A metallicity-spin temperature relation in damped Lyman-$\alpha$ systems (2009)
Kanekar, Nissim, Smette, Alain, Briggs, Frank H., Chengalur, Jayaram N.
We report evidence for an anti-correlation between spin temperature $T_s$ and metallicity [Z/H], detected at $3.6 \sigma$ significance in a sample of 26 damped Lyman-$\alpha$ absorbers (DLAs) at...
The HI gas content of galaxies around Abell 370, a galaxy cluster at z = 0.37 (2009)
Lah, Philip, Pracy, Michael B., Chengalur, Jayaram N., Briggs, Frank H., Colless, Matthew, De Propris, Roberto, ...
We used observations from the Giant Metrewave Radio Telescope to measure the atomic hydrogen gas content of 324 galaxies around the galaxy cluster Abell 370 at a redshift of z = 0.37 (a look-back...
Probing Turbulence in the Interstellar Medium of Galaxies (2009)
Dutta, Prasun, Begum, Ayesha, Bharadwaj, Somnath, Chengalur, Jayaram N.
The power spectrum of HI intensity fluctuation of the interstellar medium carries information of the turbulence dynamics therein. We present a method to estimate the power spectrum of HI intensity...
A Study of ISM of Dwarf Galaxies Using HI Power Spectrum Analysis (2009)
Dutta, Prasun, Begum, Ayesha, Bharadwaj, Somnath, Chengalur, Jayaram N.
We estimate the power spectrum of HI intensity fluctuations for a sample of 8 galaxies (7 dwarf and one spiral). The power spectrum can be fitted to a power law P_HI(U) = A U^\alpha for 6 of these...
The Scale Height of NGC 1058 Measured from its HI Power Spectrum (2009)
Dutta, Prasun, Begum, Ayesha, Bharadwaj, Somnath, Chengalur, Jayaram N.
We have measured the HI power spectrum of the nearly face-on spiral galaxy NGC 1058 from radio-interferometric observations using a visibility based estimator. The power spectrum is well fitted by...
HI in very metal-poor galaxies: the SBS 0335-052 system (2009)
Ekta, B., Pustilnik, Simon A., Chengalur, Jayaram N.
We present Giant Metrewave Radio Telescope (GMRT), HI 21cm observations of SBS 0335-052E and SBS 0335-052W, a close pair of dwarf galaxies, which are further unusual in being the most metal-poor...
Star formation in extremely faint dwarf galaxies (2009)
Roychowdhury, Sambit, Chengalur, Jayaram N., Begum, Ayesha, Karachentsev, Igor D.
We study the relationship between the gas column density (derived from GMRT 21 cm data) and the star formation rate surface density (derived from publicly available GALEX data) for a sample of 23...
Magnetohydrodynamic turbulence in supernova remnants (2008)
Roy, Nirupam, Bharadwaj, Somnath, Dutta, Prasun, Chengalur, Jayaram N.
We present estimates of the angular power spectra of the synchrotron radiation intensity fluctuations at 6 and 20 cm for the shell type supernova remnant Cas A and the filled-centre Crab supernova...
HI and star formation in the most metal-deficient galaxies (2008)
Chengalur, Jayaram N., Pustilnik, S. A.
We present Giant Metrewave Radio Telescope (GMRT) observations for three (viz., DDO 68, SDSS J2104-0035 and UGC 772) of the six most metal-deficient actively star-forming galaxies known. Although...
Turbulence measurements from HI absorption spectra (2008)
Roy, Nirupam, Peedikakkandy, Leshma, Chengalur, Jayaram N.
We use the millennium Arecibo 21 cm absorption-line survey measurements to examine the issue of the non-thermal contribution to the observed Galactic HI line widths. If we assume a simple, constant...
FIGGS: Faint Irregular Galaxies GMRT Survey - Overview, observations and first results (2008)
Begum, Ayesha, Chengalur, Jayaram N., Karachentsev, I. D., Sharina, M. E., Kaisin, S. S.
