1,269 research outputs found
A cluster pair : A3532 and A3530
We present a detailed study of a close pair of clusters of galaxies, A3532
and A3530, and their environments. The \textit{Chandra} X-ray image of A3532
reveals presence of substructures on scales of 20 in its
core. XMM-Newton maps of the clusters show excess X-ray emission from an
overlapping region between them. Spectrally determined projected temperature
and entropy maps do not show any signs of cluster scale mergers either in the
overlapping region or in any of the clusters. In A3532, however, some signs of
the presence of galaxy scale mergers are visible e.g., anisotropic temperature
variations in the projected thermodynamic maps, a wide angled tailed (WAT)
radio source in the brighter nucleus of its dumbbell Brightest Cluster Galaxy
(BCG), and a candidate X-ray cavity coincident with the northwestern extension
of the WAT source in the low-frequency radio observations. The northwestern
extension in A3532 seems either a part of the WAT or an unrelated diffuse
source in A3532 or in the background. There is an indication that the cool core
in A3532 has been disrupted by the central AGN activity. A reanalysis of the
redshift data reinforces the close proximity of the clusters. The excess
emission in the overlapping region appears to be a result of tidal interactions
as the two clusters approach each other for the first time. However, we can not
rule out the possibility of the excess being due to the chance superposition of
their X-ray halos.Comment: Accepted for publication in the Astrophysical Journa
Wild edible plants of Jharkhand and their utilitarian perspectives
237-250The wild edible plants (WEPs) form an important constituent of traditional diets of the tribal community of Jharkhand. Most of the rural populations residing in different parts of Jharkhand depend on plants and their parts to fulfil their daily needs and have developed unique knowledge about their utilization. The present study has been conducted to document the indigenous knowledge related to the diversity and uses of wild edible weeds in day to day life of tribal in Jharkhand. A total of 77 different herbs, shrubs, and small trees have been recorded belonging to 38 families of which 73 are edible either as a vegetable or as medicine or in both forms directly or after proper processing. The common wild edible herbs frequently distributed in the study area are Hemidesmus indicus R. Br. (51 quadrats out of 134) and Cynodon dactylon (L.) Pers. (47 quadrats out of 134). Similarly, the most frequent edible shrubs are Clerodendrum viscosum Vent., nom. superfl. (40), Lantana camara L. (35), Croton oblongifolius Roxb. (34) and Flemingia stobilifera (L.) R.Br. (20). The diversity of WEPs in Jharkhand has found to be depleted due to their over exploitation and unsustainable harvesting for foods, medicines as well as because of various other biotic interferences including grazing, herbivory and anthropogenic fire. Therefore, there is an urgent need to conserve these valuable Wild edible plants (WEPs) and use it in a sustainable manner to ensure future demand. Besides, further research is also warrant to explore the therapeutic potentials as well the nutritive values of WEPs, so that, it can give a scientific basis for the further development of herbal drugs and traditional foods
Detecting cold gas at intermediate redshifts: GMRT survey using Mg II systems
Intervening HI 21-cm absorption systems at z > 1.0 are very rare and only 4
confirmed detections have been reported in the literature. Despite their
scarcity, they provide interesting and unique insights into the physical
conditions in the interstellar medium of high-z galaxies. Moreover, they can
provide independent constraints on the variation of fundamental constants. We
report 3 new detections based on our ongoing Giant Metrewave Radio Telescope
(GMRT) survey for 21-cm absorbers at 1.10< z_abs< 1.45 from candidate damped
Lyman_alpha systems. The 21-cm lines are narrow for the z_abs = 1.3710 system
towards SDSS J0108-0037 and z_abs = 1.1726 system toward SDSS J2358-1020. Based
on line full-width at half maximum, the kinetic temperatures are <= 5200 K and
<=800 K, respectively. The 21-cm absorption profile of the third system, z_abs
=1.1908 system towards SDSS J0804+3012, is shallow, broad and complex,
extending up to 100 km/s. The centroids of the 21-cm lines are found to be
shifted with respect to the corresponding centroids of the metal lines derived
from SDSS spectra. This may mean that the 21-cm absorption is not associated
with the strongest metal line component.Comment: 13 pages with 5 figures. Accepted for publication in ApJ
Tale of J1328+2752 : a misaligned double-double radio galaxy hosted by a binary black-hole?
