The Intragroup Medium in Poor Groups of Galaxies

Mulchaey, John S.; Davis, David; Mushotzky, R. F.; Burstein, David

doi:10.1086/176629

Cited by 226 publications

(345 citation statements)

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“…We searched the literature and found three studies that computed stellar, gas, and total masses within the same radius (many more computed a subset of these three quantities, but we only used those that computed all of the quantities in order to ensure self-consistency). Mulchaey et al (1996) used their own ROSAT and optical observations combined with other results from the literature to compile a list of 16 groups with masses computed out to , the maximum radius at which X-R X ray emission could be observed. Hwang et al (1999) Cirimele et al (1997), the squares from Hwang et al (1999), and the diamonds from Mulchaey et al (1996).…”

Section: The Modelmentioning

confidence: 99%

“…Mulchaey et al (1996) used their own ROSAT and optical observations combined with other results from the literature to compile a list of 16 groups with masses computed out to , the maximum radius at which X-R X ray emission could be observed. Hwang et al (1999) Cirimele et al (1997), the squares from Hwang et al (1999), and the diamonds from Mulchaey et al (1996). The solid and dashed lines are median values of the binned distribution for the gas ratio and stellar ratio, respectively.…”

Section: The Modelmentioning

confidence: 99%

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Explaining the Entropy Excess in Clusters and Groups of Galaxies without Additional Heating

Bryan¹

2000

The Astrophysical Journal

139

172

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The X-ray luminosity and temperature of clusters and groups of galaxies do not scale in a self-similar manner. This has often been interpreted as a sign that the intracluster medium has been substantially heated by nongravitational sources. In this Letter, we propose a simple model that instead uses the properties of galaxy formation to explain the available observations. Drawing on available observations, we show that there is evidence that the efficiency of galaxy formation was higher in groups than in clusters. If confirmed, this would deplete the low-entropy gas in groups, increase their central entropy, and decrease their X-ray luminosity. A simple, empirical, hydrostatic model appears to match both the luminosity-temperature relation of clusters and the properties of their internal structure.

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Section: The Modelmentioning

confidence: 99%

Section: The Modelmentioning

confidence: 99%

Explaining the Entropy Excess in Clusters and Groups of Galaxies without Additional Heating

Bryan¹

2000

The Astrophysical Journal

139

172

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“…The general X-ray and optical characteristics of the extended sources in the CDF-N (i.e., their soft X-ray luminosities, apparent X-ray sizes, and weak optical clustering) are most comparable to those of nearby groups of galaxies (e.g., Mulchaey et al 1996;Ponman et al 1996;Helsdon & Ponman 2000). The only exception appears to be source 2, which has a larger angular size and contains an overdensity of unusual objects; it is likely to be a poor-to-moderate Xray cluster at high redshift (i.e., z & 0.7).…”

Section: Basic Nature Of the Extended X-ray Sourcesmentioning

confidence: 99%

The Chandra Deep Field North Survey. IX. Extended X-Ray Sources

Bauer¹,

Alexander²,

Brandt³

et al. 2002

The Astronomical Journal

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The %1 Ms Chandra Deep Field North observation is used to study the extended X-ray sources in the region surrounding the Hubble Deep Field North (HDF-N), yielding the most sensitive probe of extended X-ray emission at cosmological distances to date. A total of six such sources are detected, the majority of which align with small numbers of optically bright galaxies. Their angular sizes, band ratios, and X-ray luminosities-assuming they lie at the same distances as the galaxies coincident with the X-ray emission-are generally consistent with the properties found for nearby groups of galaxies. One source is notably different and is likely to be a poor-to-moderate X-ray cluster at high redshift (i.e., z & 0.7). This source has a large angular extent, a double-peaked X-ray morphology, and an overdensity of unusual objects [very red objects, optically faint (I ! 24) radio and X-ray sources]. Another of the six sources is coincident with several z % 1.01 galaxies located within the HDF-N itself, including the FR I radio galaxy VLA J123644+621133, and is likely to be a group or poor cluster of galaxies at that redshift. We are also able to place strong constraints on the optically detected cluster of galaxies ClG 1236+6215 at z = 0.85 and the wide-angle-tailed radio galaxy VLA J123725+621128 at z $ 1-2; both sources are expected to have considerable associated diffuse X-ray emission, and yet they have rest-frame 0.5-2.0 keV X-ray luminosities of .3 Â 10 42 and .(3-15) Â 10 42 ergs s À1 , respectively. The environments of both sources are either likely to have a significant deficit of hot intracluster gas compared with local clusters of galaxies, or they are X-ray groups. We find the surface density of extended X-ray sources in this observation to be 167 þ97 À67 deg À2 at a limiting soft-band flux of %3 Â 10 À16 ergs cm À2 s À1 . No evolution in the X-ray luminosity function of clusters is needed to explain this value.

