In this paper we present a wide-area 610 MHz survey of the ELAIS\,N1 field with the GMRT, covering an area of 12.8 deg$^2$ at a resolution of 6 arcsec and with an rms noise of $\sim 40$ $μ$Jy beam$^{-1}$. This is equivalent to $\sim 20$ $μ$Jy beam$^{-1}$ rms noise at 1.4 GHz for a spectral index of $-0.75$. The primary goal of the survey was to study the polarised sky at sub-mJy flux densities at $<$ GHz frequencies. In addition, a range of other science goals, such as investigations in to the nature of the low-frequency $μ$Jy source populations and alignments of radio jets. A total of 6,400 sources were found in this region, the vast majority of them compact. The sample jointly detected by GMRT at 610 MHz and by VLA FIRST at 1.4\,GHz has a median spectral index of $-0.85 \pm 0.05$ and a median 610 MHz flux density of 4.5 mJy. This region has a wealth of ancillary data which is useful to characterize the detected sources. The multi-wavelength cross matching resulted optical/IR counterparts to $\sim 90$ per~cent of the radio sources, with a significant fraction having at least photometric redshift. Due to the improved sensitivity of this survey over preceding ones, we have discovered six giant radio sources (GRS), with three of them at $z \sim 1$ or higher. This implies that the population of GRS may be more abundant and common than known to date and if true this has implications for the luminosity function and the evolution of radio sources. We have also identified several candidate extended relic sources.
This is the first of a series of papers based on sensitive 610 MHz observations of the ELAIS N1 field using the Giant Metrewave Radio Telescope. We describe the observations, processing and source catalogue extraction from a deep image with area of 1.86\,deg$^{2}$ and minimum noise of $\sim$7.1\,$μ$Jy/beam. We compile a catalogue of 4290 sources with flux densities in the range 28.9\,$μ$Jy - 0.503\,Jy, and derive the Euclidean-normalized differential source counts for sources with flux densities brighter than $\rm{35.5\,μ\,Jy}$. Our counts show a flattening at 610 MHz flux densities below 1 mJ…
We report the discovery of a remnant radio AGN J1615+5452 in the field of ELAIS-N1. GMRT continuum observations at 150, 325 and 610 MHz combined with archival data from the 1.4 GHz NVSS survey were used to derive the radio spectrum of the source. At a redshift $z \sim$ 0.33, J1615+5452 has a linear size of $\sim$ 100 kpc and spectral indices ranging between $α^{1400}_{610} < -1.5$ and $α^{325}_{150} = -0.61 \pm 0.12$. While the source has a diffuse radio emission at low frequencies, we do not find evidence of core, jets or hotspots in the 1.4\,GHz VLA data of $\sim 5$ arcsec angular resolution…
We report on the discovery of three new pulsars in the first blind survey of the north Galactic plane (45 degrees < l < 135 degrees; |b| < 1 degrees with the Giant Meterwave Radio telescope (GMRT) at an intermediate frequency of 610 MHz. The survey covered 106 square degrees with a sensitivity of roughly 1 mJy to long-period pulsars (pulsars with period longer than 1 s). The three new pulsars have periods of 318, 933, and 1056 ms. Their timing parameters and flux densities, obtained in follow up observations with the Lovell Telescope at Jodrell Bank and the GMRT, are presented. We also report …
The GMRT has been used to make deep, wide-field surveys of several fields at 610 MHz, with a resolution of about 5 arcsec. These include the Spitzer Extragalactic First Look Survey field, where 4 square degrees were observed with a r.m.s. sensitivity of about 30 microJy/beam, and several SWIRE fields (namely the Lockman Hole, ELAIS-N1 and N2 fields) covering more than 20 square degrees with a sensitivity of about 80 microJy beam or better. The analysis of these observations, and some of the science results are described.
