First optical detection of the supernova remnant G 15.1-1.6

Free access article

Issue		A&A Volume 481, Number 3, April III 2008


Page(s)		705 - 712
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20079156
Published online		07 February 2008

A&A 481, 705-712 (2008)
DOI: 10.1051/0004-6361:20079156

First optical detection of the supernova remnant G 15.1-1.6

P. Boumis¹, J. Alikakos^{1, 2}, P. E. Christopoulou², F. Mavromatakis³, E. M. Xilouris¹, and C. D. Goudis^{1, 2}

¹ Institute of Astronomy & Astrophysics, National Observatory of Athens, I. Metaxa & V. Paulou, P. Penteli, 15236 Athens, Greece
    e-mail: [ptb;johnal;xilouris;cgoudis]@astro.noa.gr
² Astronomical Laboratory, Department of Physics, University of Patras, 26500 Rio-Patras, Greece
    e-mail: pechris@upatras.physics.gr
³ Technological Education Institute of Crete, General Department of Applied Science, PO Box 1939, 710 04 Heraklion, Crete, Greece
    e-mail: fotis@physics.uoc.gr

(Received 27 November 2007 / Accepted 17 January 2008)

Abstract
Deep optical CCD images of the supernova remnant G 15.1-1.6 were obtained where filamentary and diffuse emission was discovered. The images, taken in the emission lines of H $\alpha+[$ $\ion{N}{ii}$ ], [S II], and [ $\ion{O}{iii}$ ], reveal filamentary and diffuse structures all around the remnant. The radio emission at 4850 MHz in the same area is found to be strongly correlated with the brightest optical filaments. The IRAS 60 $\mu$ m emission may also be correlated with the optical emission but to a lesser extent. The flux-calibrated images suggest that the optical emission originates from shock-heated gas ([S II]/H $\alpha$ > 0.4), while there is a possible $\ion{H}{ii}$ region ([S II]/H $\alpha$ ~ 0.3) contaminating the supernova remnant's emission to the east. Furthermore, deep long-slit spectra were taken at two bright filaments and also show that the emission originates from shock-heated gas. An [ $\ion{O}{iii}$ ] filamentary structure is also detected farther to the west, but it lies outside the remnant's boundaries and may not be associated to it. The [ $\ion{O}{iii}$ ] flux suggests shock velocities into the interstellar ``clouds" ~100 km s^-1, while the [ $\ion{S}{ii}$ $]\lambda\lambda\ 6716/6731$ ratio indicates electron densities up to ~250 cm^-3. Finally, the H $\alpha$ emission is measured to be between 2 to $7 \times$ 10^-16 erg s^-1 cm^-2 arcsec^-2, while the lower limit to the distance is estimated at 2.2 kpc.

Key words: ISM: general -- ISM: supernova remnants -- ISM: individual objects: G15.1-1.6

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