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, SerbiaInstitute of Astronomy, Bulgarian Academy of Sciences, BulgariaAstronomical 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 name λ0 [Å] FWHM [Å] Tmax [%]

Hα 6572 32 86,7

[SII] 6719 33 83,3

Red continuum 6416 26 58

Telescope characteristics• 2 m Ritchey-Chrétien-Coudé telescope at National Astronomical Observatory Rozhen, Bulgaria• Fokus 16m• CCD camera: VersArray1300B, 1340x1300 px, scale 0”.257732/px •Field of view 5’45”x 5’35”

Filter characteristics

Observations and total exposure times• 2008 March 3• 2008 November 30• 190min 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):

ergLyrMSFR Hsun 421 1094.7

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)

12151025.26 sergcmFH

41 104.3 yrMSFR

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)

ROZHENObservations• 28th 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)

(10-15erg s-1

cm-2)

R.A.

(J2000.0).

Decl.

(J2000.0)

a1 0.085489 10 03 20.32 68 40 40.1

a2 2.730213 10 03 20.58 68 42 02.1

a3 0.248505 10 03 27.21 68 42 48.7

a4 2.12953 10 03 33.01 68 41 20.3

a5 0.095892 10 03 32.41 68 39 44.9

a6 0.606473 10 03 42.33 68 42 08.4

a7 1.191234 10 03 49.67 68 42 14.1

a8 0.331733 10 03 56.57 68 43 05.4

a9 0.530121 10 03 57.64 68 42 13.3

a10 0.039714 10 03 56.91 68 40 54.9

a11 0.730155 10 03 58.51 68 40 50.9

a12 2.18406 10 04 06.78 68 41 14.6

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 2 - 4 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 filterThree 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)

Num. α [J2000] δ [J2000] Hα flux [10-15 erg cm-2 s-1]

SII flux [10-15 erg cm-2 s-1]

[SII]/ Hα

a [arcsec]

b [arcsec]

notes

1 03:45:31.03 +68:01:57.14 2.23 2.43 1.09 1.7 2.0 Isolated object

2 03:45:33.70 +68:02:38.10 2.28 1.52 0.66 2.3 1.6 Isolated object

3 03:45:43.40 +68:02:38.40 0.68 0.53 0.78 1.3 1.3 Isolated object, low brightness

4 03:45:55.45 +68:04:53.54 25 27 1.08 4.8 7.1 Tooth nebula; X-ray source; Isolated object

5 03:46:36.01 +68:00:53.16 10.87 4.28 0.39 2.6 2.6 In HII region

6 03:46:36.08 +68:03:00.30 SNR2 (D’Odorico

et al. 1980); in HII region

7 03:46:36.60 +67:59:16.00 In HII region; low

brightness 8 03:46:50.02 +68:01:21.21 Low brightness 9 03:46:56.59 +68:02:57.97 Isolated object

10 03:47:01.15 +68:01:03.00 1.57 0.94 0.60 1.75 1.75 In HII region; low

brightness

11 03:47:03.23 +68:02:58.76 10.78 4.28 0.40 2.9 2.2 Isolated object; near HII region

12 03:47:05.48 +67:59:58.53 5.67 6.26 1.10 2.5 2.5 Isolated object; near HII region

13 03:47:19.71 +67:59:02.60 0.56 0.74 1.32 1.3 1.3 Isolated object,

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!