共查询到20条相似文献，搜索用时 62 毫秒
1.
2.
Jesper Rasmussen † Trevor J. Ponman Lourdes Verdes-Montenegro Min S. Yun Sanchayeeta Borthakur 《Monthly notices of the Royal Astronomical Society》2008,388(3):1245-1264
Galaxies in compact groups tend to be deficient in neutral hydrogen compared to isolated galaxies of similar optical properties. In order to investigate the role played by a hot intragroup medium (IGM) for the removal and destruction of H i in these systems, we have performed a Chandra and XMM–Newton study of eight of the most H i deficient Hickson compact groups. Diffuse X-ray emission associated with an IGM is detected in four of the groups, suggesting that galaxy–IGM interactions are not the dominant mechanism driving cold gas out of the group members. No clear evidence is seen for any of the members being currently stripped of any hot gas, nor for galaxies to show enhanced nuclear X-ray activity in the X-ray bright or most H i deficient groups. Combining the inferred IGM distributions with analytical models of representative disc galaxies orbiting within each group, we estimate the H i mass-loss due to ram-pressure and viscous stripping. While these processes are generally insufficient to explain observed H i deficiencies, they could still be important for H i removal in the X-ray bright groups, potentially removing more than half of the interstellar medium in the X-ray bright HCG 97. Ram pressure may also have facilitated strangulation through the removal of galactic coronal gas. In X-ray undetected groups, tidal interactions could be playing a prominent role, but it remains an open question whether they can fully account for the observed H i deficiencies. 相似文献
3.
4.
5.
I. Sakelliou D. M. Acreman M. J. Hardcastle M. R. Merrifield T. J. Ponman I. R. Stevens 《Monthly notices of the Royal Astronomical Society》2005,360(3):1069-1076
We present XMM–Newton observations of the wake–radio galaxy system 4C 34.16, which shows a cool and dense wake trailing behind the host galaxy of 4C 34.16. A comparison with numerical simulations is enlightening, as they demonstrate that the wake is produced mainly by ram pressure stripping during the galactic motion through the surrounding cluster. The mass of the wake is a substantial fraction of the mass of the X-ray halo of an elliptical galaxy. This observational fact supports a wake formation scenario similar to that recently demonstrated numerically by Acreman et al.: the host galaxy of 4C 34.16 has fallen into its cluster, and is currently crossing its central regions. A substantial fraction of its X-ray halo has been stripped by ram pressure, and remains behind to form the galaxy wake. 相似文献
6.
7.
Henrique A. Fraquelli T. Storchi-Bergmann N. A. Levenson 《Monthly notices of the Royal Astronomical Society》2003,341(2):449-463
We use long-slit spectroscopic optical data to derive the properties of the extended emitting gas and the nuclear luminosity of a sample of 18 Seyfert 2 galaxies. From the emission-line luminosities and ratios we derive the density, reddening and mass of the ionized gas as a function of distance up to 2–4 kpc from the nucleus. Taking into account the geometric dilution of the nuclear radiation, we derive the radial distribution of covering factors and the minimum rate of ionizing photons emitted by the nuclear source. This number is an order of magnitude larger than that obtained from the rate of ionizing photons 'intercepted' by the gas and measured from the Hα luminosity. A calibration is proposed to recover this number from the observed luminosity. The He ii λ4686/Hβ line ratio was used to calculate the slope of the ionizing spectral energy distribution (SED), which in combination with the number of ionizing photons allows the calculation of the hard X-ray luminosities. These luminosities are consistent with those derived from X-ray spectra in the eight cases for which such data are available and recover the intrinsic X-ray emission in Compton-thick cases. Our method can thus provide reliable estimates of the X-ray fluxes in Seyfert 2 galaxies for the cases where it is not readily available. We also use the ionizing SED and luminosity to predict the infrared luminosity under the assumption that it is dominated by reprocessed radiation from a dusty torus, and find a good agreement with the observed IRAS luminosities. 相似文献
8.
9.
10.