We study the cosmic evolution of radio sources out to $z \simeq 1.5$ using a GMRT 610 MHz survey covering $\sim$1.86 deg$^2$ of the ELAIS N1 field with a minimum/median rms noise 7.1/19.5\,$μ$Jy / beam and an angular resolution of 6\,arcsec. We classify sources as star forming galaxies (SFGs), radio-quiet (RQ) and radio-loud (RL) Active Galactic Nuclei (AGN) using a combination of multi-wavelength diagnostics and find evidence in support of the radio emission in SFGs and RQ AGN arising from star formation, rather than AGN-related processes. At high luminosities, however, both SFGs and RQ AGN d…
We report Giant Meterwave Radio Telescope (GMRT) continuum observations of six nearby normal galaxies at 333 MHz. The galaxies are observed with angular resolutions better than ~20" (corresponding to a linear scale of about 0.4 - 1 kpc). These observations are sensitive to all the angular scales of interest, since the resolution of the shortest baseline in GMRT is greater than the angular size of the galaxies. Further, for five of these galaxies we show that at 333 MHz, the mean thermal fraction is less than 5%. Using archival data at about 1 GHz, we estimate the mean thermal fraction to be ab…
In this first paper of the series, we present initial results of newly upgraded Giant Meterwave Radio Telescope (uGMRT) observation of European Large-Area ISO Survey-North 1 (ELAIS-N1) at 325 MHz with 32 MHz bandwidth. Precise measurement of fluctuations in Galactic and extragalactic foreground emission as a function of frequency as well as angular scale is necessary for detecting redshifted 21-cm signal of neutral hydrogen from Cosmic Dawn, Epoch of Reionization (EoR) and post-reionization epoch. Here, for the first time we have statistically quantified the Galactic and extragalactic foregrou…
We present an extension of our search for Extremely Inverted Spectrum Extragalactic Radio Sources (EISERS) to the northern celestial hemisphere. With an inverted radio spectrum of slope $α$ > +2.5, these rare sources would either require a non-standard particle acceleration mechanism (in the framework of synchrotron self-absorption hypothesis), or a severe free-free absorption which attenuates practically all of their synchrotron radiation at metre wavelengths. By applying a sequence of selection filters, a list of 15 EISERS candidates is extracted out by comparing two large-sky radio surveys,…
We present the 25 square-degree GMRT-XXL-N 610 MHz radio continuum survey, conducted at 50~cm wavelength with the Giant Metrewave Radio Telescope (GMRT) towards the XXL Northern field (XXL-N). We combined previously published observations of the XMM-Large Scale Structure (XMM-LSS) field, located in the central part of XXL-N, with newly conducted observations towards the remaining XXL-N area, and imaged the combined data-set using the Source Peeling and Atmospheric Modeling ({\sc SPAM}) pipeline. The final mosaic encompasses a total area of $30.4$ square degrees, with ${\rm rms}<150~μ$Jy/beam o…
We report the discovery of a fourth eastern arc (Arc E) towards the cool-core cluster Abell 2626 using 610 MHz Giant Metrewave Radio Telescope observations. Three arcs towards north, west and south were known from earlier works at 1400 MHz and proposed to have originated in precessing radio jets of the central active galactic nucleus. The 610 - 1400 MHz integrated spectral indices of the arcs are in the range 3.2 - 3.6 and the spectral index map shows uniform distribution along the lengths of the arcs. If associated with A2626, the arcs have linear extents in the range 79 - 152 kpc. The detect…
We present observations of three active sites of star formation in the Taurus Molecular Cloud complex taken at 323 and 608 MHz (90 and 50 cm, respectively) with the Giant Metrewave Radio Telescope (GMRT). Three pointings were observed as part of a pathfinder project, targeted at the young stellar objects (YSOs) L1551 IRS 5, T Tau and DG Tau (the results for these target sources were presented in a previous paper). In this paper, we search for other YSOs and present a survey comprising of all three fields; a by-product of the large instantaneous field of view of the GMRT. The resolution of the …
