In:
Publications of the Astronomical Society of Japan, Oxford University Press (OUP), Vol. 55, No. 3 ( 2003-06-25), p. 573-577
Abstract:
The bright extended X-ray source RX J0419$+$0225, first discovered in the ROSAT All Sky Survey and identified with an S0 galaxy NGC 1550, was observed with ASCA for 48 ks in 1999 August. The detected diffuse X-ray emission is centered at NGC 1550, whose redshift is 0.0123, extending out to at least $15'$, or $210 \,h^{-1}_{75} \,\mathrm{kpc}$, where $h_{75}$ is the Hubble constant in units of $75 \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{Mpc}^{-1}$. The X-ray surface brightness is represented by a $\beta$ model with ${\beta \simeq 0.47}$ and a core radius of $15 \pm 1 \,h^{-1}_{75} \,\mathrm{kpc}$. The temperature and 1–10 keV X-ray luminosity (up to $15'$) of this system were measured as being 1.4 keV and $4.7 \times 10^{42} \,h^{-2}_{75} \,\mathrm{erg} \,\mathrm{s}^{-1}$, respectively. There is no strong evidence of a temperature gradient. Within a radius of $210 \,h^{-1}_{75} \,\mathrm{kpc}$, the estimated total mass of the system becomes $1.5\times 10^{13} \,h^{-1}_{75} \,{{{M}_{\odot}}}$, which is typical of a galaxy group. With the optical information currently available, there are only two other faint galaxies. Including their B-band luminosity, the mass-to-light ratio of the system comes to $\sim 400 \,h_{75} \,{{{M}_{\odot}}}/{{{L}_{\odot}}}$, which is comparable to those of galaxy clusters. Therefore, RX J0419$+$0225 can be regarded as a “dark group candidate” in that it has an unusually high mass-to-light ratio for its optical luminosity. This object is one of the nearest among those ever identified as such candidates.
Type of Medium:
Online Resource
ISSN:
2053-051X
,
0004-6264
DOI:
10.1093/pasj/55.3.573
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2003
detail.hit.zdb_id:
2206640-8
detail.hit.zdb_id:
2083084-1
SSG:
16,12
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