SPITZER/IRAC LOW SURFACE BRIGHTNESS OBSERVATIONS OF THE VIRGO CLUSTER

Journal Article · Sun Jul 10 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/735/2/76· OSTI ID:21578413

Krick, J E; Desai, V; Murphy, E; Surace, J ^[1]; Bridge, C; Neill, J ^[2]; Mihos, J C ^[3]; Rudick, C ^[4]

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1. Spitzer Science Center, MS 220-6, California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA 91125 (United States)
2. Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
3. Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States)
4. ETH Zurich, Institute of Astronomy, CH8093 Zurich (Switzerland)

We present 3.6 and 4.5 {mu}m Spitzer Infrared Array Camera (IRAC) imaging over 0.77 deg{sup 2} at the Virgo cluster core for the purpose of understanding the formation mechanisms of the low surface brightness intracluster light (ICL) features. Instrumental and astrophysical backgrounds that are hundreds of times higher than the signal were carefully characterized and removed. We examine ICL plumes as well as the outer halo of the giant elliptical M87. For two ICL plumes, we use optical colors to constrain their ages to be greater than 3 and 5 Gyr, respectively. Upper limits on the IRAC fluxes constrain the upper limits to the masses, and optical detections constrain the lower limits to the masses. In this first measurement of mass of ICL plumes we find masses in the range of 5.5 x 10{sup 8} - 4.5 x 10{sup 9} and 2.1 x 10{sup 8}-1.5 x 10{sup 9} M{sub sun} for the two plumes for which we have coverage. Given their expected short lifetimes, and a constant production rate for these types of streams, integrated over Virgo's lifetime, they can account for the total ICL content of the cluster, implying that we do not need to invoke ICL formation mechanisms other than gravitational mechanisms leading to bright plumes. We also examined the outer halo of the giant elliptical M87. The color profile from the inner to outer halo of M87 (160 kpc) is consistent with either a flat or optically blue gradient, where a blue gradient could be due to younger or lower metallicity stars at larger radii. The similarity of the age predicted by both the infrared and optical colors (> a few gigayears) indicates that the optical measurements are not strongly affected by dust extinction.

• OSTI ID: 21578413
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 735; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BRIGHTNESS
EVOLUTION
GALACTIC EVOLUTION
GALAXY CLUSTERS
OPTICAL PROPERTIES
PHOTOMETRY
PHYSICAL PROPERTIES