We present the results of spectroscopic and morphological studies of the galaxy UGC7388 with the 8.1-m Gemini North telescope. Judging by its observed characteristics, UGC7388 is a giant late-type spiral galaxy seen almost edge-on. The main body of the galaxy is surrounded by two faint (μ(B) ~ 24 and μ(B) ~ 25.5) extended (~20-30 kpc) loop-like structures. A large-scale rotation of the brighter loop about the main galaxy has been detected. We discuss the assumption that the tidal disruption of a relatively massive companion is observed in the case of UGC7388. A detailed study and modeling of the observed structure of this unique galaxy can give important information about the influence of the absorption of massive companions on the galactic disks and about the structure of the dark halo around UGC7388.
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 (V$_{rot} \sim$ 31 km/s). This V$_{rot}$ is in line with that of dwarf galaxies with similar HI mass. We estimate an M$_{dyn}$ of $\sim$ 1.14 $\times$ 10$^{9}$ M$_\odot$ within the galaxy's R$_{HI}$ $\sim$ 5.2 kpc. Additionally, our estimates of M$_{200}$ for the galaxy from NFW models are in the range of 5.0 to 8.8 $\times$ 10$^{10}$ M$_\odot$. Comparing UGC 216…
The dominant physical processes responsible for the formation and longevity of giant gaseous and stellar discs in galaxies remain controversial. Although they are rare (less than 10 confirmed as of now), giant low-surface brightness (gLSB) discy galaxies provide interesting insights given their extreme nature. We describe observations of UGC 1378 including deep spectroscopy with the Russian 6m telescope and multi-band imaging with Binospec at the MMT. Galaxy UGC 1378 has both high surface brightness and an extended low surface brightness discs. Our stellar velocity dispersion data for the high…
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 source exhibits a compact core coincident with the optical quasar and two lobes separated by ~7 kpc, all at an impact parameter ~25 kpc. The HI 21-cm absorption detected towards the southern lobe is found to extend over ~2 kpc^2. The absorbing gas shows sub-kpc-scale structures with the line-of-sight velocities dominated by turbulent motions. Much larger opt…
We present a method to recover and study the projected gravitational tidal forces from a galaxy survey containing little or no redshift information. The method and the physical interpretation of the recovered tidal maps as a tracer of the cosmic web are described in detail. We first apply the method to a simulated galaxy survey and study the accuracy with which the cosmic web can be recovered in the presence of different observational effects, showing that the projected tidal field can be estimated with reasonable precision over large regions of the sky. We then apply our method to the 2MASS s…
The existence of long-lived galaxies lacking dark matter represents a challenge to our understanding of how galaxies form. Here, we present evidence that explains the lack of dark matter in one of such galaxies: NGC1052-DF4. Deep optical imaging of the system has detected tidal tails in this object caused by its interaction with its neighbouring galaxy NGC1035. As stars are more centrally concentrated than the dark matter, the tidal stripping will remove a significant percentage of the dark matter before affecting the stars of the galaxy. Only ~7% of the stellar mass of the galaxy is in the ti…
