Galaxy Zoo: the dependence of morphology and colour on environment

By Steven Bamford, Robert Nichol, I. Baldry, K. Land, Chris J. Lintott, Kevin Schawinski, A. Slosar, A. Szalay, D. Thomas, Mehri Torki and 14 more. 2008

466 citations recorded by the source corpus.

We analyse the relationships between galaxy morphology, colour, environment and stellar mass using data for over 105 objects from Galaxy Zoo, the largest sample of visually classified morphologies yet compiled. We conclusively show that colour and morphology fractions are very different functions of environment. Both colour and morphology are sensitive to stellar mass. However, at fixed stellar mass, while colour is also highly sensitive to environment, morphology displays much weaker environmental trends. Only a small part of both the morphology–density and colour–density relations can be attributed to the variation in the stellar-mass function with environment. Galaxies with high stellar masses are mostly red in all environments and irrespective of their morphology. Low stellar-mass galaxies are mostly blue in low-density environments, but mostly red in high-density environments, again irrespective of their morphology. While galaxies with early-type morphology do always have higher red fractions, this is subdominant compared to the dependence of red fraction on stellar mass and environment. The colour–density relation is primarily driven by variations in colour fractions at fixed morphology, in particular the fraction of spiral galaxies that have red colours, and especially at low stellar masses. We demonstrate that our red spirals primarily include galaxies with true spiral morphology, and that they constitute an additional population to the S0 galaxies considered by previous studies. We clearly show there is an environmental dependence for colour beyond that for morphology. The environmental transformation of galaxies from blue to red must occur on significantly shorter time-scales than the transformation from spiral to early-type. We also present many of our results as functions of the distance to the nearest galaxy group. This confirms that the environmental trends we present are not specific to the manner in which environment is quantified, but nevertheless provides plain evidence for an environmental process at work in groups. However, the properties of group members show little dependence on the total mass of the group they inhabit, at least for group masses ≳1013M⊙. Before using the Galaxy Zoo morphologies to produce the above results, we first quantify a luminosity-, size- and redshift-dependent classification bias that affects this data set, and probably most other studies of galaxy population morphology. A correction for this bias is derived and applied to produce a sample of galaxies with reliable morphological-type likelihoods, on which we base our analysis.

Subfields: Astronomy and Astrophysics, Computer Vision and Pattern Recognition

View Paper: https://www.semanticscholar.org/paper/c36d3728719a1c51a10aff7a9c7d32ef0b74ede5

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Computer Vision and Pattern Recognition