We present 610-MHz Giant Metrewave Radio Telescope observations of 0.84 deg$^2$ of the AMI001 field (centred on $00^{\rm h} 23^{\rm m} 10^{\rm s}$, $+31^{\circ} 53'$) with an r.m.s. noise of 18 $μ$Jy beam$^{-1}$ in the centre of the field. 955 sources are detected, and 814 are included in the source count analysis. The source counts from these observations are consistent with previous work. We have used these data to study the spectral index distribution of a sample of sources selected at 15.7 GHz from the recent deep extension to the Tenth Cambridge (10C) survey. The median spectral index, $α…
The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ~10 microJy/bm over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, the deepest of the LoTSS deep fields to date. With an effective observing time of 163.7 hours, it reaches a root mean square (RMS) noise level below 20 microJy/bm in the central region (and below 30 microJy/bm over 10 square degrees). The resolution is 6 arcsecs and 84862 radio sources were detected …
We present a study of the distribution of radio jet position angles of radio galaxies over an area of 1 square degree in the ELAIS N1 field. ELAIS N1 was observed with the Giant Metrewave Radio Telescope at 612 MHz to an rms noise level of 10 $μ$Jy and angular resolution of $6"\times 5"$. The image contains 65 resolved radio galaxy jets. The spatial distribution reveals a prominent alignment of jet position angles along a "filament" of about 1$^{\circ}$. We examine the possibility that the apparent alignment arises from an underlying random distribution and find that the probability of chance …
We present Giant Metrewave Radio Telescope (GMRT) 323 MHz radio continuum observations toward 13 radio-loud quasars at $z>5$, sampling the low-frequency synchrotron emission from these objects. Among the 12 targets successfully observed, we detected 10 above $4σ$ significance, while 2 remain undetected. All of the detected sources appear as point sources. Combined with previous radio continuum detections from the literature, 9 quasars have power-law spectral energy distributions throughout the radio range; for some the flux density drops with increasing frequency while it increases for others.…
We present high-resolution, high-sensitivity radio continuum observations of the nearby spiral galaxy NGC 2997 at 332, 616 and 1272 MHz using the Giant Metrewave Radio Telescope (GMRT). The integrated spectrum of this galaxy has a spectral index of -0.92 ($S_ν\proptoν^α$) and we place an upper limit to the thermal fraction at 1272 MHz of ~ 10 per cent. Our multi-frequency study shows a relatively flat spectrum source ($α$ ~ -0.6) at the centre of the galaxy. This leads to radio detection of a circumnuclear ring in the high resolution map at 1272 MHz. We detect five hotspots in the ring, with a…
We report continuum GMRT observations aimed to explore the behavior of the jet associated with IRAS 16547-4247 at very low frequencies (325 MHz and 610 MHz). The obtained maps reveal an elongated morphology in the SE-NW direction. In addition, the 610 MHz map shows three knots associated to the elongated morphology that seems to correspond to the triple radio source identified as the jet seen at higher frequencies. However, at 325 MHz, although an elongated morphology is also observed, only two knots appear in the map. By comparing our knot positions at both frequencies with a precessing jet m…
We report low frequency observations of Wolf-Rayet galaxies, NGC 4214 and NGC 4449 at 610, 325 and 150 MHz, using the Giant Meterwave Radio Telescope (GMRT). We detect diffuse extended emission from NGC 4214 at and NGC 4449. NGC 4449 is observed to be five times more radio luminous than NGC 4214, indicating vigorous star formation. We estimate synchrotron spectral index after separating the thermal free-free emission and obtain $α_{nt}=-0.63\pm0.04$ (S$\proptoν^{α_{nt}}$) for NGC 4214 and $-0.49\pm0.02$ for NGC 4449. About $22\%$ of the total radio emission from NGC 4214 and $\sim 9\%$ from NG…