The Faint Irregular Galaxies GMRT Survey (FIGGS) is a Giant Metrewave Radio Telescope (GMRT) based HI imaging survey of a systematically selected sample of extremely faint nearby dwarf irregular...
Baryonic Tully-Fisher Relation for Extremely Low Mass Galaxies (2008)
Begum, Ayesha, Chengalur, Jayaram N., Karachentsev, I. D., Sharina, M. E.
We study Tully-Fisher relations for a sample that combines extremely faint (M_B > -14.0) galaxies along with bright (i.e. L_*) galaxies. Accurate (~ 10%) distances, I band photometry, and B-V colors...
Foregrounds for redshifted 21 cm studies of reionization: GMRT 153 MHz observations (2008)
Ali, SK. Saiyad, Bharadwaj, Somnath, Chengalur, Jayaram N.
Foreground subtraction is the biggest challenge for future redshifted 21 cm observations to probe reionization. We use a short GMRT observation at 153 MHz to characterize the statistical properties...
Gas rich galaxies from the FIGGS survey (2007)
Chengalur, Jayaram N., Begum, Ayesha, Karachentsev, I. D., Sharina, Margarita, Kaisin, S. S.
The FIGGS (Faint Irregular Galaxy GMRT Survey) is aimed at creating a multi-wavelength observational data base for a volume limited sample of the faintest gas rich galaxies. In this paper we discuss...
FIGGS: Faint Irregular Galaxies GMRT Survey (2007)
Begum, Ayesha, Chengalur, Jayaram N., Karachentsev, I. D., Sharina, Margarita, Kaisin, S. S.
The Faint Irregular Galaxies GMRT Survey (FIGGS) is a large program aimed at providing a comprehensive and statistically robust characterisation of the neutral ISM properties of faint (M_B > -14.5),...
Life in the last lane: Star formation and chemical evolution in an extremely gas-rich dwarf (2007)
Begum, Ayesha, Chengalur, Jayaram N., Kennicutt, Robert C., Karachentsev, Igor D., Lee, Janice C.
We present an analysis of HI, H-alpha, and oxygen abundance data for NGC 3741. This galaxy has a very extended gas disk (~8.8 times the Holmberg radius), and a dark to luminous (i.e. stellar) mass...
HI power spectrum of the spiral galaxy NGC628 (2007)
Dutta, Prasun, Begum, Ayesha, Bharadwaj, Somnath, Chengalur, Jayaram N.
We have measured the HI power spectrum of the nearly face-on spiral galaxy NGC628 (M74) using a visibility based estimator. The power spectrum is well fitted by a power law $P(U)=AU^{\alpha}$, with...
Outflowing atomic and molecular gas at $z \sim 0.67$ towards 1504+377 (2007)
Kanekar, Nissim, Chengalur, Jayaram N.
We report the detection of OH 1667 MHz and wide HI 21cm absorption at $z \sim 0.67$ towards the red quasar 1504+377, with the Green Bank Telescope and the Giant Metrewave Radio Telescope. The HI 21cm...
A search for H I 21 cm absorption toward the highest redshift (z~5.2) radio-loud objects (2007)
Carilli, C.L., Wang, Ran, Van Hoven, M.B., Dwarakanath, K.S., Chengalur, Jayaram N., Wyithe, Stuart
Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
The HI content of star-forming galaxies at z = 0.24 (2007)
Lah, Philip, Chengalur, Jayaram N., Briggs, Frank H., Colless, Matthew, De Propris, Roberto, Pracy, Michael B., ...
We use observations from the Giant Metrewave Radio Telescope (GMRT) to measure the atomic hydrogen gas content of star-forming galaxies at z = 0.24 (i.e. a look-backtime of ~3 Gyr). The sample of...
HI studies of eXtremely Metal Deficient galaxies - II: GMRT observations of SBS 1129+576 (2006)
Chengalur, Jayaram N., Pustilnik, Simon A.
We present GMRT HI observations of an eXtremely Metal Deficient (XMD) galaxy SBS 1129+576 (12 + log(O/H) = 7.41). Our HI observations show that the galaxy is strongly interacting with a companion...
