Optical detection of the emission nebulae in nearby galaxies DEJAN UROŠEVIĆ collaborators: Milica Vučetić, Bojan Arbutina, Konstantin Stavrev, Dragana Ilić, Aleksandra Dobardžić, Marko Pavlović, Dušan Onić, Branislav Vukotić Department of Astronomy, Faculty of Mathematics, University of Belgrade, Serbia Institute of Astronomy, Bulgarian Academy of Sciences, Bulgaria Astronomical Observatory Belgrade, Serbia

Emission nebula detection in optical range by recombination lines by forbidden lines : collisional excitation → radiative de- excitation [SII]/Hα emission-line ratios shock-heated SNRs > 0.4 photoionized nebulae < 0.4 (Blair & Long 2004, Matonick & Fesen 1997) Observations in red continuum, [SII] and Hα narrow band filters Data reduction low fluxes – long exposures – tracking problems continuum subtraction from emission-line absolute calibration with non-standard narrow-band filters IRAF and IRIS software

Goal – the detection of supernova remnants (SNRs) and HII regions in narrow band filters M81 galaxy group – interacting galaxies Higher star formation rates (SFRs) Enlarged HI concentration (radio observations) Higher supernova rates expected distance 3.7 Mpc Holmberg IX – dwarf, irregular galaxy, possibly youngest nearby dwarf galaxy (Sabbi et al. 2008) Numerous HII regions (Miller and Hodge 1994) 1 X-ray source, possible hypernova remnant or super-shell (Miller 1995, Grise et al. 2006) Observed by our group in 2008 (Arbutina et al. 2009) 20 HII region candidates

ROZHEN observatory Filter nameλ 0 [Å]FWHM [Å]T max [%] Hα ,7 [SII] ,3 Red continuum Telescope characteristics 2 m Ritchey-Chrétien-Coudé telescope at National Astronomical Observatory Rozhen, Bulgaria Fokus 16m CCD camera: VersArray1300B, 1340x1300 px, scale 0” /px Field of view 5’45”x 5’35” Filter characteristics Observations and total exposure times 2008 March November min in red continuum 140min in Hα filter 140min in [SII] filter

Star formation rate Can be found from recombination lines in HII regions around (young) massive stars – from Hα luminosity of HII regions SFR can be calculated by formula given by Kennicutt et al. (1994):

Contamination of Hα luminosity Sources of Hα luminosity which are not HII regions – other emission nebulae (planetary nebulae and SNRs!!!) [NII] lines on both sides of Hα line (654.8nm and 658.4nm) Host galaxy extinction

Results Hα flux from HII regions in Homberg IX is: Calculated star formation rate is: This SFR (Andjelić 2011) is 10 times less than given by James at al. (2004), and 6 times less than given by Karachentsev and Kaisin (2007)

NGC 3077 – dwarf galaxy rich with molecular and atomic hydrogen 6 SNR candidates, detected in radio and X range (Rosa- Gonzales 2005) numerous HII region candidates (Walter et al. 2006)

ROZHEN Observations 28 th of February 2011 Exposure time 200s 23 images through red cont. filter 23 images through [SII] filter 19 images through Hα filter

Results No SNR candidates 12 HII region candidates Andjelić et al. (2011) object Flux (Hα) ( erg s -1 cm -2 ) R.A. (J2000.0). Decl. (J2000.0) a a a a a a a a a a a a

IC342 galaxy – nearby galaxy large spiral, almost face-on galaxy, app. diameter ~20’ near Galactic plane, b ≈ 10º heavily obscured by Galactic extinction (A ~ 1.5mag) the most distance determinations are between Mpc

Previous observations 4 SNR candidates, detected in optical range (D’Odorico et al. 1980) Numerous observations in radio and X range, a few SNR candidates (Hummel & Grave 1990, Kong 2003, Mak et al. 2011) Numerous HII regions (Hodge & Kennicutt 1983) Tooth nebula – ultra-luminous X-ray source with optical, shock-heated counterpart

ROZHEN Observations 27th & 28th of November 2011 Exposure time 15 minutes 3 exposures through each filter Three fields of view

Results 13 SNR candidates 11 new SNR candidates Tooth-nebula SNR2 from D’Odorico et al. (1980) Note: SNR3 from D’Odorico et al. (1980) is HII region candidate!!! 374 HII region candidates in two fields of view (5’x5’) 666 HII region candidates in entire IC 342 (20’x20’), only positions, without fluxes ( Hodge & Kennicutt 1983)

Optical SNR candidates in IC 342 galaxy

FOV1 Hα image, continuum substracted

FOV2 Hα image, continuum substracted

Future prospects Completing galactic and extragalactic SNR and HII region samples Evolution of SNRs and HII regions Star formation rate … Optical observations are convenient method for this purpose (1 - 2 m telescopes are enough for observations of nearby galaxies) – Rozen, Vidojevica, Antalia

Regards from the Belgrade ISM gang!!!!!

THANK YOU FOR YOUR ATTENTION!