We probe the relationship between star formation rate (SFR) and radio synchrotron luminosity in galaxies at 0 < z < 2 within the northern Spitzer Wide-area Infrared Extragalactic survey (SWIRE) fields, in order to investigate some of the assumptions that go into calculating the star formation history of the Universe from deep radio observations. We present new 610-MHz Giant Metrewave Radio Telescope (GMRT) observations of the European Large-Area ISO Survey (ELAIS)-N2 field, and using this data, along with previous GMRT surveys carried out in the ELAIS-N1 and Lockman Hole regions, we construct …
We present the results of 325 MHz GMRT observations of a super-cluster field, known to contain five Abell clusters at redshift $z \sim 0.2$. We achieve a nominal sensitivity of $34\,μ$Jy beam$^{-1}$ toward the phase centre. We compile a catalogue of 3257 sources with flux densities in the range $183\,μ\rm{Jy}\,-\,1.5\,\rm{Jy}$ within the entire $\sim 6.5$ square degree field of view. Subsequently, we use available survey data at other frequencies to derive the spectral index distribution for a sub-sample of these sources, recovering two distinct populations -- a dominant population which exhib…
Low frequency observations at 325 and 610 MHz have been carried out for two "radio-loud" Seyfert galaxies, NGC4235 and NGC4594 (Sombrero galaxy), using the Giant Meterwave Radio Telescope (GMRT). The 610 MHz total intensity and 325-610 MHz spectral index images of NGC4235 tentatively suggest the presence of a "relic" radio lobe, most likely from a previous episode of AGN activity. This makes NGC4235 only the second known Seyfert galaxy after Mrk6 to show signatures of episodic activity. Spitzer and Herschel infrared spectral energy distribution (SED) modelling using the clumpyDREAM code predic…
We study the space density evolution of active galactic nuclei (AGN) using the $610 \ \mathrm{MHz}$ radio survey of the XXL-North field, performed with the Giant Metrewave Radio Telescope (GMRT). The survey covers an area of $30.4 \ \mathrm{deg}^2$, with a beamsize of $6.5 \ \mathrm{arcsec}$. The survey is divided into two parts, one covering an area of $11.9 \ \mathrm{deg}^2$ with $1 σ$ rms noise of $200\ \mathrm{μJy \ beam^{-1}}$ and the other spanning $18.5 \ \mathrm{deg}^2$ with rms noise of $45\ \mathrm{μJy \ beam^{-1}}$. We extracted the catalog of radio components above $7 σ$. The catal…
Using the Giant Metrewave Radio Telescope (GMRT) we performed deep observations to search for radio pulsations in the directions of unidentified Fermi Large Area Telescope (LAT) gamma-ray sources. We report the discovery of an eclipsing black-widow millisecond pulsar, PSR J1544+4937, identified with the un-cataloged gamma-ray source Fermi J1544.2+4941. This 2.16 ms pulsar is in a 2.9 hours compact circular orbit with a very low-mass companion (Mc > 0.017 Msun). At 322 MHz this pulsar is found to be eclipsing for 13% of its orbit, whereas at 607 MHz the pulsar is detected throughout the low-fre…
We have used the upgraded Giant Metrewave Radio Telescope to map the Coma cluster of galaxies at 250-500 MHz and 1050-1450 MHz bands. These 6.26 arcsec and 2.18 arcsec resolutions observations allow detailed radio structures to be determined of all detected radio sources that show both discrete pointlike and extended morphologies. We present images of a subset of 32 brightest (flux density >= 30 mJy) and dominant sources, and several sources show discrete pointlike radio morphologies. We find the steepening of the spectra consistent with synchrotron cooling in the majority of sources and the m…
We apply the Tapered Gridded Estimator (TGE) for estimating the cosmological 21-cm power spectrum from $150 \, {\rm MHz}$ GMRT observations which corresponds to the neutral hydrogen (HI) at redshift $z = 8.28$. Here TGE is used to measure the Multi-frequency Angular Power Spectrum (MAPS) $C_{\ell}(Δν)$ first, from which we estimate the 21-cm power spectrum $P(k_{\perp},k_{\parallel})$. The data here are much too small for a detection, and the aim is to demonstrate the capabilities of the estimator. We find that the estimated power spectrum is consistent with the expected foreground and noise b…