HI in XMD Galaxies III. GMRT observations of BCG HS0822+3542 (2006)
Chengalur, Jayaram N., Pustilnik, S. A., Kniazev, A. Y.
We present Giant Metrewave Radio Telescope (GMRT) HI 21-cm line data for the smallest known eXtremely Metal Deficient (XMD) blue compact galaxy (BCG) HS0822+3542. From HST imaging it has been...
Power spectrum of HI intensity fluctuations in DDO 210 (2006)
Begum, Ayesha, Chengalur, Jayaram N., Bharadwaj, Somnath
We measure the power spectrum of HI intensity fluctuations in the extremely faint (M_B ~ -10.9) dwarf galaxy DDO 210 using a visibility based estimator that is well suited in very low signal to noise...
A multiwavelength investigation of the temperature of the cold neutral medium (2005)
Roy, Nirupam, Chengalur, Jayaram N., Srianand, Raghunathan
We present measurements of the H I spin temperatures (T_s) of the Cold Neutral Medium (CNM) towards radio sources that are closely aligned with stars for which published H_2 ortho-para temperatures...
Gas distribution, kinematics and star formation in faint dwarf galaxies (2005)
Begum, Ayesha, Chengalur, Jayaram. N., Karachentsev, I. D., Kaisin, S. S., Sharina, M. E.
We compare the gas distribution, kinematics and the current star formation in a sample of 10 very faint (-13.37 < M_B < -9.55) dwarf galaxies. For 5 of these galaxies we present fresh, high...
A search for HI in some peculiar faint dwarf galaxies (2005)
Begum, Ayesha, Chengalur, Jayaram N.
We present a deep Giant Metrewave Radio Telescope (GMRT) search for HI 21 cm emission from three dwarf galaxies, viz. POX 186, SC 24 and KKR 25. Based, in part, on previous single dish HI...
Resolving the mystery of the dwarf galaxy HIZSS003 (2005)
Begum, Ayesha, Chengalur, Jayaram N., Karachentsev, I. D., Sharina, M. E.
The nearby galaxy HIZSS003 was recently discovered during a blind HI survey of the zone of avoidance (Henning et al. 2000). Follow up VLA as well as optical and near-IR imaging and spectroscopy...
The strange case of a sub-DLA with very little HI (2004)
Kanekar, Nissim, Chengalur, Jayaram N.
We report a deep search for HI 21cm emission from the $z= 0.00632$ sub-DLA toward PG1216+069 with the Giant Metrewave Radio Telescope. No emission was detected and our $5\sigma$ upper limit on the...
The GMRT study of extremely faint dwarf irregular galaxies (2004)
Begum, Ayesha, Chengalur, Jayaram N.
We present results of deep, high velocity resolution ($\sim$1.6 kms$^{-1}$) Giant Meterwave Radio Telescope (GMRT) HI 21 cm-line observations of a sample of extremely faint (M$_B>-$12.5) dwarf...
Kinematics of two dwarf galaxies in the NGC 6946 group (2004)
Begum, Ayesha, Chengalur, Jayaram N.
We present high velocity resolution (~ 1.6 km/s) Giant Meterwave Radio Telescope (GMRT) HI 21 cm synthesis images of the dwarf galaxies KK98 250 and KK98 251, as well as optical broad band images of...
Conjugate 18cm OH Satellite Lines at a Cosmological Distance (2004)
Kanekar, Nissim, Chengalur, Jayaram N., Ghosh, Tapasi
We have detected the two 18cm OH satellite lines from the $z \sim 0.247$ source PKS1413+135, the 1720 MHz line in emission and the 1612 MHz line in absorption. The 1720 MHz luminosity is $L_{\rm OH}...
The temperature of the WNM in the Milky Way (2003)
Kanekar, Nissim, Subrahmanyan, Ravi, Chengalur, Jayaram N., Safouris, Vicky
We report high spectral resolution Australia Telescope Compact Array HI 21 cm observations resulting in the detection of the warm neutral medium (WNM) of the Galaxy in absorption against two...
