Devasthal Fast Optical Telescope Observations of Wolf–Rayet Dwarf Galaxy Mrk 996

Abstract

The Devasthal Fast Optical Telescope (DFOT) is a 1.3 meter aperture optical telescope, recently installed at Devasthal, Nainital. We present here the first results using an Hα filter with this telescope on a Wolf–Rayet dwarf galaxy Mrk 996. The instrumental response and the Hα sensitivity obtained with the telescope are (3.3 ± 0.3) × 10⁻¹⁵ erg s⁻¹ cm⁻² /counts s⁻¹ and 7.5 × 10⁻¹⁷ erg s⁻¹ cm⁻² arcsec⁻² respectively. The Hα flux and the equivalent width for Mrk 996 are estimated as (132± 37) × 10⁻¹⁴ erg s⁻¹ cm⁻² and ∼96 Å respectively. The star formation rate is estimated as 0.4 ± 0.1M yr⁻¹ . Mrk 996 deviates from the radio- FIR correlation known for normal star forming galaxies with a deficiency in its radio continuum. The ionized gas as traced by Hα emission is found in a disk shape which is misaligned with respect to the old stellar disk. This misalignment is indicative of a recent tidal interaction in the galaxy. We believe that galaxy–galaxy tidal interaction is the main cause of the WR phase in Mrk 996.