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X-Ray Thermal Coronae of Galaxies in Hot Clusters: Ubiquity of Embedded Mini-Cooling Cores
We present a systematic investigation of X-ray thermal coronae in 157early-type and 22 late-type galaxies from a survey of 25 hot (kT>3keV), nearby (z<0.05) clusters, based on Chandra archival data. Coolgalactic coronae (kT=0.5-1.1 keV generally) have been found to becommon, >60% in LKs>2L* galaxies.These embedded coronae in hot clusters are generally smaller, lessluminous, and less massive than coronae in poor environments,demonstrating the negative effects of hot cluster environments ongalactic coronae. Nevertheless, these coronae still manage to surviveICM stripping, evaporation, rapid cooling, and powerful AGN outflows,making them a rich source of information about gas stripping,microscopic transport, and feedback processes in the clusterenvironment. Heat conduction across the boundary of the coronae has tobe suppressed by a factor of >~100, which implies that the X-ray gasin early-type galaxies is magnetized and the magnetic field plays animportant role in energy transfer. The luminous, embedded coronae, withhigh central density (0.1-0.4 cm-3), are miniversions ofgroup and cluster cooling cores. As the prevalence of coronae of massivegalaxies implies a long lifetime (>~several Gyr), there must be aheat source inside coronae to offset cooling. While we argue that AGNheating may not generally be the heat source, we conclude that SNheating can be enough as long as the kinetic energy of SNe can beefficiently dissipated. Diffuse thermal coronae have also been detectedin at least 8 of 22 late-type galaxies in our sample. The fraction ofluminous X-ray AGNs (>1041 ergs s-1) is notsmall (~5%) in our sample.
| Evidence of unrelaxed IGM around IC 1262
Aims.A peculiar morphology of the hot gas was discovered at the centerof IC 1262 with the ROSAT HRI. Sensitive Chandra andXMM-Newton data were requested to investigate the characteristics ofthis structure to understand its nature. Methods: .We haveexploited the high resolution and sensitivity of Chandra's ACIS-S toinvestigate the peculiar morphology and spectral characteristics of hotgas in the group around IC 1262. XMM-Newton data areonly partially usable due to very heavy high background contamination,but they are useful to confirm and strengthen the results from Chandra. Results: .The Chandra data show a quite dramatic view of theIC 1262 system: a sharp discontinuity east of thecentral galaxy, with steep drops and a relatively narrow feature over100 kpc long, plus an arc/loop to the N, are all indicative of a turmoilin the high energy component. Their morphologies could suggest them tobe tracers of shocked material caused either by peculiar motions in thesystem or by a recent merger process, but the spectral characteristicsindicate that the structure is cooler than its surroundings. The lack ofevidence of significant structures in the velocity distribution of thegroup members and the estimated scale of the phenomenon make theinterpretation of its physical nature challenging. We review a fewpossible interpretations, in light of similar phenomena observed inclusters and groups. The ram pressure stripping of a bright spiralgalaxy, now near the center of the group, is a promising interpretationfor most of the features observed. The relation with the radio activityrequires a better sampling of the radio parameters that can only beachieved with deeper and higher resolution observations.
| A 70 Kiloparsec X-Ray Tail in the Cluster A3627
We present the discovery of a 70 kpc X-ray tail behind the smalllate-type galaxy ESO 137-001, in the nearby, hot (T=6.5 keV) mergingcluster A3627, from both Chandra and XMM-Newton observations. The tailhas a length-to-width ratio of ~10. It is luminous(L0.5-2keV~1041 ergs s-1), with atemperature of ~0.7 keV and an X-ray Mgas of ~109Msolar (~10% of the galaxy's stellar mass). We interpret thistail as the stripped interstellar medium of ESO 137-001 mixed with thehot cluster medium, with this blue galaxy being converted into agas-poor galaxy. Three X-ray point sources are detected in the axis ofthe tail, which may imply active star formation there. The straightnessand narrowness of the tail also imply that the turbulence in theintracluster medium is not strong on scales of 20-70 kpc.
| Extragalactic large-scale structures behind the southern Milky Way. IV. Redshifts obtained with MEFOS
As part of our efforts to unveil extragalactic large-scale structuresbehind the southern Milky Way, we here present redshifts for 764galaxies in the Hydra/Antlia, Crux and Great Attractor region(266o ≤ℓ ≤338o, | b | 10o), obtained with the Meudon-ESO Fibre Object Spectrograph(MEFOS) at the 3.6-m telescope of ESO. The observations are part of aredshift survey of partially obscured galaxies recorded in the course ofa deep optical galaxy search behind the southern Milky Way(Kraan-Korteweg \cite{Kra00a}; Woudt & Kraan-Korteweg \cite{Wou01}).A total of 947 galaxies have been observed, a small percentage of thespectra (N = 109, 11.5%) were contaminated by foreground stars, and 74galaxies (7.8%) were too faint to allow a reliable redshiftdetermination. With MEFOS we obtained spectra down to the faintestgalaxies of our optical galaxy survey, and hence probe large-scalestructures out to larger distances (v 30 000 km s-1)than our other redshift follow-ups using the 1.9-m telescope at theSouth African Astronomical Observatory (Kraan-Korteweg et al.\cite{Kra95}; Fairall et al. \cite{Fai98}; Woudt et al. \cite{Wou99})and the 64-m Parkes radio telescope (Kraan-Korteweg et al.\cite{Kra02}). The most distinct large-scale structures revealed in thesouthern Zone of Avoidance are discussed in context to known structuresadjacent to the Milky Way.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/415/9 Based onobservations taken at the European Southern Observatory, La Silla,Chile.