The cosmic evolution of bias of different source populations with underlying dark matter density field in post reionization era can shed light on large scale structures. Studying the angular and spatial distribution of different compact sources using deep radio catalogue at low-frequency is essential to understand the matter distribution of the present Universe. Here, we investigate the relationship of luminous matter with their host dark matter haloes by measuring the angular and spatial clustering of sources (two-point statistics), using deep radio observation of ELAIS N1 (EN1) field with up…
We present deep polarimetric observations of the European Large Area ISO Survey-North 1 (ELAIS-N1) field using the Low Frequency Array (LOFAR) at 114.9-177.4 MHz. The ELAIS-N1 field is part of the LOFAR Two-metre Sky Survey deep fields data release I. For six eight-hour observing epochs, we align the polarization angles and stack the 20"-resolution Stokes $Q$, $U$-parameter data cubes. This produces a 16 deg$^2$ image with 1$σ_{\rm QU}$ sensitivity of 26 $μ$Jy/beam in the central area. In this paper, we demonstrate the feasibility of the stacking technique, and we generate a catalog of polariz…
Globular Clusters GMRT Pulsar Search (GCGPS) II: Discovery of five MSPs in M69 and M70
National Centre for Radio Astrophysics (NCRA)（国家射电天文中心）；Max-Planck-Institut für Radioastronomie (MPIfR)（马克斯·普朗克射电天文研究所）；National Radio Astronomy Observatory (NRAO)（美国国家射电天文台）；Department of Physics, Silesian University in Opava（俄帕瓦西里西亚大学物理系）；Oxford e-Research Centre (OeRC) University of Oxford（牛津大学电子研究中心）；Giant Metrewave Radio Telescope (GMRT)（巨型米波射电望远镜）
We present results from 1.4 and 5 GHz observations at matched resolution with the Karl G. Jansky Very Large Array (VLA) of 11 powerful 3C FR II quasars. We examine the 11 quasars along with a sample of 13 narrow-line FR II radio galaxies and find that radio-loud unification largely holds but environmental effects cannot be ignored. The radio core prominence, largest linear size, and axial ratio parameter values indicate that quasars are at relatively smaller angles compared to the radio galaxies and thus probe orientation. Lack of correlation between statistical orientation indicators such as …
Foreground removal is a major challenge for detecting the redshifted 21-cm neutral hydrogen (HI) signal from the Epoch of Reionization (EoR). We have used 150 MHz GMRT observations to characterize the statistical properties of the foregrounds in four different fields of view. The measured multi-frequency angular power spectrum C_l(Delta nu) is found to have values in the range 10^4 mK^2 to 2 x 10^4 mK^2 across 700 <= l <= 2 x 10^4 and Delta nu <= 2.5 MHz, which is consistent with model predictions where point sources are the most dominant foreground component. The measured C_l(Delta nu) does n…
We report optical observations of TGSS J1054+5832, a candidate high-redshift ($z=4.8\pm2$) steep-spectrum radio galaxy, in $r$ and $i$ bands using the faint object spectrograph and camera mounted on 3.6-m Devasthal Optical Telescope (DOT). The source previously detected at 150 MHz from Giant Meterwave Radio Telescope and at 1420 MHz from Very Large Array has a known counterpart in near-infrared bands with $K$-band magnitude of AB 22. The source is detected in $i$-band with AB$24.3\pm0.2$ magnitude in the DOT images presented here. The source remains undetected in the $r$-band image at a 2.5$σ$…
We present a low-frequency imaging study of an extended sample of X-shaped radio sources using the Giant Metrewave radio telescope (GMRT) at two frequencies (610 and 240 MHz). The sources were drawn from a Very Large Array FIRST-selected sample and extends an initial GMRT study at the same frequencies, of 12 X-shaped radio galaxies predominantly from the 3CR catalog (Lal & Rao 2007). Both the intensity maps and spectral index maps of the 16 newly observed sources are presented. With the combined sample of 28 X-shaped radio sources, we found no systematic differences in the spectral properties …
