The Faint Irregular Galaxies GMRT Survey (FIGGS) is a Giant Metrewave Radio Telescope (GMRT) based H I imaging survey of a systematically selected sample of extremely faint nearby dwarf irregular galaxies. The primary goal of FIGGS is to provide a comprehensive and statistically robust characterization of the neutral interstellar medium properties of faint, gas-rich dwarf galaxies. The FIGGS galaxies represent the extremely low mass end of the dwarf irregular galaxies population, with a median M B ∼ −13.0 and median H I mass of ∼3 × 10 7 M , extending the baseline in mass and luminosity space for a comparative study of galaxy properties. The H I data are supplemented with observations at other wavelengths. In addition, distances accurate to ∼10 per cent are available for most of the sample galaxies. This paper gives an introduction to FIGGS, describes the GMRT observations and presents the first results from the H I observations. From the FIGGS data, we confirm the trend of increasing H I to optical diameter ratio with decreasing optical luminosity; the median ratio of D H I /D Ho for the FIGGS sample is 2.4. Further, on comparing our data with aperture synthesis surveys of bright spirals, we find at best marginal evidence for a decrease in average surface density with decreasing H I mass. To a good approximation, the discs of gas-rich galaxies, ranging over three orders of magnitude in H I mass, can be described as being drawn from a family with fixed H I average surface density.

We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10. • 4 degrees in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (µ V = 24.8 mag arcsec −2 ), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (R e (V ) = 12 ) and proximity (15 ) to the well-known dwarf spheroidal galaxy And II. Its red color (V − I = 1.0), shallow Sérsic index (n V = 0.68), and the absence of detectable Hα emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars.Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6-meter telescope (V h = 5450 ± 40 km s −1 ) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (∼ 78 Mpc), DGSAT I would have an R e ∼ 4.7 kpc and M V ∼ −16.3. Its properties resemble those of the ultra-diffuse galaxies recently discovered in the Coma cluster. DGSAT I is the first case of these rare ultra-diffuse galaxies found in this galaxy cluster. Unlike the ultra-diffuse galaxies associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.

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 sensitivity, GMRT HI 21cm observations. For all our galaxies we construct maps of the HI column density at a constant linear resolution of ~300 pc; this forms an excellent data set to check for the presence of a threshold column density for star formation. We find that while current star formation (as traced by Halpha emission) is confined to regions with relatively large (N_HI > (0.4 -1.7) X 10^{21} atoms cm^{-2}) HI column density, the morphology of the Halpha emission is in general not correlated with that of the high HI column density gas. Thus, while high column density gas may be necessary for star formation, in this sample at least, it is not sufficient to ensure that star formation does in fact occur. We examine the line profiles of the HI emission, but do not find a simple relation between regions with complex line profiles and those with on-going star formation. Finally, we examine the very fine scale (~20-100 pc) distribution of the HI gas, and find that at these scales the emission exhibits a variety of shell like, clumpy and filamentary features. The Halpha emission is sometimes associated with high density HI clumps, sometimes the Halpha emission lies inside a high density shell, and sometimes there is no correspondence between the Halpha emission and the HI clumps. In summary, the interplay between star formation and gas density in these galaxy does not seem to show the simple large scale patterns observed in brighter galaxies (abridged).Comment: 15 pages, 6 tables, 13 figures. Accepted for publication in MNRA

We present images for 36 galaxies of the M81 group obtained in the Hα line. Estimates of the Hα flux and star formation rate, SFR, are avialable now for all the known members of the group with absolute magnitudes down to M B = −10 m .The character of distribution of the galaxies over three paremeters: M B , SFR, and total hydrogen mass permits us to draw the following conclusions as to evolution status of the group population. a) Spiral and irregular type galaxies would have time to generate their luminosity (baryon mass) during the cosmological time T 0 = 13.7 Gyr, but dwarf spheroidal objects are capable of reproducing only ∼5% of their observed luminosity. b) S and Im,BCD galaxies possess the supply of gas sufficient to maintain their observed SFRs during only next (1/4 -1/3)T 0 years, while dIr and dSph populations have the mean gas depletion time about 3 T 0 . c) There is indirect evidence that the star formation in Im, BCD and dIr galaxies proceeds in a mode of vigorous burst activity rather than in the form of a sluggish process. We note the dwarf tidal system near NGC 3077, the Garland, to have the highest SFR per unit luminosity among 150 galaxies of the Local volume with known SFRs.Being averaged over the local "cell of homogeneity" of 4 Mpc in diameter around M 81, the rate of star formation of the group,ρ SF R = 0.165M ⊙ /year·Mpc 3 , proves to be 5-8 times higher than, that of the average global rate at Z =0. Karachentsev I.D.,

After recent systematic optical, IR, and HI surveys, the total number of known galaxies within 10 Mpc has increased from 179 to 550. About half this Local Volume (LV) sample is now been imaged with HST, yielding the galaxy distances with an accuracy of about 8%. For the majority of the LV galaxies we currently have H-alpha fluxes that allow us to reconstruct the star formation history of our neighbourhood. For the late-type LV galaxies their HI masses and angular momentum follow the linear relation in the range of 4 orders, which is expected for rotating gaseous disks being near the gravitational instability threshold. The data obtained on the LV galaxies imply important cosmological parameters, in particular, the mean local matter density and HI mass density, as well as SFR density. Surprisingly, the local Hubble flow around the LV groups is very quiet, with 1D rms deviations of 25 km/s,which is a signature of the Universe vacuum-dominated on small scales. The cold infall pattern around nearby groups provides us with a new method to determine the total mass of the groups independent from virial mass estimates.Comment: 10 pages, 6 figures, proceedings Symposium "Galaxies in the Local Volume", Sydney, 8 - 13 July 2007, B. Koribalski and H. Jerjen, ed