Constraining the variation of fundamental constants using 18cm OH lines (2003)
Chengalur, Jayaram N., Kanekar, Nissim
We describe a new technique to estimate variations in the fundamental constants using 18cm OH absorption lines. This has the advantage that all lines arise in the same species, allowing a clean...
The use of OH "main" lines to constrain the variation of fundamental constants (2003)
Kanekar, Nissim, Chengalur, Jayaram N
We describe a new technique to measure variations in the fundamental parameters $\alpha$ and $y \equiv m_e/m_p$, using the sum of the frequencies of cm-wave OH ``main'' lines. The technique is $\sim$...
Kinematics of the dwarf irregular galaxy GR8 (2003)
Begum, Ayesha, Chengalur, Jayaram N.
We present deep, high velocity resolution (~1.6 km/s) Giant Meterwave Radio Telescope HI 21cm synthesis images for the faint (M_B ~ -12.1) dwarf irregular galaxy GR8. We find that the velocity field...
Kinematics of Extremely Faint Dwarf Galaxies (2003)
Begum, Ayesha, Chengalur, Jayaram N.
We present the results of deep, high velocity resolution (~1.6 km/s) Giant Meterwave Radio Telescope (GMRT) HI 21cm observations of extremely faint (M_B > -12.5) dwarf irregular galaxies. We find...
Kinematics of the faintest gas rich galaxy in the Local Group: DDO210 (2003)
Begum, Ayesha, Chengalur, Jayaram N.
We present deep, high velocity resolution (~1.6 km/s) Giant Meterwave Radio Telescope (GMRT) HI 21cm synthesis images of the faint (M_B ~ -10.6) local group dwarf galaxy DDO210. We find that the HI...
Widespread acetaldehyde near the Galactic Centre (2003)
Chengalur, Jayaram N., Kanekar, Nissim
We present Giant Meterwave Radio Telescope images of the 1065 MHz emission from the 1_11 -> 1_10 rotational transition of acetaldehyde (CH3CHO) in the molecular cloud complex Sgr B2. Our observations...
The little galaxy that could: Kinematics of Camelopardalis B (2003)
Begum, Ayesha, Chengalur, Jayaram N., Hopp, Ulrich
We present deep, high velocity resolution (1.6 km/s) GMRT HI as well as optical data for the faint (M_B ~ -10.9) galaxy Camelopardalis B. We find that the HI in the galaxy has a regular velocity...
A deep search for 21cm absorption in high redshift damped Lyman-$\alpha$ systems (2002)
Kanekar, Nissim, Chengalur, Jayaram N
We present deep GMRT 21cm absorption spectra of 10 damped Lyman-$\alpha$ systems (DLAs), of which 8 are at redshifts $z \ga 1.3$. HI absorption was detected in only one DLA, the $z = 0.5318$ absorber...
HI 21cm imaging of a nearby Damped Lyman-alpha system (2002)
Chengalur, Jayaram N., Kanekar, Nissim
We present Giant Metrewave Radio Telescope (GMRT) HI 21cm emission images of the z=0.009 damped Lyman-alpha (DLA) absorber towards the QSO HS 1543+5921. The DLA has been earlier identified as a low...
A new 21-cm absorber identified with an $L \sim L^\star$ galaxy (2001)
Kanekar, Nissim, Athreya, Ramana M., Chengalur, Jayaram N.
We present Giant Metrewave Radio Telescope (GMRT) observations of redshifted 21-cm absorption from the $z=0.437$ metal line absorption system towards PKS 1243-072. HI absorption is clearly detected;...
Molecular gas at intermediate redshifts (2001)
Kanekar, Nissim, Chengalur, Jayaram N
We present Giant Metrewave Radio Telescope (GMRT) observations of OH absorption in B3~1504+377 ($z \sim 0.673$) and PKS 1413+135 ($z \sim 0.247$). OH has now been detected in absorption towards four...
Chengalur, Jayaram N., Braun, R., Wieringa, M.
We discuss Australia Telescope Compact Array (ATCA) HI 21cm data for the galaxy cluster A3128. Our observations are intentionally relatively shallow, and a blind search through our data cube yields...
