120 research outputs found
A view of PKS 2155-304 with XMM-Newton Reflection Grating Spectrometers
We present the high resolution X-ray spectrum of the BL Lac object PKS
2155-304 taken with the RGS units onboard XMM-Newton in November 2000. We
detect a OVII Kalpha resonant absorption line from warm/hot local gas at 21.59A
(~4.5 sigma detection). The line profile is possibly double peaked. We do not
confirm the strong 20.02 A absorption line seen with Chandra and interpreted as
z~0.05 OVIII Kalpha. A 3sigma upper limit of 14 mA on the equivalent width is
set. We also detect the ~23.5 A interstellar OI 1s-->2p line and derive a
factor <=1.5 subsolar O/H ratio in the ISM along PKS 2155-304 line of sight.Comment: 13 pages, 5 figures, 3 tables, emulateapj style. Accepted by Ap
1WGAJ1226.9+3332: a high redshift cluster discovered by Chandra
We report the detection of 1WGAJ1226.9+3332 as an arcminute scale extended
X-ray source with the Chandra X-ray Observatory. The Chandra observation and R
and K band imaging strongly support the identification of 1WGAJ1226.9+3332 as a
high redshift cluster of galaxies, most probably at z=0.85 +- 0.15, with an
inferred temperature kT =10 (+4;-3) keV and an unabsorbed luminosity (in a
r=120" aperture) of 1.3 (+0.16;-0.14) x 1e45 erg/s (0.5-10 keV). This
indication of redshift is also supported by the K and R band imaging, and is in
agreement with the spectroscopic redshift of 0.89 found by Ebeling et al.
(2001). The surface brightness profile is consistent with a beta-model with
beta=0.770 +- 0.025, rc=(18.1 +-0.9)" (corresponding to 101 +- 5 kpc at
z=0.89), and S(0)=1.02 +- 0.08 counts/arcsec**2. 1WGAJ1226.9+3332 was selected
as an extreme X-ray loud source with FX/FV>60; this selection method, thanks to
the large area sampled, seems to be a highly efficient method for finding
luminous high z clusters of galaxies.Comment: 5 pages, 5 figures, 1 table. Accepted for publication in ApJ main
journal. Uses emulateapj.st
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