Low radio frequencies are favourable for the identification of emission from non-thermal processes such as synchrotron emission. The massive protostellar jet associated with IRAS 18162-2048 (also known as the HH80-81 system) has been imaged at low radio frequencies: 325, 610 and 1300 MHz, using the Giant Metrewave Radio Telescope, India. This is the first instance of detection of non-thermal emission from a massive protostellar jet at such low radio frequencies. The central region displays an elongated structure characteristic of the jet. In addition, the associated Herbig-Haro objects such as…
We present Giant Metrewave Radio Telescope 610 MHz observations of 14 Atacama Cosmology Telescope (ACT) clusters, including new data for nine. The sample includes 73\% of ACT equatorial clusters with $M_{500} > 5 \times 10^{14}\;M_\odot$. We detect diffuse emission in three of these (27$^{+20}_{-14}$\%): we detect a radio mini-halo in ACT-CL J0022.2$-$0036 at $z=0.8$, making it the highest-redshift mini-halo known; we detect potential radio relic emission in ACT-CL J0014.9$-$0057 ($z=0.533$); and we confirm the presence of a radio halo in low-mass cluster ACT-CL J0256.5+0006, with flux density…
We report GMRT observation of the strong radio source 4C 35.06, an extended (z=0.047) radio-loud AGN at the center of galaxy cluster Abell 407. The radio map at 610 MHz reveal a striking, helically twisted jet system emanating from an optically faint AGN host. The radio morphology closely resembles the precessing jets of the galactic microquasar SS 433. The optical SDSS images of central region show a complex ensemble of nine galactic condensations within 1 arc minute, embedded in a faint, diffuse stellar halo. This system presents a unique case for studying the formation of a giant elliptical…
This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for the extraction of the cosmological 21-cm signal from the Low-Frequency Array - Epoch of Reionization (LOFAR-EoR) data. We use the high band antennas of LOFAR to image this region and RM-synthesis to unravel structures of polarized emission at high Galactic latitudes. The brightness temperature of the detected Galactic emission is on average 4 K in polarized intensity and covers the range from -10 to +13rad m^-2 in Faraday depth. The total polarized intensity and …
Wide-field GMRT imaging of X-shaped Radio-Galaxies: Spectral properties of 4C32.25 and 4C61.23
Astrophysics Research Centre, School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal（夸祖鲁-纳塔尔大学数学、统计与计算机科学学院天体物理研究中心）；Wits Centre for Astrophysics, School of Physics, University of the Witwatersrand（威特沃特斯兰德大学物理学院天体物理中心）
We report the discovery of one of the largest and most distant Giant Radio Galaxy (GRG) in the Lynx field which was discovered using deep Giant Metre-wave Radio Telescope (GMRT) 150 MHz observations. The core is detected at 150 MHz and also in the VLA FIRST survey. Spectroscopic observations carried out using the IUCAA Giravali Observatory(IGO) provided a redshift value of 0.57. This redshift was later confirmed with data from the Sloan Digital Sky Survey (Data Release 12). The angular size of the GRG is 5.5 arcmin and at the redshift of 0.57, its linear size is 2.2 Mpc. At this high redshift,…
The upgraded Giant Metrewave Radio Telescope (GMRT) has been used to image the head-tail radio galaxy NGC 4869 in the Coma cluster with an angular resolution of 6.26 arcsec at 250-500 MHz and 2.18 arcsec at the 1050-1450 MHz bands. The archival legacy GMRT data have also been used to image the source with angular resolutions from 4.9 to 21.8 arcsec at 610 MHz, 325 MHz, 240 MHz, and 150 MHz. We find that the ~200 kpc scale radio morphology consists of five distinct regions with the clear presence of a pinch at ~1.4 arcmin (= 38.8 kpc) and a ridge at ~3.4 arcmin (= 94.2 kpc) from the head. The s…
We aim to carry out a radio study of the SoUthern Cluster sCale Extended Source Survey (SUCCESS) sample consisting of twenty massive (M$_{500} > 5\times10^{14}$ M$_{\odot}$), nearby (redshift $<0.3$) and southern ($-50^{\circ} < δ< -30^\circ$) galaxy clusters detected by the Planck satellite and the South Pole Telescope. Here we report targeted GMRT observations (325/610 MHz) for a sub-sample of nine clusters. We also use the first data release of MeerKAT Galaxy Cluster Legacy Survey (1283 MHz) for five of these nine clusters. The properties of the mini-halo in RXC J0528.9-3927, a candidate mi…
