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Search: authors:"Ayesha Begum"

8 papers found.
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A study of interstellar medium of dwarf galaxies using H i power spectrum analysis

We estimate the power spectrum of H i intensity fluctuations for a sample of eight galaxies (seven dwarf and one spiral). The power spectrum can be fitted to a power-law for six of these galaxies, indicating turbulence is operational. The estimated best-fitting value for the slope ranges from ∼−1.5 (AND IV, NGC 628, UGC 4459 and GR 8) to ∼−2.6 (DDO 210 and NGC 3741). We interpret...

Star formation in extremely faint dwarf galaxies

We study the relationship between the gas column density (Σgas) and the star formation rate (SFR) surface density (ΣSFR) for a sample of 23 extremely faint dwarf irregular galaxies drawn from the Faint Irregular Galaxy GMRT (Giant Metrewave Radio Telescope) Survey (FIGGS). Our sample galaxies have a median H i mass of 2.8 × 107 M⊙ and a median blue magnitude MB∼−13.2. ΣSFR is...

A search for H i in some peculiar faint dwarf galaxies

We present a deep Giant Metrewave Radio Telescope (GMRT) search for H i 21-cm emission from three dwarf galaxies, viz. POX 186, SC 24 and KKR 25. Based, in part, on previous single-dish H i observations, these galaxies have been classified as a blue compact dwarf (BCD), a dwarf irregular and a transition galaxy, respectively. However, in conflict with previous single-dish...

FIGGS: Faint Irregular Galaxies GMRT Survey – overview, observations and first results

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...

Baryonic Tully–Fisher relation for extremely low mass Galaxies

We study Tully–Fisher (TF) relations for a sample that combines extremely faint (MB < −14) galaxies along with bright (i.e. ∼L*) galaxies. Accurate (∼10 per cent) distances, I-band photometry and B−V colours are known for the majority of the galaxies in our sample. The faint galaxies are drawn from the Faint Irregular Galaxy GMRT survey (FIGGS), and we have H i rotation...

Life in the last lane: star formation and chemical evolution in an extremely gas rich dwarf

We present an analysis of H i, Hα and oxygen abundance data for NGC 3741. This galaxy has a very extended gas disc (∼8.8 times the Holmberg radius), and a dark-to-luminous (i.e. stellar) mass ratio of ∼149, which makes it one of the ‘darkest’ dwarf irregular galaxies known. However, its ratio of baryon (i.e. gas + stellar) mass to dark mass is typical of that in galaxies. Our new...

Gas distribution, kinematics and star formation in faint dwarf galaxies

We compare the gas distribution, kinematics and the current star formation in a sample of 10 very faint (−13.37 < MB < −9.55) dwarf galaxies. For five of these galaxies we present fresh, high-sensitivity, Giant Metrewave Radio Telescope H i 21-cm observations. We find that the large-scale H i distribution in the galaxies is typically irregular and clumpy, with the peak gas...

The Local Group dwarf Leo T: H i on the brink of star formation

We present Giant Meterwave Radio Telescope (GMRT) and Westerbork Synthesis Radio Telescope (WSRT) observations of the recently discovered Local Group dwarf galaxy, Leo T. The peak H i column density is measured to be 7 × 1020cm−2, and the total H i mass is 2.8 × 105M⊙, based on a distance of 420 kpc. Leo T has both cold (∼500 K) and warm (∼6000 K) H i at its core, with a global...