Optical observations of M81 galaxy group in narrow band [SII] and Hα filters: Holmberg IX

Abstract

We present observations of the nearby tidal dwarf galaxy Holmberg IX in M81 galaxy group in narrow band [SII] and Hα filters, carried out in March and November 2008 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for resident supernova remnants (identified as sources with enhanced [SII] emission relative to their Hα emission) in this galaxy yielded no sources of this kind, besides M&H 10-11 or HoIX X-1. Nevertheless, we found a number of objects with significant Hα emission that probably represent uncatalogued HII regions.

Star formation rate in Holmberg IX dwarf galaxy

“…In this paper we use Hα fluxes for Holmberg IX given in Arbutina et al (2009). Observations were taken with the 2 m Ritchey-Chrétien-Coudé (RCC) telescope at the National Astronomical Observatory (NAO) Rozhen, Bulgaria.…”

“…Observations were taken with the 2 m Ritchey-Chrétien-Coudé (RCC) telescope at the National Astronomical Observatory (NAO) Rozhen, Bulgaria. The galaxy was observed through Hα, [SII] and red continuum narrow band filters (see Table 2 in Arbutina et al 2009 for details). The total exposure time through each filter was 140, 140 and 190 minutes, respectively.…”

“…The total exposure time through each filter was 140, 140 and 190 minutes, respectively. Arbutina et al (2009) reported 22 objects detected in the Hα filter (see Fig. 1).…”

“…Other 21 objects represent HII region candidates. Their absolute flux calibration was performed by using the fluxes of sources identified both by Arbutina et al (2009) and by Miller and Hodge (1994).…”

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In this paper we use previously determined Hα fluxes for dwarf galaxy Holmberg IX (Arbutina et al 2009) to calculate star formation rate (SFR) in this galaxy. We discuss possible contaminations of Hα flux and, for the first time, we take into account optical emission from supernova remnants (SNRs) as a possible source of contamination of Hα flux.

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