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Publications (5)5.52 Total impact

  • Source
    I. Leonidaki, P. Boumis, A. Zezas
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    ABSTRACT: We present results from a study of optically emitting Supernova Remnants (SNRs) in six nearby galaxies (NGC 2403, NGC 3077, NGC 4214, NGC 4395, NGC 4449 and NGC 5204) based on deep narrow band H{\alpha} and [SII] images as well as spectroscopic observations. The SNR classification was based on the detected sources that fulfill the well-established emission line flux criterion of [SII]/H{\alpha} > 0.4. This study revealed ~400 photometric SNRs down to a limiting H{\alpha} flux of 10^(-15) erg sec^(-1) cm^(-2). Spectroscopic observations confirmed the shock-excited nature of 56 out of the 96 sources with ([SII]/H{\alpha})$_{phot}$> 0.3 (our limit for an SNR classification) for which we obtained spectra. 11 more sources were spectroscopically identified as SNRs although their photometric [SII]/H{\alpha} ratio was below 0.3. We discuss the properties of the optically-detected SNRs in our sample for different types of galaxies and hence different environments, in order to address their connection with the surrounding interstellar medium. We find that there is a difference in [NII]/H{\alpha} line ratios of the SNR populations between different types of galaxies which indicates that this happens due to metallicity. We cross-correlate parameters of the optically detected SNRs ([SII]/H{\alpha} ratio, luminosity) with parameters of coincident X- ray emitting SNRs, resulted from our previous studies in the same sample of galaxies, in order to understand their evolution and investigate possible selection effects. We do not find a correlation between their H{\alpha} and X-ray luminosities, which we attribute to the presence of material in a wide range of temperatures. We also find evidence for a linear relation between the number of luminous optical SNRs (10^(37) erg sec^(-1)) and SFR in our sample of galaxies.
    Monthly Notices of the Royal Astronomical Society 11/2012; 429(1). · 5.52 Impact Factor
  • I. Leonidaki, P. Boumis, A. Zezas
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    ABSTRACT: We present the detection of new optically emitting Supernova Remnants (SNRs) in six nearby galaxies, using deep narrow band Halpha and [S II] images as well as spectroscopic observations. The SNR classification was based on the detected sources that fulfill the well-established emission line flux criterion of [S II]/Halpha > 0.4. This study revealed ~400 photometric SNRs down to a limiting flux of 10-16 erg/sec /cm2, ~350 of which are new identifications. 130 photometric SNRs were spectroscopically observed and 63 outlined their shock-excited nature, verifying that the used photometric method is a robust diagnostic tool for the preliminary identification of SNRs. We compare the derived SNR properties (such as electron density, luminosity, number of SNRs) in different types of galaxies and hence different environments, in order to investigate their interaction with the surrounding interstellar medium. We also cross-correlate parameters of the optically detected SNRs ([S II]/Halpha ratio, luminosity) with parameters (temperature, luminosity) of coincident X- ray emitting SNRs, resulted from our previous studies in the same sample of galaxies, in order to understand their evolution and investigate possible selection effects.
    01/2012;
  • I. Leonidaki, A. Zezas, P. Boumis
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    ABSTRACT: We present the results from a study of the SNR populations in six nearby galaxies (NGC 2403, NGC 3077, NGC 4214, NGC 4395, NGC 4449 and NGC 5204) based on Chandra archival data. We have detected a sample of 244 discrete X-ray sources with fluxes down to 10-17 erg s-1 cm-2. A total number of 37 X-ray detected SNRs are identified, 30 of which are new, based on their X-ray colors and spectroscopy. We discuss the SNR properties (luminosity, temperature, density) of the X-ray detected SNRs in order to obtain information on their interaction with their environment. We also compare the luminosity distributions of X-ray SNRs in different types of galaxies with the number of our X-ray detected SNRs and we indicate differences between the SNR populations in spiral and irregular galaxies. On the basis of a multi-wavelength study of SNRs, we obtained deep images in the [S II] and Hα emission lines and we initially classified a large number of optical candidate SNRs based on their [S II] / Hα ratio. Follow-up spectro-photometric observations for a number of the candidate SNRs have also been obtained and their spectral signatures suggest that the detected emission originates from shock-heated gas.
    07/2010;
  • [show abstract] [hide abstract]
    ABSTRACT: We propose to obtain optical spectra of photometrically selected SNRs in 5 nearby galaxies (NGC 3077, NGC 4214, NGC 4395, NGC 4449 and NGC 5204), based on narrow-line imaging. In that way, we will confirm these identifications and obtain an accurate sample of extragalactic SNRs. These observations will provide a 2 order-of-magnitude improvement in sensitivity over similar previous surveys and therefore a more complete and representative picture of the SNR populations in different galactic environments. They will supplement existing deep Chandra observations by confirming the X-ray classification of the identified sample of thermal X-ray SNRs and will allow us to link their X-ray properties (temperature, luminosity) to their optical properties (H(alpha) luminosity, density) and local environment.
    NOAO Proposal. 02/2010;
  • 07/2008;