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Register a new userProbable detection of HI at $zsimeq 1.3$ from DEEP2 galaxies using the GMRT
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We have observed the DEEP2 galaxies using the Giant Meterwave Radio Telescope in the frequency band of 610 MHz. There are $simeq 400$ galaxies in the redshift range $1.24 < z < 1.36$ and within the field of view $simeq 44$, of the GMRT dishes. We have coadded the HI 21 cm-line emissions at the locations of these DEEP2 galaxies. We apply stacking on three different data cubes: primary beam uncorrected, primary beam corrected (uniform weighing ) and primary beam corrected (optimal weighing). We obtain a peak signal strength in the range $8hbox{--}25 , rm mu$Jy/beam for a velocity width in the range $270hbox{--} 810 , rm km , sec^{-1}$. The error on the signal, computed by bootstrapping, lies in the range $2.5hbox{--}6 , rm mu$Jy/beam, implying a 2.5--4.7-$sigma$ detection of the signal at $z simeq 1.3$. We compare our results with N-body simulations of the signal at $zsimeq 1$ and find reasonable agreement. We also discuss the impact of residual continuum and systematics.
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We present HI observations of four giant low surface brightness (GLSB) galaxies UGC 1378, UGC 1922, UGC 4422 and UM 163 using the Giant Meterwave Radio Telescope (GMRT). We include HI results on UGC 2936, UGC 6614 and Malin 2 from literature. HI is detected from all the galaxies and the extent is roughly twice the optical size; in UM 163, HI is detected along a broken disk encircling the optical galaxy. We combine our results with those in literature to further understand these systems. The main results are the following: (1) The peak HI surface densities in GLSB galaxies are several times 10^21 cm^{-2} . The HI mass is between 0.3 - 4 x 10^10 M_Sun/yr, dynamical mass ranges from a few times 10^11 M_Sun/yr to a few times 10^12 M_Sun/yr. (2) The rotation curves of GLSB galaxies are flat to the outermost measured point with rotation velocities of the seven GLSB galaxies being between 225 and 432 km s^{-1}. (3) Recent star formation traced by near-ultraviolet emission in five GLSB galaxies in our sample appears to be located in rings around the galaxy centre. We suggest that this could be due to a stochastic burst of star formation at one location in the galaxy being propagated along a ring over a rotation period. (4) The Hi is correlated with recent star formation in five of the seven GLSB galaxies.
The GMRT HI 21cm-line observations of galaxies in the Eridanus group are presented. The Eridanus group, at a distance of ~23 Mpc, is a loose group of ~200 galaxies. The group extends more than 10 Mpc in projection. The velocity dispersion of the galaxies in the group is ~240 km/s. The galaxies are clustered into different sub-groups. The overall population mix of the group is 30% (E+S0) and 70% (Sp+Irr). The observations of 57 Eridanus galaxies were carried out with the GMRT for ~200 hour. HI emission was detected from 31 galaxies. The channel rms of ~1.0 mJy beam^{-1} was achieved for most of the image-cubes made with 4 hour of data. The corresponding HI column density sensitivity (3-sigma) is ~1x10^{20} cm^{-2} for a velocity-width of ~13.4 km/s. The 3-sigma detection limit of HI mass is ~1.2x10^{7} M_sun for a line-width of 50 km/s. Total HI images, HI velocity fields, global HI line profiles, HI mass surface densities, HI disk parameters and HI rotation curves are presented. The velocity fields are analysed separately for the approaching and the receding sides of the galaxies. This data will be used to study the HI and the radio continuum properties, the Tully-Fisher relations, the dark matter halos, and the kinematical and HI lopsidedness in galaxies.
