mass since z ∼ 1, possibly due to so-called “dry mergers” (even if the observational results on major merging and drymerging are still contradictory, see Bell et al. 2005; van Dokkum 2005; Lin et al. 2004, and Renzini 2007, for a summary).”
• The Hierarchical Build-Up of Massive Galaxies and the Intracluster Light since z = 1 (2007, background): “In addition to number counts, estimates of the merger rate of massive galaxies can in principle constrain their assembly history, although current observations fail to present a consistent picture (e.g., van Dokkum 2005; Bell et al. 2006; Masjedi et al. 2006).”
• A Theoretical Interpretation of the Black Hole Fundamental Plane (2007, background): “…(& 3) of successive dry mergers, the observationally estimated rate of∼ 0.5− 1 major dry mergers for a typical massive elliptical (Bell et al. 2006; van Dokkum 2005) implies that the realistic resulting deviations from the BHFP are small (smaller than the internal scatter in the relationi - self).”
• Compact high-redshift galaxies are the cores of the most massive present-day spheroids (2009, background): “1 (see e.g. van Dokkum 2005; Bell et al. 2006; Zheng, Coil & Zehavi 2007; Lin et al. 2008; Conroy & Wechsler 2009).”
• THE GROWTH OF MASSIVE GALAXIES SINCE z = 2 (2009, background): “…that dominates the build-up of the outer regions sincez= 1.5 is likely some form of merging or accretion, consistent with many previous studies (e.g., van Dokkum et al. 1999; van Dokkum 2005; Tran et al. 2005; Bell et al. 2006; White et al. 2007; McIntosh et al. 2008; Naab et al. 2007, 2009).”
• Submillimeter Galaxies at z ~ 2: Evidence for Major Mergers and Constraints on Lifetimes, IMF, and CO-H2 Conversion Factor (2008, background): “Dry major mergers would appear to be a natural choice (van Dokkum 2005; Bell et al. 2006; Naab et al. 2006; Boylan-Kolchin et al. 2006).”
• The formation history of elliptical galaxies (2005, result): “This finding agrees with recent observational results (van Dokkum 2005; Faber et al. 2005; Tran et al. 2005; Bell et al. 2005).”
• THE GREATER IMPACT OF MERGERS ON THE GROWTH OF MASSIVE GALAXIES: IMPLICATIONS FOR MASS ASSEMBLY AND EVOLUTION SINCE z ≃ 1 (2009, background): “(e.g., van Dokkum 2005; Faber et al. 2007; Bell et al. 2007).”
• EVOLUTION OF THE COLOR–MAGNITUDE RELATION IN GALAXY CLUSTERS AT z ∼ 1 FROM THE ACS INTERMEDIATE REDSHIFT CLUSTER SURVEY (2008, background): “Some of them might have gone through merging with fainter red objects (Bell et al. 2004; van Dokkum 2005; Faber et al. 2007).”
• Illuminating Low Surface Brightness Galaxies with the Hyper Suprime-Cam Survey (2017, background): “Such studies have the potential to constrain the mass assembly rate of galaxies (van Dokkum 2005; Tal et al. 2009) and probe the orbital distributions of infalling satellite galaxies (Hendel & Johnston 2015) throughout the universe.”
• The Luminosities, Sizes, and Velocity Dispersions of Brightest Cluster Galaxies: Implications for Formation History (2006, background): “Recent observations suggest that dry mergers are a common formation mechanism for massive early-type galaxies (e.g., van Dokkum 2005).”
• The role of minor mergers in the recent star formation history of early-type galaxies (2007, background): “However, van Dokkum (2005) have recently used very deep optical photometry to show that over 70% of early-types on the optical red sequence show morphological signatures of merging.”
• Determining the Properties and Evolution of Red Galaxies from the Quasar Luminosity Function (2005, background): “Recent observations (Bell et al. 2005; van Dokkum 2005) suggest thatz = 0 spheroids have, on average, undergone∼ 0.5−1 major dry mergers sincez∼ 0.7 (see also Carlberg et al. 1994; Le Fèvre et al. 2000; Patton et al. 2002; Conselice et al. 2003, although de Propris et al. 2005 estimate a…”
• Galaxy growth in the concordance ΛCDM cosmology (2007, background): “…followed Toomre (1976) in arguing that massive elliptical galaxies assembled relatively recently through mergers (e.g. Kauffmann & Charlot 1998; van Dokkum 2005; De Lucia et al. 2006) other authors have used the age and uniformity of their stellar populations and their apparently undiminished…”
• Physical properties and environments of nearby galaxies (2009, background): “While Malin & Carter (1983) found that about 10% of all ellipticals had detectable features, perhaps unsurprisingly it appears that deeper observations reveal structure in a larger fraction. van Dokkum (2005) find that 70% of ellipticals have detectable tidal features down to 27–28 mag arcsec−2.”
• Discriminating Between the Physical Processes that Drive Spheroid Size Evolution (2009, background): “…models (Khochfar & Silk 2006; Hopkins et al. 2009d; Naab et al. 2009) or permitted by observational constraints implying ∼1– 2 major dry mergers (typical mass ratio ∼1:3) per system since z = 2 (van Dokkum 2005; Bell et al. 2006; Lin et al. 2008; Darg et al. 2009a,b; Bridge et al., in preparation).”
• NICMOS Imaging of DRGs in the HDF-S: A Relation between Star Formation and Size at z ~ 2.5 (2006, background): “Mergers that involve substantial gas dissipation may increase the mass density of the remnant (Robertson et al. 2006), while dissipationless, or ‘‘dry,’’ merging increases the size of the galaxies sufficiently to lower their densities (e.g., Nipoti et al. 2003; van Dokkum 2005).”