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Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS

Balogh, Michael and Eke, Vince and Miller, Chris and Lewis, Ian and Bower, Richard and Couch, Warrick and Nichol, Robert and Bland-Hawthorn, Joss and Baldry, Ivan K. and Baugh, Carlton and Bridges, Terry and Cannon, Russell and Cole, Shaun and Colless, Matthew and Collins, Chris and Cross, Nicholas and Dalton, Gavin and De Propris, Roberto and Driver, Simon P. and Efstathiou, George and Ellis, Richard S. and Frenk, Carlos S. and Glazebrook, Karl and Gomez, Percy and Gray, Alex and Hawkins, Edward and Jackson, Carole and Lahav, Ofer and Lumsden, Stuart and Maddox, Steve and Madgwick, Darren and Norberg, Peder and Peacock, John A. and Percival, Will and Peterson, Bruce A. and Sutherland, Will and Taylor, Keith (2004) Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS. Monthly Notices of the Royal Astronomical Society, 348 (4). pp. 1355-1372. ISSN 0035-8711. doi:10.1111/j.1365-2966.2004.07453.x.

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We analyse the observed correlation between galaxy environment and Hα emission-line strength, using volume-limited samples and group catalogues of 24 968 galaxies at 0.05 < z < 0.095, drawn from the 2dF Galaxy Redshift Survey (M_(bJ) < −19.5) and the Sloan Digital Sky Survey (Mᵣ < −20.6). We characterize the environment by: (1) Σ₅, the surface number density of galaxies determined by the projected distance to the fifth nearest neighbour; and (2) ρ1.1 and ρ5.5, three-dimensional density estimates obtained by convolving the galaxy distribution with Gaussian kernels of dispersion 1.1 and 5.5 Mpc, respectively. We find that star-forming and quiescent galaxies form two distinct populations, as characterized by their Hα equivalent width, W₀(Hα). The relative numbers of star-forming and quiescent galaxies vary strongly and continuously with local density. However, the distribution of W₀(Hα) amongst the star-forming population is independent of environment. The fraction of star-forming galaxies shows strong sensitivity to the density on large scales, ρ5.5, which is likely independent of the trend with local density, ρ1.1.We use two differently selected group catalogues to demonstrate that the correlation with galaxy density is approximately independent of group velocity dispersion, for σ = 200–1000 km s⁻¹. Even in the lowest-density environments, no more than ∼70 per cent of galaxies show significant Hα emission. Based on these results, we conclude that the present-day correlation between star formation rate and environment is a result of short-time-scale mechanisms that take place preferentially at high redshift, such as starbursts induced by galaxy–galaxy interactions.

Item Type:Article
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URLURL TypeDescription Paper
Bland-Hawthorn, Joss0000-0001-7516-4016
Baugh, Carlton0000-0002-9935-9755
Colless, Matthew0000-0001-9552-8075
Ellis, Richard S.0000-0001-7782-7071
Norberg, Peder0000-0002-5875-0440
Additional Information:© 2004 RAS. Accepted 2003 November 20. Received 2003 November 20; in original form 2003 September 25. We gratefully acknowledge the efforts of all persons whose contributions led to the success of the 2dFGRS and SDSS, which in turn have made this work possible. In addition, MLB acknowledges helpful discussions with Ann Zabludoff, Tadayuki Kodama, Masayuki Tanaka and Diego Lambas; also, he thanks Carolyn McCoey for a careful reading of the manuscript, which substantially improved its clarity. MLB and RGB acknowledge financial support from PPARC fellowships, numbered PPA/P/S/2001/00298 and PPA/Y/S/2001/00407, respectively. WJC acknowledges the financial support of the Australian Research Council throughout the course of this work.
Funding AgencyGrant Number
Particle Physics and Research Council (PPARC)PPA/P/S/2001/00298
Particle Physics and Research Council (PPARC)PPA/Y/S/2001/00407
Australian Research CouncilUNSPECIFIED
Subject Keywords:galaxies: clusters: general – galaxies: evolution – galaxies: interactions.
Issue or Number:4
Record Number:CaltechAUTHORS:20200708-151733389
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Official Citation:Michael Balogh, Vince Eke, Chris Miller, Ian Lewis, Richard Bower, Warrick Couch, Robert Nichol, Joss Bland-Hawthorn, Ivan K. Baldry, Carlton Baugh, Terry Bridges, Russell Cannon, Shaun Cole, Matthew Colless, Chris Collins, Nicholas Cross, Gavin Dalton, Roberto De Propris, Simon P. Driver, George Efstathiou, Richard S. Ellis, Carlos S. Frenk, Karl Glazebrook, Percy Gomez, Alex Gray, Edward Hawkins, Carole Jackson, Ofer Lahav, Stuart Lumsden, Steve Maddox, Darren Madgwick, Peder Norberg, John A. Peacock, Will Percival, Bruce A. Peterson, Will Sutherland, Keith Taylor, Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS, Monthly Notices of the Royal Astronomical Society, Volume 348, Issue 4, March 2004, Pages 1355–1372,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104289
Deposited By: Rebecca Minjarez
Deposited On:10 Jul 2020 15:34
Last Modified:16 Nov 2021 18:30

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