Comets are the most primordial objects in our solar system which are made of icy bodies. Comets used to release gas and dust when it moves close to the Sun. The C/2020 F3 (NEOWISE) is a large periodic comet that is moving in a near-parabolic orbit. The C/2020 F3 (NEOWISE) is the brightest comet in the northern hemisphere after comet Hale-Bopp in 1997. Here we present the first interferometric high-resolution detection of the comet C/2020 F3 (NEOWISE) using the Giant Metrewave Radio Telescope (GMRT). The observational frequency range is 1050$-$1450 MHz. We detect the radio continuum emission from this comet with flux density level 2.8$-$3.4 mJy between the frequency range 1050--1450 MHz. We also detect atomic HI absorption line at $ u$ = 1420 MHz ($sim$5$sigma$ significance) with column density $N(textrm {HI}) = (1.8 pm 0.09)times 10^{22}$ cm$^{-2}$. The continuum emission from the comet in meter wavelength arises from the large Icy Grains Halo (IGH) region. Significant detection of C/2020 F3 in $sim$21 cm indicates the presence of large size of particles in the coma region of the comet.
We confirm the detection of 3 groups in the Lynx supercluster, at z~1.3, and give their redshifts and masses. We study the properties of the group galaxies as compared to the central clusters, RXJ0849+4452 and RXJ0848+4453, selecting 89 galaxies in the clusters and 74 galaxies in the groups. We morphologically classify galaxies by visual inspection, noting that our early-type galaxy (ETG) sample would have been contaminated at the 30% -40% level by simple automated classification methods (e.g. based on Sersic index). In luminosity selected samples, both clusters and groups show high fractions of Sa galaxies. The ETG fractions never rise above ~50% in the clusters, which is low compared to the fractions observed in clusters at z~1. However, ETG plus Sa fractions are similar to those observed for ETGs in clusters at z~1. Bulge-dominated galaxies visually classified as Sas might also be ETGs with tidal features or merger remnants. They are mainly red and passive, and span a large range in luminosity. Their star formation seems to have been quenched before experiencing a morphological transformation. Because their fraction is smaller at lower redshifts, they might be the spiral population that evolves into ETGs. For mass-selected samples, the ETG fraction show no significant evolution with respect to local clusters, suggesting that morphological transformations occur at lower masses and densities. The ETG mass-size relation shows evolution towards smaller sizes at higher redshift in both clusters and groups, while the late-type mass-size relation matches that observed locally. The group ETG red sequence shows lower zero points and larger scatters than in clusters, both expected to be an indication of a younger galaxy population. The estimated age difference is small when compared to the difference in age at different galaxy masses.
We present 279 galaxy cluster candidates at $z > 1.3$ selected from the 94 deg$^{2}$ Spitzer South Pole Telescope Deep Field (SSDF) survey. We use a simple algorithm to select candidate high-redshift clusters of galaxies based on Spitzer/IRAC mid-infrared data combined with shallow all-sky optical data. We identify distant cluster candidates in SSDF adopting an overdensity threshold that results in a high purity (80%) cluster sample based on tests in the Spitzer Deep, Wide-Field Survey of the Bootes field. Our simple algorithm detects all three $1.4 < z leq 1.75$ X-ray detected clusters in the Bootes field. The uniqueness of the SSDF survey resides not just in its area, one of the largest contiguous extragalactic fields observed with Spitzer, but also in its deep, multi-wavelength coverage by the South Pole Telescope (SPT), Herschel/SPIRE and XMM-Newton. This rich dataset will allow direct or stacked measurements of Sunyaev-Zeldovich effect decrements or X-ray masses for many of the SSDF clusters presented here, and enable systematic study of the most distant clusters on an unprecedented scale. We measure the angular correlation function of our sample and find that these candidates show strong clustering. Employing the COSMOS/UltraVista photometric catalog in order to infer the redshift distribution of our cluster selection, we find that these clusters have a comoving number density $n_c = (0.7^{+6.3}_{-0.6}) times 10^{-7} h^{3} mathrm{Mpc}^{-3}$ and a spatial clustering correlation scale length $r_0 = (32 pm 7) h^{-1} rm{Mpc}$. Assuming our sample is comprised of dark matter halos above a characteristic minimum mass, $M_{{rm min}}$, we derive that at $z=1.5$ these clusters reside in halos larger than $M_{{rm min}} = 1.5^{+0.9}_{-0.7} times 10^{14} h^{-1} M_{odot}$. (abridged)
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