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A set of diffuse interstellar clouds in the inner Galaxy within a few hundred pc of the Galactic plane has been observed at an angular resolution of ~1 arcmin combining data from the NRAO Green Bank Telescope and the Very Large Array. At…

Astrophysics of Galaxies · Physics 2015-06-15 Yurii Pidopryhora , Felix J. Lockman , John M. Dickey , Michael P. Rupen

We present the early science results from a blind search of the extragalactic HI 21-cm absorption lines at z $\leqslant$ 0.09 with the drift-scan observation of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We carried…

We have carried out deep, high velocity resolution, interferometric Galactic HI 21 cm absorption spectroscopy towards 32 compact extra-galactic radio sources with the Giant Metrewave Radio Telescope (GMRT) and the Westerbork Synthesis Radio…

Astrophysics of Galaxies · Physics 2014-07-30 Nirupam Roy , Nissim Kanekar , Robert Braun , Jayaram N. Chengalur

We have searched for HI 21cm absorption toward the two brightest radio AGN at high redshift, J0924--2201 at $z = 5.20$, and J0913+5919 at $z=5.11$, using the Giant Meter Wave Radio Telescope (GMRT). These data set a 3$\sigma$ upper limit to…

Astrophysics · Physics 2008-11-26 C. L. Carilli , Ran Wang , M. van Hoven , K. Dwarakanath , J. Chengalur , S. Wyithe

We have used the Westerbork Synthesis Radio Telescope to detect HI 21cm absorption at $z \sim 0.7645$ in the gravitational lens system towards PMN J0134-0931. The 21cm profile has two broad components, with peak optical depths of $0.047 \pm…

Astrophysics · Physics 2009-11-10 N. Kanekar , F. H. Briggs

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…

Astrophysics · Physics 2009-11-10 A. Omar , K. S. Dwarakanath

We report results from a deep search for redshifted HI 21cm absorption in 55 strong MgII$\lambda$2796 absorbers (having $W (MgII) > 0.5 \AA$) at intermediate redshifts, $0.58 < z_{\rm abs} < 1.70$, with the Green Bank Telescope (GBT) and…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 N. Kanekar , J. X. Prochaska , S. L. Ellison , J. N. Chengalur

We have searched for HI 21-cm absorption in 11 strong MgII systems ($W_{\rm r}$(MgII $\lambda 2796$) $\ge 1$ \AA) at $0.3<z<0.5$ using the Giant Metrewave Radio Telescope. We have detected HI 21-cm absorption in two of these. From the…

Astrophysics of Galaxies · Physics 2017-04-12 Rajeshwari Dutta , Raghunathan Srianand , Neeraj Gupta , Ravi Joshi

We present an extragalactic HI 21-cm absorption lines catalog from a blind search at z $\leqslant$ 0.35, using drift-scan data collected in 1325.6 hours by the ongoing Commensal Radio Astronomy FasT Survey (CRAFTS) and FAST All Sky HI…

We report the discovery of eleven high-velocity HI clouds at Galactic latitudes of 25-30 degrees, likely embedded in the Milky Way's nuclear wind. The clouds are detected with deep Green Bank Telescope 21 cm observations of a $3.2^\circ…

Astrophysics of Galaxies · Physics 2025-07-08 Rongmon Bordoloi , Andrew J. Fox , Felix J. Lockman

Recent targeted studies of associated HI absorption in radio galaxies are starting to map out the location, and potential cosmological evolution, of the cold gas in the host galaxies of Active Galactic Nuclei (AGN). The observed 21 cm…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 J. R. Allison , E. M. Sadler , S. J. Curran , S. N. Reeves

We present results from a search for 21 cm associated HI absorption in a sample of 29 radio sources selected from the Australia Telescope 20 GHz survey. Observations were conducted using the Australia Telescope Compact Array Broadband…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 J. R. Allison , S. J. Curran , B. H. C. Emonts , K. Gareb , E. K. Mahony , S. Reeves , E. M. Sadler , A. Tanna , M. T. Whiting , M. A. Zwaan

As a complement to the HyGAL Stratospheric Observatory for Infrared Astronomy Legacy Program, we report the results of a ground-based absorption line survey of simple molecules in diffuse and translucent Galactic clouds. Using the Institut…

We present a pilot study of extragalactic HI 21-cm absorption lines using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We observed 5 continuum sources with HI absorption features firstly identified in the 40% data…

Astrophysics of Galaxies · Physics 2021-03-31 Bo Zhang , Ming Zhu , Zhong-Zu Wu , Qing-Zheng Yu , Peng Jiang , You-Ling Yue , Meng-Lin Huang , Qiao-Li Hao

We present an analysis of the HI absorption in a sample of 101 flux-selected radio AGN (S_1.4 GHz > 50 mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). HI absorption is detected in 32 galaxies, showing a broad variety of…

Astrophysics of Galaxies · Physics 2015-06-23 K. Gereb , F. M. Maccagni , R. Morganti , T. A. Oosterloo

We present the results from our 21-cm absorption survey of a sample of 5 quasar-galaxy pairs (QGPs), with the redshift of the galaxies in the range 0.03<zg<0.18, selected from the SDSS. The HI 21-cm absorption was searched towards the 9…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-19 N. Gupta , R. Srianand , D. V. Bowen , D. G. York , Y. Wadadekar

The VLA Galactic Plane Survey (VGPS) of the first Galactic quadrant was searched for HI emission with velocities well above the maximum velocity allowed by Galactic rotation. A sample of 17 small fast-moving clouds was identified. The…

This study presents results on detecting neutral atomic hydrogen (HI) 21cm absorption in the spectrum of PKS1413+135 at redshift $z=0.24670041$. The observation was conducted by FAST, with a spectral resolution of 10 Hz, using 10 minutes of…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-08 Jiangang Kang , Chang-Zhi Lu , TongJie Zhang , Ming Zhu

WSRT observations have provided a first inventory of the incidence of HI 21 cm line absorption associated with AGN at redshifts up to z=1.0. There is a large range in line depths, from tau=0.44 to tau less than 0.001, and a substantial…

Astrophysics · Physics 2007-05-23 R. C. Vermeulen

We present an HI absorption survey of the central 250 pc of the Galaxy. Very Large Array (VLA) observations were made at 21 cm in the DnC and CnB configurations and have a resolution of ~15"(0.6 pc at the Galactic Center (GC) distance) and…

Astrophysics of Galaxies · Physics 2015-05-20 Cornelia C. Lang , W. Miller Goss , Claudia Cyganowski , Kelsey I. Clubb