arXiv subjects

S. J. Xue

Publications and source records attributed to S. J. Xue.

3 recordsLinked to original sources

arXiv2004

Chandra Observations of ULIRGs: Extended Hot Gas Halos in Merging Galaxies

We study the properties of hot gaseous halos in 10 nearby ultraluminous IRAS galaxies observed with the ACIS instrument on board Chandra. For all sample galaxies, diffuse soft X-ray emissions are found within ~10 kpc of the central region; their spectra are well fitted by a MEKAL model plus emission lines from alpha-elements and other ions. The temperature of the hot gas is about 0.7 keV and metallicity is about 1 solar. Outside the central region, extended hot gaseous halos are found for nine out of the ten ULIRGs. Most spectra of these extended halos can be fitted with a MEKAL model with a temperature of about 0.6 keV and a low metallicity (~ 0.1 solar). We discuss the implications of our results on the origin of X-ray halos in elliptical galaxies and the feedback processes associated with starbursts.

astro-ph↗

arXiv2002

The nature of ultra-luminous X-ray sources in NGC4565

We report the optical identifications of two X-ray luminous point sources in the spiral galaxy NGC4565 based on archive data of Chandra and the Hubble Space Telescope. The central X-ray point source, RXJ1236.3+2559, is found to be the nucleus of NGC4565 with an X-ray luminosity of Lx= 4.3 10^{39} erg. We show that its multi-waveband properties are consistent with it being a low-luminosity active galactic nucleus. A faint optical counterpart with B=25.1 and I=24.0 was identified for the off-nucleus X-ray point source, RXJ1236.2+2558. Its extinction corrected B magnitude is estimated to be 24.5. The X-ray to optical flux ratio (fx/fB) is about 540. From the optical and X-ray properties we argue that RXJ1236.2+2558 is an ultra-luminous X-ray compact source with Lx=6.5 10^{39} erg. The source is probably located in a faint globular cluster at the outer edge of NGC4565's bulge.

astro-ph↗

arXiv2001

Chandra Observations of MRK 273: Unveiling the Central AGN and the Extended Hot Gas Halo

We report X-ray observations of the field containing the ultraluminous IRAS galaxy Mrk~273 Using the ACIS-S3 instrument on board Chandra. The high resolution X-ray image, for the first time, reveals a compact hard X-ray nucleus in Mrk~273. Its X-ray energy distribution is well described by a heavily obscured power-law spectrum plus a narrow $\Feka$ emission line at 6.4 keV. The neutral hydrogen column density is about $4\times10^{23}\cm^{-2}$, implying an absorption -corrected X-ray luminosity (0.1--10 keV) for the nucleus of $\Lx\approx 6.5\times 10^{43} \ergs$. There are also bright soft X-ray clumps and diffuse soft X-ray emissions surrounding the central hard X-ray nucleus within the $10\arcsec$ of the nuclear region. Its spectrum can be fitted by a MEKAL thermal model with temperature of about 0.8 keV and high metallicity ($Z\sim 1.5Z_\odot$) plus emission lines from $α$ elements and ions. Further outside the central region, the Chandra observations reveal a very extended hot gas halo with a projected diameter of about $108 \kpc\times 68 \kpc$ and soft X-ray luminosity of $\Lx\approx 1.9\times 10^{41} \ergs$. The temperature of the hot gas is about 0.62 keV with a low metallicity ($Z \sim 0.1 Z_\odot$). We discuss the nature of the AGN in Mrk~273 and the implications of our results on the origin of X-ray halos in elliptical galaxies. We also discuss the properties of Mrk~273x, a background AGN in the Mrk~273 field. The AGN has an X-ray luminosity of $\Lx \approx 2.43\times 10^{44}\ergs$ in the 0.5-10 keV band. Its X-ray properties resemble those of Seyfert 1 galaxies while its optical properties are similar to Seyfert 2 galaxies. Such mixed classifications may be a challenge for the unification scheme of AGNs.

astro-ph↗