We report quasi-simultaneous GMRT observations of seven extragalactic radio sources at 150, 325, 610 and 1400 MHz, in an attempt to accurately define their radio continuum spectra, particularly at frequencies below the observed spectral turnover. We had previously identified these sources as candidates for a sharply inverted integrated radio spectrum whose slope is close to, or even exceeds $α_c$ = +2.5, the theoretical limit due to synchrotron self-absorption (SSA) in a source of incoherent synchrotron radiation arising from relativistic particles with the canonical (i.e., power-law) energy d…
We report on a multifrequency radio study of the supernova remnant (SNR) G338.3-0.0, in positional coincidence with the TeV source HESS J1640-465. To carry out this research we observed the SNR G338.3-0.0 using the Giant Metrewave Radio Telescope (GMRT) at 235, 610, and 1280 MHz. We also reprocessed archival data from the Australia Telescope Compact Array (ATCA) at 1290 and 2300 MHz. Also we conducted a search for radio pulsations towards a central point-like source, using the GMRT antennas at 610 and 1280 MHz. The molecular material in the region of the SNR was investigated based on observati…
Ultra Steep Spectrum (USS) radio sources are one of the efficient tracers of High Redshift Radio Galaxies (HzRGs). To search for HzRGs candidates, we investigate properties of a large sample of faint USS sources derived from our deep 325 MHz GMRT observations combined with 1.4 GHz VLA data on the two subfields (i.e., VLA-VIMOS VLT Deep Survey (VVDS) and Subaru X-ray Deep Field (SXDF)) in the XMM-LSS field. The available redshift estimates show that majority of our USS sample sources are at higher redshifts with the median redshifts ~ 1.18 and ~ 1.57 in the VLA-VVDS and SXDF fields. In the VLA-…
We describe multi-frequency data designed to probe the emission mechanism that dominates in faint radio sources. Our analysis is based on observations of the Lockman Hole using the GMRT - the deepest 610-MHz imaging yet reported - together with 1.4-GHz imaging from the VLA, well matched in resolution and sensitivity to the GMRT data. The GMRT and VLA data are cross-matched to obtain the radio spectral indices for the faint radio emitters. Statistical analyses show no clear evolution for the median spectral index, alpha, as a function of flux density. alpha is found to be -0.6 to -0.7, based on…
We present low-frequency, GMRT observations at 240, 610 and 1300 MHz of IC~711, a narrow angle tail (NAT) radio galaxy. The total angular extent of the radio emission, $\sim 22$ arcmin, corresponds to a projected linear size of $\sim 900$ kpc, making it the longest among the known head-tail radio galaxies. The objectives of the GMRT observations were to investigate the radio morphology, especially of the long tail structure, at low frequencies. The radio structure, especially initial $\sim 10$ arcmin of tail being a long straight feature, does not seem to be consistent with a simple circular m…
We conducted radio interferometric observations of six pulsars at 610 MHz using the Giant Metrewave Radio Telescope (GMRT). All these objects were claimed or suspected to be the gigahertz-peaked spectra (GPS) pulsars. For a half of the sources in our sample the interferometric imaging provides the only means to estimate their flux at 610 MHz due to a strong pulse scatter-broadening. In our case, these pulsars have very high dispersion measure values and we present their spectra containing for the first time low-frequency measurements. The remaining three pulsars were observed at low frequencie…
Galaxy-cluster merger shocks efficiently accelerate the ambient electrons through diffusive shock acceleration and amplify magnetic field by compressing the Inter Cluster Medium. As a result, such objects produce a significant amount of synchrotron radio emission. Radio halo and Mpc scale peripheral radio relics thus help us to trace back the cluster formation history. To study the dynamical state of the galaxy clusters and their relation to the merging scenario, as a pilot project, we thus observed four suitable candidates from the MACS (Massive Cluster Survey) cluster sample. Observations we…