Detection of a multi-phase ISM at $z=0.2212$ (2001)
Kanekar, Nissim, Ghosh, Tapasi, Chengalur, Jayaram N
We present sensitive Giant Metrewave Radio Telescope (GMRT) and high-resolution Arecibo HI 21-cm observations of the damped Lyman-$\alpha$ absorber (DLA) at $z=0.2212$ towards OI 363. The spectra are...
GMRT Observations of Interstellar Clouds in the 21cm line of Atomic Hydrogen (2001)
Mohan, Rekhesh, Dwarakanath, K. S., Srinivasan, G., Chengalur, Jayaram N.
Nearby interstellar clouds with high (|v| >/= 10 km/s) random velocities although easily detected in NaI and CaII lines have hitherto not been detected (in emission or absorption) in the HI 21cm...
Variable 21cm absorption at z=0.3127 (2001)
Kanekar, Nissim, Chengalur, Jayaram N
We report multi-epoch GMRT HI observations of the z = 0.3127 damped absorber towards the quasar PKS 1127-145, which reveal variability in both the absorption profile and the flux of the background...
HI 21cm absorption in low z damped lyman-alpha systems (2001)
Kanekar, Nissim, Chengalur, Jayaram N.
We report Giant Metrewave Radio Telescope (GMRT) 21cm observations of two confirmed and one candidate low redshift damped Lyman-alpha systems (DLAS). HI absorption was detected in the two confirmed...
ATCA search for 21 cm emission from a candidate damped Ly-$\alpha$ absorber at z = 0.101 (2000)
Kanekar, Nissim, Chengalur, Jayaram N, Subrahmanyan, Ravi, Petitjean, Patrick
We report a deep search for 21 cm emission/absorption from the $z \sim 0.101$ candidate damped Lyman-$\alpha$ system towards PKS 0439-433, using the Australia Telescope Compact Array (ATCA). The...
Implications of 21cm observations for damped Ly-$\alpha$ systems (2000)
Chengalur, Jayaram N, Kanekar, Nissim
We present Giant Metrewave Radio Telescope HI 21cm absorption observations, of candidate and confirmed damped Lyman-$\alpha$ systems (DLAS). The derived spin temperatures (T_s) are in all cases $\sim...
Mohan, Rekhesh, Dwarakanath, K. S., Srinivasan, G., Chengalur, Jayaram N.
We have made HI 21cm-line absorption measurements using the GMRT towards 15 directions in the Galaxy which are known to have high random velocity clouds as seen in the optical absorption lines of...
HI and OH absorption at z=0.89 (1999)
Chengalur, Jayaram N., De Bruyn, A. G., Narasimha, D.
We report on WSRT observations of HI and OH absorption at z=0.885 towards the radio lens PKS 1830-21, mm wave transitions of several molecular species have already been observed at this redshift. At...
GMRT Observations of Low z Damped Lyman-alpha Absorbers (1998)
Chengalur, Jayaram N, Kanekar, Nissim
We present Giant Metrewave Radio Telescope (GMRT) observations of redshifted HI 21cm absorption in two low redshift (z=0.2212, z=0.0912) damped Lyman-alpha systems seen towards the gigahertz peaked...
ORT observations of the damped Lyman alpha system towards PKS 0201+113 (1997)
Kanekar, Nissim, Chengalur, Jayaram N
We report a deep radio search with the Ooty Radio Telescope (ORT) for the redshifted 21 cm absorption line from the damped Lyman alpha system seen at redshift 3.388 against the quasar PKS 0201+113....
Chengalur, Jayaram N., Braun, Robert, Burton, W. Butler
We report on a deep search with the Westerbork Synthesis Radio Telescope towards the galactic anticenter for the 327 MHz hyperfine transition of DI. This is a favorable direction for a search...
A radio Search for high redshift HI absorption (1995)
Chengalur, Jayaram N., De Bruyn, A. G., Braun, R., Carilli, C. L.
Ground based optical observations have yielded considerable information on the statistics of damped-lyman alpha systems. In particular these systems are known to be the dominant repository of the...