Citations in the corpus

Physical properties and environments of nearby galaxies (2009, methodology): “Eyeball classifications of tens of thousands of galaxies into general early and late types have been compiled from the general public by the Galaxy Zoo project (Bamford et al. 2009).”
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): “…of several fundamental galaxy properties, most notably for colour - magnitude (or stellar mass), colour - concentration, and colour - morphology (Strateva et al. 2001, Kauffmann et al. 2003, Brinchmann et al. 2004, Baldry et al. 2004, Baldry et al. 2006, Driver et al. 2006, Bamford et al. 2009).”
Galaxy Zoo 2: detailed morphological classifications for 304,122 galaxies from the Sloan Digital Sky Survey (2013, methodology): “The overall effect of this bias is a change in observed morphology fractions as a function of redshift independent of any true evolution in galaxy properties, a trend also seen in the Galaxy Zoo 1 data (Bamford et al. 2009).”
Galaxy pairs in the Sloan Digital Sky Survey – II. The effect of environment on interactions (2010, background): “…Geller 1984), the colours, morphologies and mean star formation rates of galaxies all clearly depend on their local environment (e.g Kauffmann et al. 2004; Balogh et al. 2004; Baldry et al. 2006; Weinmann et al. 2006; Park et al 2007; Skibba et al. 2009; Bamford et al. 2009 and references therein).”
Tracking the impact of environment on the galaxy stellar mass function up to z ~ 1 in the 10 k zCOSMOS sample (2009, background): “It is possible thate transformation of morphology occurs on longer timescales than colour one (Capak et al. 2007a; Smith et al. 2005; Bamford et al. 2009; Wolf et al. 2009), as inferred also from the study of post-starburst galaxies selected in the same zCOSMOS sample (Vergani et al. 2009) or…”
THE GEMINI CLUSTER ASTROPHYSICS SPECTROSCOPIC SURVEY (GCLASS): THE ROLE OF ENVIRONMENT AND SELF-REGULATION IN GALAXY EVOLUTION AT z ∼ 1 (2011, background): “…Linden et al. 2010; Peng et al. 2010; Weinmann et al. 2010), older (e.g., Smith et al. 2006; Cooper et al. 2010b), more metal rich (e.g., Smith et al. 2006; Cooper et al. 2010a), and more frequently have elliptical/S0 morphologies (e.g., Dressler 1980; Postman & Geller 1984; Bamford et al. 2009).”
THE EMISSION BY DUST AND STARS OF NEARBY GALAXIES IN THE HERSCHEL KINGFISH SURVEY (2011, background): “Nonetheless, morphologies and metallicities are notoriously difficult to accurately determine without significant biases, and at fixed stellar mass, galaxies still have a fairly wide distribution of morphologies (e.g., Bamford et al. 2009) and metallicities (e.g., Tremonti et al. 2004).”
Evidence for spin alignment of spiral and elliptical/S0 galaxies in filaments (2012, background): “Key words: methods: statistical – galaxies: evolution – galaxies: general – galaxies: statistics – large-scale structure of Universe.”
The Morphologies of Massive Galaxies at 1<z<3 in the CANDELS-UDS Field: Compact Bulges, and the Rise and Fall of Massive Disks (2012, background): “However, recent studies at both low (Bamford et al. 2009; Masters et al. 2010) and high redshift (McGrath et al. 2008; Stockton et al. 2008; Cameron et al. 2011; van der Wel et al. 2011; McLure et al. 2012) have uncovered a significant population of passive disc-dominated galaxies, providing…”
The zCOSMOS redshift survey: the role of environment and stellar mass in shaping the rise of the morphology-density relation from z ~ 1 (2009, background): “In the Sloan Digital Sky Survey (SDSS) (Blanton et al. 2005; Quintero et al. 2006) and more recently in the GalaxyZoo project (Bamford et al. 2009) it is found that galaxy colour is more strongly correlated with environment than morphology and that colour and morphology bimodalities are largely…”
Star formation and AGN activity in SDSS cluster galaxies (2009, background): “It has been claimed that the dependence of the galaxy population on environment is simply a consequence of a varying galaxy stellar mass function with local density (e.g. Bamford et al. 2009; van den Bosch et al. 2008b).”
Galaxy evolution in groups and clusters: star formation rates, red sequence fractions and the persistent bimodality (2011, background): “…impact on SFR (or colour) is stronger than that on morphology (Kauffmann et al. 2004; Blanton et al. 2005a; Ball, Loveday & Brunner 2008; Bamford et al. 2009): at fixed morphology, SFR still exhibits strong changes with environment, but at fixed SFR, there is almost no dependence of…”
Dependence of galaxy quenching on halo mass and distance from its centre (2012, background): “13 of Bamford et al. (2009) is dominated by satellites.”
The ATLAS3D project - VII. A new look at the morphology of nearby galaxies: the kinematic morphology-density relation (2011, background): “Subsequent obser- ⋆ E-mail: cappellari@astro.ox.ac.uk † Dunlap Fellow vations for local galaxies generally confirmed the originalfinding of a tight and nearly universalT − Σ relation in all environments, extending to the group environment (e.g Postman & Geller 1984; Giovanelli et al. 1986), with sam”
Galaxy Zoo: Passive Red Spirals . (2009, methodology): “We use a cut in the spiral likelihood (corrected for the small bias described in the Appendix of Bamford et al. 2009) of pspiral ≥ 0.8.”
Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, methodology): “This general trend was subsequently confirmed with samples of ever increasing size, reaching a peak with the Galaxy Zoo sample of 105 galaxies (Bamford et al. 2009; Skibba et al. 2009).”
Measures of Galaxy Environment I - What is "Environment"? (2011, result): “Work focused on galaxy clusters have also yielded complementary results (e.g. Poggianti et al. 2008; Bamford et al. 2009; Gallazzi et al. 2009; Rudnick et al. 2009; Wolf et al. 2009).”
Galaxy Zoo 1: data release of morphological classifications for nearly 900 000 galaxies (2010, methodology): “Bamford et al. (2009) used DR6 of the SDSS which only provided spectroscopic coverage for 82 percent of the survey area.”
Environment and self-regulation in galaxy formation (2009, background): “…& Ponman 2003; Kuehn & Ryden 2005; Sorrentino, Antonuccio-Delogu & Rifatto 2006; Holden et al. 2007; Park et al. 2007; van der Wel et al. 2007; Bamford et al. 2009) and intermediate redshift Universe (Dressler et al. 1997; Fasano et al. 2000; Treu et al. 2003; Smith et al. 2005; van der Wel…”