Related papers: High-Latitude HI in the Low Surface Brightness Gal…
We have used the Very Large Array to image the isolated ``superthin'' galaxy UGC7321 in the HI line with a spatial resolution of 16'' and a spectral resolution of 24 kHz (5.2 km/s). We have reached a sensitivity of ~0.38 mJy/bm per channel,…
This is the fourth paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. We observed for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force…
We explore the vertical light distribution as a function of galactocentric radius in the edge-on (i=88) Sd `superthin' galaxy UGC7321. UGC7321 is a low-luminosity spiral (M_B,i=-17.0) with a diffuse, low surface brightness stellar disk and…
This is the third paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. For this purpose we need to analyse the observed XV diagrams in edge-on galaxies to accurately measure the radial…
We theoretically study the vertical structure of the edge-on low surface brightness (LSB) galaxy UGC 7321. This is one of the few well-observed LSBs. We modeled it as a gravitationally coupled disk system of stars and atomic hydrogen gas in…
A study is presented of HI line observations of the nearby spiral galaxy NGC 3521 observed with the VLA as part of The HI Nearby Galaxy Survey. Clearly evident in the HI data cube is the presence of an anomalous HI component that is both…
Our GMRT HI observations of the ultra diffuse galaxy (UDG) UGC 2162, projected $\sim$ 300 kpc from the centre of the M77 group, reveal it to a have an extended HI disk (R$_{HI}$/R$_{25}$ $\sim$ 3.3) with a moderate rotational velocity…
The neutral hydrogen line profiles along the major axis of the nearby spiral galaxy NGC 2403 show a wing towards the sytemic velocity. This asymmetry can be explained with the presence of an abnormally thick HI disk (FWHM ~ 5 kpc) or with a…
We present B- and R-band imaging and photometry, H-alpha narrow-band imaging, NIR H-band imaging, and HI 21-cm spectroscopy of the nearby Sd spiral galaxy UGC7321. UGC7321 exhibits a remarkably thin stellar disk with no bulge component. The…
The thickness of the neutral hydrogen layer, coupled with the rotation curve, traces the outer dark matter potential. We estimate the amplitude of the flaring in spiral galaxies from a 3D model of the HI gas. Warps in particular are…
We present full modeling of tangent point emission of HI as seen in the 21 cm transition in the inner Galaxy ($R \simeq 3-8 \kpc$). The model used takes into account emission from a large path length along the line of sight, corresponding…
Recent, high sensitivity, HI observations of nearby spiral galaxies show that their thin `cold' disks are surrounded by thick layers (halos) of neutral gas with anomalous kinematics. We present results for three galaxies viewed at different…
Very sensitive HI 21cm observations have been made in 860 directions at dec >= -43deg in search of weak, Galactic, high-velocity HI emission lines at moderate and high Galactic latitudes. One-third of the observations were made toward…
We report the first $5\sigma$ detection of HI 21 cm emission from a star-forming galaxy at redshift $z\sim1.3$ (nearly 9 billion years ago) using upgraded Giant Metrewave Radio Telescope (uGMRT). This is the highest redshift HI detection in…
Gas velocity dispersions provide important diagnostics of the forces counteracting gravity to prevent collapse of the gas. We use the 21 cm line of neutral atomic hydrogen (HI) to study HI velocity dispersion and HI phases as a function of…
Observations indicate that some extended outer disks have a sharp cut off in the surface density of neutral hydrogen when this approaches the value of $\sim 2\times 10^{19}$ cm$^{-2}$. In this paper we model these HI edges as places where…
We combine new VLA D array HI data of NGC 2613 with previous high resolution data to show new disk-halo features in this galaxy. The global HI distribution is modeled in detail using a technique which can disentangle the effects of…
We study the properties of HI gas in the outer regions (~2r_25) of a spiral galaxy, UGC 00439 (z = 0.01769), using HI 21-cm absorption towards different components of an extended background radio source, J0041$-$0043 (z = 1.679). The radio…
Neutral hydrogen observations of the nearby, edge-on spiral galaxy NGC 891 reveal the presence of an HI halo extending up to at least 5 kpc from the plane. This halo gas appears to rotate 25 to 100 km/s more slowly than the gas in the…
Aims: We derive the 3-D HI volume density distribution for the Galactic disk out to R = 60 kpc. Methods: Our analysis is based on parameters for the warp and rotation curve derived previously. The data are taken from the…