📝 Original Info
- Title: A Large X-ray Sample of Fossil Groups
- ArXiv ID: 0910.4171
- Date: 2009-10-23
- Authors: - Eric D. Miller¹ - Eli Rykoff² - Renato de Alencar Dupke³⁴ - Claudia Mendes de Oliveira⁵ - Timothy McKay⁴ - Benjamin Koester⁶ Affiliations: ¹ MIT Kavli Institute, ² UCSB, ³ ON/MCT, ⁴ University of Michigan, ⁵ Universidade de São Paulo, ⁶ University of Chicago
📝 Abstract
We present Chandra snapshot observations of the first large X-ray sample of optically identified fossil groups. For 9 of 14 candidate groups, we are able to determine the X-ray luminosity and temperature, which span a range typical of large ellipticals to rich groups of galaxies. We discuss these initial results in the context of group IGM and central galaxy ISM evolution, and we also describe plans for a deep X-ray follow-up program.
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📄 Full Content
arXiv:0910.4171v1 [astro-ph.CO] 21 Oct 2009
Highlights of Astronomy, Volume 15
XXVIIth IAU General Assembly, August 2009
Ian F Corbett, ed.
c⃝2009 International Astronomical Union
DOI: 00.0000/X000000000000000X
A Large X-ray Sample of Fossil Groups
Eric D. Miller1, Eli Rykoff2, Renato de Alencar Dupke3,4, Claudia
Mendes de Oliveira5, Timothy McKay4, Benjamin Koester6
1MIT Kavli Institute, 2UCSB, 3ON/MCT, 4U. Michigan, 5USP, 6U. Chicago
Abstract. We present Chandra snapshot observations of the first large X-ray sample of opti-
cally identified fossil groups. For 9 of 14 candidate groups, we are able to determine the X-ray
luminosity and temperature, which span a range typical of large ellipticals to rich groups of
galaxies. We discuss these initial results in the context of group IGM and central galaxy ISM
evolution, and we also describe plans for a deep X-ray follow-up program.
Keywords. galaxies: clusters: general, X-rays: galaxies: clusters, surveys
Fossil groups (FGs) are systems dominated by a single, giant elliptical galaxy, yet their
X-ray emission indicates a deeper cluster-scale gravitational potential. They are thought
to be old, undisturbed galaxy groups, however these systems may be younger or more
active than previously thought (see Dupke et al. in these proceedings). These results are
complicated by the small number of FGs with deep X-ray data.
To address this, we have constructed a sample of 15 FG candidates from the maxBCG
cluster catalog (Koester et al. 2007), using the criteria 0.09 < z < 0.15, LBCG > 9 ×
1011L⊙, and ∆i > 2.0 between the BCG and second ranked galaxy within R200/2 (see
Figure 1). We have obtained 5–10 ksec Chandra snapshot observations of 14 targets, and
we detect diffuse X-ray emission from 11 of them at > 90% confidence, measuring TX
for 9 of these. One detection is shown in Figure 2. The measured LX and TX are similar
to what is expected for groups of galaxies. Deep follow-up with XMM is necessary to
measure TX profiles, surface brightness profiles, concentration, and abundances, thereby
constraining the formation mechanism of these peculiar but numerous systems.
References
Koester, B.P. 2007, ApJ, 660, 239
1
10
LBCG (1010 Lsun)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
∆i (mag)
Figure 1. Magnitude differential vs. BCG
luminosity for all maxBCG clusters with
9 < N200 < 25; open squares identify the 15
FG candidates. Diamonds show known FGs.
Figure 2. SDSS J0856+0553, a z = 0.09 FG
candidate. The X-ray image is plotted over the
SDSS g, r, i composite image.
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Reference
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