M. Guainazzi F. Fiore G. Matt G.C. Perola 《Monthly notices of the Royal Astronomical Society》2001,327(1):323-328
We have studied the correlation among X-ray absorption, optical reddening and nuclear dust morphology in Seyfert 2 galaxies. Two main conclusions emerge: (i) the Balmer decrement and the amount of X-ray absorption are anticorrelated over a wide range of column density, – the correlation no longer applies to Compton-thick objects , although they span a comparable range in Balmer decrement; (ii) Compton-thin Seyfert 2s seem to prefer nuclear environments, which are rich in dust on scales of hundreds of parsecs. On the other hand, Compton-thick Seyferts indifferently exhibit 'dust-poor' and 'dust-rich' environments. These results support an extension of the Seyfert unification scenario (as recently proposed by Matt ), where Compton-thick Seyfert 2s are observed through compact 'torii', whereas Compton-thin ones are obscured by dust on much larger scales. 相似文献
11.
12.
Until recently, few unequivocal detections had been reported of the hot, X-ray emitting gas thought to be associated with
the large, coherent structures variously described as supershells or superbubbles in dwarf irregular (dIrr) galaxies. In this
contribution we report follow-up XMM-Newton and Chandra observations of our ROSAT detection of X-ray emission associated with the supergiant shell in the nearby dIrr galaxy IC 2574, a member of the M 81
group of galaxies. The spectral properties of the X-ray source suggest that we are dealing with a young (age < 2000 yr) supernova
remnant (SNR). This SNR is most likely one of the many supernovae which have exploded in that region and which have created
the impressive supergiant HI shell.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
14.
S. W. Allen T. Di Matteo A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2000,311(3):493-506
We report the detection of hard X-ray emission components in the spectra of six nearby, giant elliptical galaxies observed with the ASCA satellite. The systems studied, which exhibit strong dynamical evidence for supermassive black holes in their nuclei, are M87, NGC 1399 and NGC 4696 (the dominant galaxies of the Virgo, Fornax and Centaurus clusters, respectively) and NGC 4472, 4636 and 4649 (three further giant ellipticals in the Virgo cluster). The ASCA data for all six sources provide clear evidence for hard emission components, which can be parametrized by power-law models with photon indices in the range Γ=0.6–1.5 (mean value 1.2) and intrinsic 1–10 keV luminosities of 2×1040 –2×1042 erg s−1 . Our results imply the identification of a new class of accreting X-ray source, with X-ray spectra significantly harder than those of binary X-ray sources, Seyfert nuclei or low-luminosity active galactic nuclei, and bolometric luminosities relatively dominated by their X-ray emission. We discuss various possible origins for the hard X-ray emission and argue that it is most likely to be due to accretion on to the central supermassive black holes, via low radiative efficiency accretion flows coupled with strong outflows. In the case of M87, our detected power-law flux is in good agreement with a previously reported measurement from ROSAT High Resolution Imager observations, which were able to resolve the jet from the nuclear X-ray emission components. We confirm previous results showing that the use of multiphase models in the analysis of the ASCA data leads to determinations of approximately solar emission-weighted metallicities for the X-ray gas in the galaxies. We also present results on the individual element abundances in NGC 4636. 相似文献
15.
Andrew M. Read Ian R. Stevens 《Monthly notices of the Royal Astronomical Society》2002,335(1):L36-L40
We present results from XMM–Newton Reflection Grating Spectrometer observations of the prototypical starburst galaxy M82. These high-resolution spectra represent the best X-ray spectra to date of a starburst galaxy. A complex array of lines from species over a wide range of temperatures is seen, the most prominent being due to Lyman α emission from abundant low- Z elements such as N, O, Ne, Mg and Si. Emission lines from helium-like charge states of the same elements are also seen in emission, as are strong lines from the entire Fe L series. Further, the O vii line complex is resolved and is seen to be consistent with gas in collisional ionization equilibrium.
