512 research outputs found
Jet-ISM Interaction in the Radio Galaxy 3C293: Jet-driven Shocks Heat ISM to Power X-ray and Molecular H2 emission
We present a 70ks Chandra observation of the radio galaxy 3C293. This galaxy
belongs to the class of molecular hydrogen emission galaxies (MOHEGs) that have
very luminous emission from warm molecular hydrogen. In radio galaxies, the
molecular gas appears to be heated by jet-driven shocks, but exactly how this
mechanism works is still poorly understood. With Chandra, we observe X-ray
emission from the jets within the host galaxy and along the 100 kpc radio jets.
We model the X-ray spectra of the nucleus, the inner jets, and the X-ray
features along the extended radio jets. Both the nucleus and the inner jets
show evidence of 10^7 K shock-heated gas. The kinetic power of the jets is more
than sufficient to heat the X-ray emitting gas within the host galaxy. The
thermal X-ray and warm H2 luminosities of 3C293 are similar, indicating similar
masses of X-ray hot gas and warm molecular gas. This is consistent with a
picture where both derive from a multiphase, shocked interstellar medium (ISM).
We find that radio-loud MOHEGs that are not brightest cluster galaxies (BCGs),
like 3C293, typically have LH2/LX~1 and MH2/MX~1, whereas MOHEGs that are BCGs
have LH2/LX~0.01 and MH2/MX~0.01. The more massive, virialized, hot atmosphere
in BCGs overwhelms any direct X-ray emission from current jet-ISM interaction.
On the other hand, LH2/LX~1 in the Spiderweb BCG at z=2, which resides in an
unvirialized protocluster and hosts a powerful radio source. Over time, jet-ISM
interaction may contribute to the establishment of a hot atmosphere in BCGs and
other massive elliptical galaxies.Comment: Accepted by ApJ 21 pages in ApJ format, 9 figures, 8 table
Polymorphisms in Immune Response Genes in Infectious Diseases and Autoimmune Diseases
The clinical presentation of infections caused by the same micro-organism is highly
diverse. This is for example demonstrated for infections with Neisseria meningitidis
and respiratory syncytial virus. Some patients infected with N. meningitidis develop
meningitis, while others present with sepsis or even septic shock. Moreover, only part
of the individuals colonized with N. meningitidis develops clinical disease indicating
a different susceptibility between individuals to develop clinical disease. The disease
phenotype in respiratory syncytial virus infection varies from a common cold to severe
bronchiolitis which requires mechanical ventilation.(1) A similar variation is observed
in autoimmune diseases: While some patients with rheumatoid arthritis (RA) have
relatively mild disease, in others joint erosion develops rather early after diagnosis.
Although part of these variations in susceptibility and severity of infection is explained
by, for example, age or crowding, the reasons for this variation are not completely
clear. Genetic heterogeneity is thought to play a role
Large-scale HI in nearby radio galaxies: segregation in neutral gas content with radio source size
We present results of a study of neutral hydrogen (HI) in a complete sample
of nearby non-cluster radio galaxies. We find that radio galaxies with large
amounts of extended HI (M_HI >= 10^9 M_solar) all have a compact radio source.
The host galaxies of the more extended radio sources, all of Fanaroff & Riley
type-I, do not contain these amounts of HI. We discuss several possible
explanations for this segregation. The large-scale HI is mainly distributed in
disk- and ring-like structures with sizes up to 190 kpc and masses up to 2 x
10^10 M_solar. The formation of these structures could be related to past
merger events, although in some cases it may also be consistent with a
cold-accretion scenario.Comment: 4 pages, 2 figures. Accepted for publication in A&A Letters. A
version with full resolution figures can be found at
http://www.astro.rug.nl/~emonts/emonts_HIletter_jan07.pd
Outflows of hot molecular gas in ultra-luminous infra-red galaxies mapped with VLT-SINFONI
We present the detection and morphological characterization of hot molecular
gas outflows in nearby ultra-luminous infrared galaxies, using the near-IR
integral-field spectrograph SINFONI on the VLT. We detect outflows observed in
the 2.12 micron H 1-0 S(1) line for three out of four ULIRGs analyzed;
IRAS 12112+0305, 14348-1447, and 22491-1808. The outflows are mapped on scales
of 0.7-1.6 kpc, show typical outflow velocities of 300-500 km/s, and appear to
originate from the nuclear region. The outflows comprise hot molecular gas
masses of ~6-8x10 M(sun). Assuming a hot-to-cold molecular gas mass ratio
of 6x10, as found in nearby luminous IR galaxies, the total (hot+cold)
molecular gas mass in these outflows is expected to be ~1x10 M(sun). This
translates into molecular mass outflow rates of ~30-85 M(sun)/yr, which is a
factor of a few lower than the star formation rate in these ULIRGs. In
addition, most of the outflowing molecular gas does not reach the escape
velocity of these merger systems, which implies that the bulk of the outflowing
molecular gas is re-distributed within the system and thus remains available
for future star formation. The fastest H outflow is seen in the
Compton-thick AGN of IRAS 14348-1447, reaching a maximum outflow velocity of
~900 km/s. Another ULIRG, IRAS 17208-0014, shows asymmetric H line
profiles different from the outflows seen in the other three ULIRGs. We discuss
several alternative explanations for its line asymmetries, including a very
gentle galactic wind, internal gas dynamics, low-velocity gas outside the disk,
or two superposed gas disks. We do not detect the hot molecular counterpart to
the outflow previously detected in CO(2-1) in IRAS 17208-0014, but we note that
our SINFONI data are not sensitive enough to detect this outflow if it has a
small hot-to-cold molecular gas mass ratio of < 9x10.Comment: Accepted for publication in A&A (11 pages, 10 figures
Localised HI 21-cm absorption towards a double-lobed z=0.24 radio galaxy
We present the results of a mini-survey for associated HI 21-cm absorption at
z < 0.42 with the Giant Metrewave Radio Telescope. Our targets are radio
galaxies, selected on the basis that the 1216 Angstrom luminosities are below
10^23 W/Hz, above which there has never been a detection of 21-cm absorption.
Of the three sources for which we obtained good data, two are unclassified
active galactic nuclei (AGN) and one is type-2. Being a non-detection, the
type-2 object is consistent with our previous result that 21-cm absorption in
radio sources is not dictated by unified schemes of AGN. In the case of the
detection, the absorption only occurs towards one of the two resolved radio
lobes in PKS 1649-062. If the absorption is due to an another intervening
galaxy, or cool HI gas in the intergalactic medium, covering only the
south-west lobe, then, being at the same redshift, this is likely to be
gravitationally bound to the optical object identified as PKS 1649-062. If the
absorption is due to an inclined disk centred between the lobes, intervening
the SW lobe while being located behind the NE lobe, by assuming that it covers
the emission peak at 150 kpc from the nucleus, we estimate a dynamical mass of
~3 x 10^12 solar masses for the disk.Comment: 5 pages accepted by MNRAS Letter
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