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“…The first X-ray detection of the IGrM was made only a decade ago by Mulchaey et al (1993). A more extensive X-ray survey of groups using ROSAT data was carried out by Mulchaey et al (1996a) from which emerged the result that groups with at least one early-type galaxy have higher X-ray luminosities than groups with only late-type galaxies. Mulchaey et al (1996a) gave some possible reasons including that the IGrM of groups with only late-type members had either lower temperatures or lower densities.…”

Section: Introductionmentioning

confidence: 99%

GMRT observations of the group Holmberg 124: Evolution by tidal forces and ram pressure?

Kantharia

Ananthakrishnan

Nityananda

et al. 2005

A&A

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Abstract. We report new radio continuum and 21 cm HI observations using the Giant Metrewave Radio Telescope (GMRT) of the group Holmberg 124 (Ho 124) comprising four late-type galaxies, namely NGC 2820, Mrk 108, NGC 2814 and NGC 2805. The three galaxies, NGC 2820, Mrk 108 and NGC 2814 which are closely located in the sky plane have clearly undergone tidal interactions as seen from the various morphological tidal signatures and debris. Moreover we note various features in the group members which we believe might be due to ram pressure. In this paper, we describe four interesting results emerging from our observations: a) detection of the tidal radio continuum bridge at 330 MHz connecting the galaxies NGC 2820+Mrk 108 with NGC 2814. The radio bridge was discovered at 1465 MHz by van der Hulst & Hummel (1985, A&A, 150, 17). We find that the bridge has a fairly steep spectrum with a spectral index α (S ∝ ν α ) of −1.8 +0.3 −0.2 which is much steeper than the −0.8 quoted by van der Hulst & Hummel (1985); b) detection of other tidal features like the tilted HI and radio continuum disk of NGC 2814, a HI streamer and a radio continuum tail arising from the south of NGC 2814. We also report the detection of a possible tidal dwarf galaxy in HI; c) sharp truncation in the HI distribution in the south of NGC 2820 and in the HI and radio continuum distribution in the north of NGC 2814. The optical disks in both the cases look undisturbed. As pointed out by Davis et al. (1997, AJ, 114, 613), ram pressure affects different components of the interstellar medium to varying degrees. Simple estimates of pressure in different components of the interstellar medium (radio continuum, Hα and HI) in NGC 2820 indicate that ram pressure will significantly influence HI; d) detection of a large one-sided HI loop to the north of NGC 2820. No radio continuum emission or Hα emission is associated with the HI loop. We discuss various scenarios for the origin of this loop including a central starburst, ram pressure stripping and tidal interaction. We do not support the central starburst scenario since the loop is not detected in ionized gas. Using the upper limit on X-ray luminosity of Ho 124 (Mulchaey et al. 2003, ApJS, 145, 39), we estimate an upper limit on the intragroup medium (IGrM) density of 8.8 × 10 −4 cm −3 . For half this electron density, we estimate the ram pressure force of the IGrM to be comparable to the gravitational pull of the disk of NGC 2820. Since tidal interaction has obviously influenced the group, we suggest that the loop could have formed by ram pressure stripping if tidal effects had reduced the surface density of HI in NGC 2820. From the complex observational picture of Ho 124 and the numerical estimates, we suggest that the evolution of the Ho 124 group may be governed by both tidal forces due to the interaction and the ram pressure due to motion of the member galaxies in the IGrM and that the IGrM densities should not be too low (i.e. ≥4 × 10 −4 ). However this needs to be verified by further observations.

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The Intragroup Medium in Poor Groups of Galaxies

Cited by 226 publications

References 0 publications

Explaining the Entropy Excess in Clusters and Groups of Galaxies without Additional Heating

Explaining the Entropy Excess in Clusters and Groups of Galaxies without Additional Heating

The Chandra Deep Field North Survey. IX. Extended X-Ray Sources

GMRT observations of the group Holmberg 124: Evolution by tidal forces and ram pressure?

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