2007/05/31 by L. P. Jenkins, A. E. Hornschemeier, Bahram Mobasher +3 · 30 citations
Medicine · Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Coma (optics) #Coma Cluster #Dwarf galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Luminosity function #Medicine #Physics #Population #Redshift #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/520035
published in The Astrophysical Journal 666(2), 846-862 (IOP Publishing) · 18 pages, 15 figures. Accepted for publication in ApJ. Typos corrected and minor updates to Table 4/Fig.15 to match proofed version
arxiv created 2007/08/03 · openalex publication_date 2007/08/31 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present the first results of a Spitzer IRAC (Infrared Array Camera) wide-field survey of two regions of the Coma Cluster. The observations cover two fields; the first is a 0.733 deg 2 region in the core of the cluster (Coma 1), the second a 0.555 deg 2 off-center region located ~57' (1.7 Mpc) southwest from the core (Coma 3). The IRAC observations, although short 70-90 s exposures, are very sensitive; we detect ~29,200 sources at 3.6 μm over the total ~1.3 deg 2 survey area. We construct 3.6 μm galaxy luminosity functions (LFs) for each field using selection functions based on spectroscopic redshifts. At the bright end, the LFs are well modeled by a traditional Schechter function; ⟨ M ,α 1 ⟩ = ⟨-25.17, - 1.18⟩ and ⟨-24.69, -1.30⟩ for Coma 1 and Coma 3 respectively. However, at the faint end ( M 3.6 μm > -20.5) there is a steep increase in the LF slope in both fields indicative of large numbers of red dwarf galaxies . The reality of this population is examined using SDSS optical counterparts with optical color filtering ( g - r < 1.3). The steep increase can be modeled with a power-law function, with slopes of α 2 = -2.18 (Coma 1) and α 2 = -2.60 (Coma 3), the difference likely indicating a change in environmental effects between the two fields. A qualitative comparison with optical ( B - and R -band) LFs shows that we are likely to be observing a larger population of dwarf galaxies in the near-IR, which may be a low surface brightness (LSB) population that IRAC is particularly sensitive to, or a population too red to be detected in the existing optical surveys down to R ~ 20.