We present a radio and optical study of the double-double radio galaxy J1328+2752 based on new low-frequency Giant Metrewave Radio Telescope observations and Sloan Digital Sky Survey (SDSS) data. The radio data were used to investigate the morphology and to perform a spectral index analysis. In this source, we find that the inner double is misaligned by similar to 30 degrees from the axis of the outer diffuse structure. The SDSS spectrum shows that the central component has double-peaked line profiles with different emission strengths. The average velocity offset of the two components is 235 +/- 10.5 kms(-1). The misaligned radio morphology along with the double-peaked emission lines indicate that this source is a potential candidate binary supermassive black hole. This study further supports mergers as a possible explanation for repeated jet activity in radio sources
Compact steep-spectrum sources from the S4 sample
We present the results of 5-GHz observations with the VLA A-array of a sample
of candidate Compact Steep Spectrum sources (CSSs) selected from the S4 survey.
We also estimate the symmetry parameters of high-luminosity CSSs selected from
different samples of radio sources, and compare these with the larger sources
of similar luminosity to understand their evolution and the consistency of the
CSSs with the unified scheme for radio galaxies and quasars. The majority of
CSSs are likely to be young sources advancing outwards through a dense
asymmetric environment. The radio properties of CSSs are found to be consistent
with the unified scheme, in which the axes of the quasars are observed close to
the line of sight, while radio galaxies are observed close to the plane of the
sky.Comment: accepted for publication in mnras; 8 pages, figure 1 with 21 images,
and two additional figures; 2 table
Dispersionless motion in a driven periodic potential
Recently, dispersionless (coherent) motion of (noninteracting) massive
Brownian particles, at intermediate time scales, was reported in a sinusoidal
potential with a constant tilt. The coherent motion persists for a finite
length of time before the motion becomes diffusive. We show that such coherent
motion can be obtained repeatedly by applying an external zero-mean square-wave
drive of appropriate period and amplitude, instead of a constant tilt. Thus,
the cumulative duration of coherent motion of particles is prolonged. Moreover,
by taking an appropriate combination of periods of the external field, one can
postpone the beginning of the coherent motion and can even have coherent motion
at a lower value of position dispersion than in the constant tilt case.Comment: 4 pages, 4 figure
Contact Pressure Distribution on Subgrade Soil Underlying Geocell Reinforced Foundation Beds
© Copyright © 2019 Dash, Saikia and Nimbalkar. High contact stresses generated in the foundation soil, owing to increased load, causes distress, instability, and large settlements. Present days, geocell reinforcement is being widely used for the performance improvement of foundation beds. Pressure distribution on subgrade soil in geocell reinforced foundation beds is studied through model tests and numerical analysis. The test data indicates that with provision of geocell reinforcement the contact pressure on the subgrade soil reduces significantly. Consequently, the subgrade soil tends to remain intact until large loadings on the foundation leading to significant performance improvement. Through numerical analysis it is observed that the geocells in the region under the footing were subjected to compression and beyond were in tension. This indicates that the geocell reinforcement right under the footing directly sustains the footing loading through mobilization of its compressive stiffness and bending rigidity. Whereas, the end portions of the geocell reinforcement, contribute to the performance improvement in a secondary manner through mobilization of anchorage derived from soil passive resistance and friction
Relativistic and slowing down: the flow in the hotspots of powerful radio galaxies and quasars
Pairs of radio emitting jets with lengths up to several hundred kiloparsecs
emanate from the central region (the `core') of radio loud active galaxies.
In the most powerful of them, these jets terminate in the `hotspots', compact
high brightness regions, where the jet flow collides with the intergalactic
medium (IGM). Although it has long been established that in their inner
(parsec) regions these jet flows are relativistic, it is still not clear
if they remain so at their largest (hundreds of kiloparsec) scales. We argue
that the X-ray, optical and radio data of the hotspots, despite their
at-first-sight disparate properties, can be unified in a scheme involving a
relativistic flow upstream of the hotspot that decelerates to the
sub-relativistic speed of its inferred advance through the IGM and viewed at
different angles to its direction of motion. This scheme, besides providing an
account of the hotspot spectral properties with jet orientation, it also
suggests that the large-scale jets remain relativistic all the way to the
hotspots.Comment: to appear in ApJ
Discovery of a red quasar with recurrent activity
We report a new double-double radio quasar, DDRQ, J07464526 which exhibits
two cycles of episodic activity. From radio continuum observations at 607 MHz
using the GMRT and 1400 MHz from the FIRST survey we confirm its episodic
nature. We examine the SDSS optical spectrum and estimate the black hole mass
to be (8.20.3)10M from its observed MgII emission
line, and the Eddington ratio to be 0.03. The black hole mass is significantly
smaller than for the other reported DDRQ, J0935+0204, while the Eddington
ratios are comparable. The SDSS spectrum is significantly red continuum
dominated suggesting that it is highly obscured with
mag. This high obscuration further indicates the
existence of a large quantity of dust and gas along the line of sight, which
may have a key role in triggering the recurrent jet activity in such objects.Comment: 5 pages, 3 figures, 1 table. Accepted for publication in Ap
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