Galaxy Zoo: the properties of merging galaxies in the nearby Universe – local environments, colours, masses, star formation rates and AGN activity

By D. Darg, S. Kaviraj, Chris J. Lintott, Kevin Schawinski, M. Sarzi, Steven Bamford, J. Silk, Dan Andreescu, P. Murray, Robert Nichol and 5 more. 2009

152 citations recorded by the source corpus.

Following the study of Darg et al., we explore the environments, optical colours, stellar masses, star formation and active galactic nucleus activity in a sample of 3003 pairs of merging galaxies drawn from the Sloan Digital Sky Survey using visual classifications from the Galaxy Zoo project. While Darg et al. found that the spiral-to-elliptical ratio in (major) mergers appeared higher than that of the global galaxy population, no significant differences are found between the environmental distributions of mergers and a randomly selected control sample. This makes the high occurrence of spirals in mergers unlikely to be an environmental effect and must therefore arise from differing time-scales of detectability for spirals and ellipticals. We find that merging galaxies have a wider spread in colour than the global galaxy population, with a significant blue tail resulting from intense star formation in spiral mergers. Galaxies classed as star-forming using their emission-line properties have average star formation rates approximately doubled by the merger process though star formation is negligibly enhanced in merging elliptical galaxies. We conclude that the internal properties of galaxies significantly affect the time-scales over which merging systems can be detected (as suggested by recent theoretical studies) which leads to spirals being ‘over-observed’ in mergers. We also suggest that the transition mass 3 × 1010 M⊙, noted by Kauffmann et al., below which ellipticals are rare could be linked to disc survival/destruction in mergers.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/bf2d1d22c94eb7817e4088d66eaa95a1c1893127

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Citations in the corpus

Galaxy pairs in the Sloan Digital Sky Survey – V. Tracing changes in star formation rate and metallicity out to separations of 80 kpc (2012, background): “With large data sets, such as those obtained from large surveys, the imaging is often not very deep, and the samples are large enough that vi- sual classifications quickly become impractical (although see Darg et al. 2010).”
The green valley is a red herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early-and late-type galaxies (2014, background): “…2009a; Masters et al. 2010b) and about the link between galaxy evolution and environment (e.g. Bamford et al. 2009; Skibba et al. 2009), mergers (Darg et al. 2010a, b; Kaviraj et al. 2012; Teng et al. 2012), unusual galaxy types (Cardamone et al. 2009; Lintott et al. 2009; Keel et al. 2012) and…”
Galaxy Zoo 1: data release of morphological classifications for nearly 900 000 galaxies (2010, methodology): “Darg et al. (2010a), in their study of merging galaxies, found that all galaxies with a fraction of 40 per cent or more of their vote in the ‘merger’ category were, in fact, true mergers.”
Galaxy pairs in the Sloan Digital Sky Survey – VIII. The observational properties of post-merger galaxies (2013, methodology): “…Reichard et al. 2009; Peeples et al. 2009; Alonso, Michel-Dansac & Lambas 2010; Scudder et al. 2012b; Chung et al. 2013), morphology (Ellison et al. 2010; Darg et al. 2010; Casteels et al. 2013), gas consumption (Fertig et al. in preparation; Scudder et al. in prepa- c© 0000 RAS ar X iv :1 30 8.”
Bulge mass is king: the dominant role of the bulge in determining the fraction of passive galaxies in the Sloan Digital Sky Survey (2014, background): “…minor galaxy mergers and interactions can give rise to enhanced star formation rates, and hence elevated gas depletion (e.g. Ellison et al. 2008, Darg et al. 2010, Patton et al. 2013, Hung et al. 2013), as well as increased supernova and stellar feedback which may also accelerate the transition…”
Galaxy pairs in the Sloan Digital Sky Survey – II. The effect of environment on interactions (2010, background): “Nonetheless, a significant fraction of galaxies even at high densities have low∆v andrp, and yet galaxies in high density environments do not seem to exhibit much triggered star formation (Darg et al. 2010; Perez et al. 2009b).”
MAJOR GALAXY MERGERS ONLY TRIGGER THE MOST LUMINOUS ACTIVE GALACTIC NUCLEI (2012, background): “Hence, visual classification is still the most reliable option to determine if a galaxy is experiencing a major merger (Darg et al. 2010).”
What drives the growth of black holes (2011, methodology): “Using morphological classifications of SDSS galaxies from the Galaxy Zoo project (Lintott et al., 2011), Darg et al. (2010) estimated that only ≈ 1% of AGNs reside in systems clearly undergoing a major merger.”
The DEEP3 Galaxy Redshift Survey: the impact of environment on the size evolution of massive early-type galaxies at intermediate redshift (2011, background): “…are not preferentially found in overdense regions at z ∼ 1 (Coil et al. 2007), mergers are more common in higher density environments such as galaxy groups (Cavaliere, Colafrancesco & Menci 1992; McIntosh et al. 2008; Wetzel et al. 2008; Fakhouri & Ma 2009; Darg et al. 2010; Lin et al. 2010).”
A CATALOG OF BULGE+DISK DECOMPOSITIONS AND UPDATED PHOTOMETRY FOR 1.12 MILLION GALAXIES IN THE SLOAN DIGITAL SKY SURVEY (2011, background): “As explained in Patton et al. (2011), the presence of these outliers in the official SDSS photometry was ascribed in the literature to a new population of extremely-red pair galaxies (e.g., Alonso et al. 2006; Perez et al. 2009; Darg et al. 2010).”