1,349 research outputs found
An HI study of three long-tailed irregular galaxies in the cluster Abell1367
We present the results on the distribution and kinematics of H\sc{i} gas
with higher sensitivity and in one case of higher spectral resolution as well
than reported earlier, of three irregular galaxies CGCG 097073, 097079 and
097087 (UGC 06697) in the cluster Abell 1367. These galaxies are known to
exhibit long (5075 kpc) tails of radio continuum and optical emission lines
(H) pointing away from the cluster centre and arcs of starformation on
the opposite sides of the tails. These features as well as the H{\sc i}
properties, with two of the galaxies (CGCG 097073 and 097079) exhibiting
sharper gradients in H{\sc i} intensity on the side of the tails, are
consistent with the H{\sc i} gas being affected by the ram pressure of the
intracluster medium. However the H{\sc i} emission in all the three galaxies
extends to much smaller distances than the radio-continuum and H tails,
and are possibly still bound to the parent galaxies. Approximately 2030 per
cent of the H{\sc i} mass is seen to accumulate on the downstream side due to
the effects of ram pressure.Comment: 19 pages, 19 figures, 3 tables, accepted for publication in the
Bulletin of the Astronomical Society of Indi
HI gas in rejuvenated radio galaxies: GMRT observations of the DDRG J1247+6723
We report the detection of HI absorption towards the inner double of the
double-double radio galaxy (DDRG) J1247+6723 with the Giant Metrewave Radio
Telescope (GMRT). The inner double is a Giga-hertz peaked spectrum (GPS) source
with a linear size of 14 pc while the overall size defined by the outer double
is 1195 kpc, making it a giant radio source. The absorption profile is well
resolved and consists of a number of components on either side of the optical
systemic velocity. The neutral hydrogen column density is estimated to be
N(HI)=6.73*10^{20}(T_s/100)(f_c/1.0) cm^{-2}, where T_s and f_c are the spin
temperature and covering factor of the background source respectively. We
explore any correlation between the occurrence of HI absorption and
rejuvenation of radio activity and suggest that there could be a strong
relationship between them.Comment: 5 pages, 2 figures, accepted for publication in MNRAS Letter
Giant Radio Sources
We present multi-frequency VLA observations of two giant quasars, 0437-244
and 1025-229, from the Molonglo Complete Sample. These sources have
well-defined FRII radio structure, possible one-sided jets, no significant
depolarization between 1365 and 4935 MHz and low rotation measure (). The giant sources are defined to be those whose overall
projected size is 1 Mpc. We have compiled a sample of about 50 known
giant radio sources from the literature, and have compared some of their
properties with a complete sample of 3CR radio sources of smaller sizes to
investigate the evolution of giant sources, and test their consistency with the
unified scheme for radio galaxies and quasars. We find an inverse correlation
between the degree of core prominence and total radio luminosity, and show that
the giant radio sources have similar core strengths to the smaller sources of
similar total luminosity. Hence their large sizes are unlikely to be due to
stronger nuclear activity. The degree of collinearity of the giant sources is
also similar to the sample of smaller sources. The luminosity-size diagram
shows that the giant sources are less luminous than our sample of smaller-sized
3CR sources, consistent with evolutionary scenarios where the giants have
evolved from the smaller sources losing energy as they expand to these large
dimensions. For the smaller sources, radiative losses due to synchrotron
radiation is more significant while for the giant sources the equipartition
magnetic fields are smaller and inverse Compton losses with the microwave
background radiation is the dominant process. The radio properties of the giant
radio galaxies and quasars are consistent with the unified scheme.Comment: 14 pages with 12 figures, MNRAS LaTex. Accepted for publication in
MNRAS. Minor changes in the text and couple of references adde
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