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J/ApJ/685/235     Host and companion galaxies in the SDSS    (Patton+, 2008)

The luminosity dependence of the galaxy merger rate. Patton D.R., Atfield J.E. <Astrophys. J., 685, 235-246 (2008)> =2008ApJ...685..235P
ADC_Keywords: Galaxies, optical ; Photometry, SDSS ; Redshifts ; Spectroscopy Keywords: galaxies: evolution - galaxies: interactions - galaxies: statistics - surveys Abstract: We measure the number of companions per galaxy (Nc) as a function of r-band absolute magnitude for both the Sloan Digital Sky Survey (DR5) and the Croton and coworkers semianalytic catalog, 2006MNRAS.365...11C, applied to the Millennium Run simulation (Springel et al., 2005Natur.435..629S). For close pairs with projected separations of 5-20kpc/h, velocity differences less than 500km/s, and luminosity ratios between 1:2 and 2:1, we find good agreement between the observations and simulations, with Nc consistently close to 0.02 over the range -22<Mr←18. For larger pair separations, Nc(Mr) instead becomes increasingly steep toward the faint end, implying that luminosity-dependent clustering plays an important role on small scales. Using the simulations to assess and correct for projection effects, we infer that the real-space Nc(Mr) for close pairs peaks at about M* and declines by at least a factor of 2 as Mr becomes fainter. Conversely, by measuring the number density of close companions, we estimate that at least 90% of all major mergers occur between galaxies which are fainter than L*. Finally, measurements of the luminosity density of close companions indicate that L* galaxies likely dominate in terms of the overall importance of major mergers in the evolution of galaxy populations at low redshift. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 73 473 SDSS host galaxies with companions
See also: II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009) J/MNRAS/388/1537 : Galaxy pairs from SDSS-DR2 (McIntosh+, 2008) J/AJ/134/2385 : Occulting galaxy pairs in SDSS (Holwerda+, 2007) J/AJ/127/1883 : Merging galaxies in SDSS EDR (Allam+, 2004) http://www.sdss.org/ : SDSS home page Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 18 A18 --- Host Host object identification (SDSS ObjId) (1) 20- 29 F10.6 deg RAdeg Host right ascension in decimal degrees (J2000) 31- 39 F9.5 deg DEdeg Host declination in decimal degrees (J2000) 41- 47 F7.5 --- z Redshift 49- 54 F6.2 mag rMAG Absolute SDSS r band magnitude (2) 56- 73 A18 --- Comp Companion object identification (SDSS ObjId) (1)
Note (1): The long object identification, which is a bit-encoded integer of run, rerun, camcol, field, object. When the data is reprocessed (rerun), this number will change! Note (2): Throughout this study, we adopt cosmological parameters of Ωm=0.3, ΩΛ=0.7, and H0=100h.km/s/Mpc. For brevity, we express all absolute magnitudes as Mr instead of Mr-5log(h).
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 13-Dec-2010
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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