Spectral fitting indicates emission from a large mass of gas with a differential emission measure over a range of temperatures (from ∼ 0.2 to ∼ 1.6 keV, peaking at ∼ 0.7 keV), and evidence for super-solar abundances of several elements is indicated. Spatial analysis of the data indicates that low-energy emission is more extended to the south and east of the nucleus than to the north and west. Higher energy emission is far more centrally concentrated. 相似文献
Spectral fitting indicates emission from a large mass of gas with a differential emission measure over a range of temperatures (from ∼ 0.2 to ∼ 1.6 keV, peaking at ∼ 0.7 keV), and evidence for super-solar abundances of several elements is indicated. Spatial analysis of the data indicates that low-energy emission is more extended to the south and east of the nucleus than to the north and west. Higher energy emission is far more centrally concentrated. 相似文献
16.
Susmita Chakravorty Ajit K. Kembhavi Martin Elvis Gary Ferland 《Monthly notices of the Royal Astronomical Society》2009,393(1):83-98
Signatures of warm absorbers are seen in soft X-ray spectra of about half of all type 1 Seyfert galaxies observed and in some quasars and blazars. We use the thermal equilibrium curve to study the influence of the shape of the ionizing continuum, density and the chemical composition of the absorbing gas on the existence and nature of the warm absorbers. We describe circumstances in which a stable warm absorber can exist as a multiphase medium or one with continuous variation in pressure. In particular, we find the following results: (i) the warm absorber exists only if the spectral index of the X-ray power-law ionizing continuum α > 0.2 and has a multiphase nature if α∼ 0.8 , which interestingly is the spectral index for most of the observed type 1 Seyfert galaxies; (ii) thermal and ionization states of highly dense warm absorbers are sensitive to their density if the ionizing continuum is sufficiently soft, i.e. dominated by the ultraviolet; (iii) absorbing gas with super-solar metallicity is more likely to have a multiphase nature and (iv) the nature of the warm absorber is significantly influenced by the absence of iron and associated elements which are produced in the later stages of star formation history in Type Ia supernovae. 相似文献
17.
18.
Stefan Gottlöber Ewa L. &#;okas Anatoly Klypin Yehuda Hoffman 《Monthly notices of the Royal Astronomical Society》2003,344(3):715-724
Presented here are high spatial and spectral resolution Chandra X-ray observations of the famous interacting galaxy pair, the Mice, a system similar to, though less evolved than, the well-known Antennae galaxies. Previously unpublished ROSAT High Resolution Imager data of the system are also presented.
Starburst-driven galactic winds outflowing along the minor axis of both galaxies (but particularly the northern one) are observed, and spectral and spatial properties, and energetics are presented. That such a phenomenon can occur in such a rapidly evolving and turbulent system is surprising, and this is the first time that the very beginning – the onset, of starburst-driven hot gaseous outflow in a full-blown disc–disc merger has been seen.
Point-source emission is seen at the galaxy nuclei, and within the interaction-induced tidal tails. Further point-source emission is associated with the galactic bar in the southern system. A comparison of the source X-ray luminosity function and of the diffuse emission properties is made with the Antennae and other galaxies, and evidence of a more rapid evolution of the source population than the diffuse component is found. No evidence for variability is found between the Chandra and previous observations. 相似文献
Starburst-driven galactic winds outflowing along the minor axis of both galaxies (but particularly the northern one) are observed, and spectral and spatial properties, and energetics are presented. That such a phenomenon can occur in such a rapidly evolving and turbulent system is surprising, and this is the first time that the very beginning – the onset, of starburst-driven hot gaseous outflow in a full-blown disc–disc merger has been seen.
Point-source emission is seen at the galaxy nuclei, and within the interaction-induced tidal tails. Further point-source emission is associated with the galactic bar in the southern system. A comparison of the source X-ray luminosity function and of the diffuse emission properties is made with the Antennae and other galaxies, and evidence of a more rapid evolution of the source population than the diffuse component is found. No evidence for variability is found between the Chandra and previous observations. 相似文献
19.