| Serendipitous detection of galaxies behind the Milky Way from the DENIS survey
A search has been undertaken at Lyon Observatory to identify, by eye,galaxy candidates at galactic latitudes lower than +/-15 degrees on theDENIS J and K-band images. This paper presents a list of 2028 objectsthat were serendipitously detected throughout the DENIS survey.Cross-identification with galaxy entries in the LEDA Database has beenperformed. Comparison with the second release of the 2MASS survey led toa satisfactory agreement of J band magnitudes (std. dev. = 0.3 mag). Thedistribution of galaxy candidates along the Galactic Plane shows aconcentration near the galactic longitude l=305 deg . As a by product ofthis inspection of J and K images some interesting galactic objects werefound (star clusters and nebulae). Based on observations collected atthe European Southern Observatory, La Silla, Chile. The catalog (Table1) is only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.188.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/387/1
| A catalogue of galaxies behind the southern Milky Way. II. The Crux and Great Attractor regions (l~ 289o to 338o)
In this second paper of the catalogue series of galaxies behind thesouthern Milky Way, we report on the deep optical galaxy search in theCrux region (289o <= l <= 318o and-10o <= b <= 10o) and the Great Attractorregion (316o <= l <= 338o and-10o <= b <= 10o}). The galaxy cataloguesare presented, a brief description of the galaxy search given, as wellas a discussion on the distribution and characteristics of the uncoveredgalaxies. A total of 8182 galaxies with major diameters D >~ 0.2arcmin were identified in this ~ 850 square degree area: 3759 galaxiesin the Crux region and 4423 galaxies in the Great Attractor region. Ofthe 8182 galaxies, 229 (2.8%) were catalogued before in the optical (3in radio) and 251 galaxies have a reliable (159), or likely (92)cross-identification in the IRAS Point Source Catalogue (3.1%). A numberof prominent overdensities and filaments of galaxies are identified.They are not correlated with the Galactic foreground extinction andhence indicative of extragalactic large-scale structures. Redshiftsobtained at the South African Astronomical Observatory (SAAO) for 518 ofthe newly catalogued galaxies in the Crux and Great Attractor regions(Fairall et al. \cite{Fairall98}; Woudt et al. \cite{Woudt99}) confirmdistinct voids and clusters in the area here surveyed. With this opticalgalaxy search, we have reduced the width of the optical ``Zone ofAvoidance'' for galaxies with extinction-corrected diameters larger than1.3 arcmin from extinction levels AB >= 1.0m toAB >= 3.0m: the remaining optical Zone of Avoidance is nowlimited by | b | <~ 3o (see Fig. \ref{cruxf1new}). The twooptical catalogues and their respective listings of IRAScross-identifications are available in electronic format at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/380/441
| Extragalactic large-scale structures behind the southern Milky Way. III. Redshifts obtained at the SAAO in the Great Attractor region
In the third of a series of papers on large-scale structures behind thesouthern Milky Way, we report here on redshifts obtained at the SouthAfrican Astronomical Observatory (SAAO) in the Great Attractor region(318deg <~ l <~ 340deg , |b| <= 10deg , Woudt 1998). Thisregion encompasses the peak in the reconstructed mass density field,associated with the Great Attractor (Kolatt et al. 1995, Dekel et al.1998) and covers the crossing of the Supergalactic Plane with theGalactic Plane. Our deep optical galaxy search in the Zone of Avoidance(ZOA) in this region (Woudt 1998) has resulted in the detection of 4423galaxies with observed diameters larger than 0.2 arcmin. We haveobtained reliable redshifts for 309 galaxies of the 4423 galaxies withthe ``Unit'' spectrograph (first with a Reticon, then with a CCDdetector) at the 1.9-m telescope of the SAAO. An additional 13 tentativeredshifts are presented. Before our survey, 127 galaxies had apreviously recorded redshift (NED and SRC96). Given a small overlap withthe literature (44 galaxies), we present here redshifts for 265 galaxiesthat had no previous recorded velocity. In addition, we present centralvelocity dispersion (sigma_o ) measurements for 34 galaxies in ACO 3627.It is known that the Great Attractor (GA) region is overdense ingalaxies at a redshift-distance of v ~ 5000 {km s-1 }(Fairall 1988, Dressler 1991, Visvanathan & Yamada 1996, di Nella etal. 1997). We realise here, however, that the Great Attractor region isdominated by ACO 3627 (hereafter referred to as the Norma cluster), ahighly obscured, nearby and massive cluster of galaxies close to theplane of the Milky Way (l, b, v) = (325.3deg , -7.2deg , 4844 {kms-1 }) (Kraan-Korteweg et al. 1996, Woudt 1998). Previousredshift surveys in the GA region have failed to gauge the significanceof the Norma cluster, primarily due to the diminishing effects of theGalactic foreground extinction on the partially obscured galaxies. Inthe absence of the obscuring effects of the Milky Way, the Norma clusterwould have appeared as prominent as the well-known Coma cluster, butnearer in redshift-space. This cluster most likely marks the bottom ofthe potential well of the Great Attractor (Woudt 1998). All the tablesare only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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