Revealing the nature of central emission nebulae in the dwarf galaxy NGC 185

In this paper we present new optical observations of the galaxy NGC 185 intended to reveal the status of supernova remnants (SNRs) in this dwarf companion of the Andromeda galaxy. Previously, it was reported that this galaxy hosts one SNR. Our deep photometric study with the 2m telescope at Rozhen National Astronomical Observatory using narrow-band H$\alpha$ and [SII] filters revealed complex structure of the interstellar medium in the center of the galaxy. To confirm the classification and to study the kinematics of the detected nebulae, we carried out spectroscopic observations using the SCORPIO multi-mode spectrograph at the 6m telescope at the Special Astrophysical Observatory of the Russian Academy of Science, both in low- and high-resolution modes. We also searched the archival X-ray and radio data for counterparts of the candidate SNRs identified by our optical observations. Our observations imply the presence of one more SNR, one possible HII region previously cataloged as part of an SNR, and the presence of an additional source of shock ionization in one low-brightness PN. We detected enhanced [SII]/H_alpha and [NII]/H_alpha line ratios, as well as relatively high (up to 90 km s$^{-1}$) expansion velocities of the two observed nebulae, motivating their classification as SNRs (with diameters of 45 pc and 50 pc), confirmed by both photometric and spectral observations. The estimated electron density of emission nebulae is 30 - 200 cm$^{-3}$. Archival XMM-Newton observations indicate the presence of an extended, low-brightness, soft source in projection of one of the optical SNRs, whereas the archival VLA radio image shows weak, unresolved emission in the center of NGC 185.Comment: 15 pages, 14 figures, accepted for publication in A&

Observatons of NGC 3077 Galaxy in Narrow Band [SII] and H_alpha Filters

We present observations of the HI tidal arm near dwarf galaxy NGC 3077 (member of the M81 galaxy group) in narrow band [SII] and H_alpha filters. Observations were carried out in March 2011 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for possible supernova remnant candidates (identified as sources with enhanced [SII] emission relative to their H_alpha emission) in this region yielded no sources of this kind. Nevertheless, we found a number of objects with significant H_alpha emission that probably represent uncatalogued, low brightness HII regions.Comment: 4 pages, 1 figure, 3 tables, Proceedings of the 8th Serbian Conference on Spectral Line Shapes in Astrophysics, 2011 June 5-10, Divcibare, Serbi

Optical Observations of M81 Galaxy Group in Narrow Band [SII] and H_alpha Filters: Holmberg IX

We present observations of the nearby tidal dwarf galaxy Holmberg IX in M81 galaxy group in narrow band [SII] and H$\alpha$ 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 H$\alpha$ 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 H$\alpha$ emission that probably represent uncatalogued HII regions.Comment: 8 pages, 5 figure

The orthogonal fitting procedure for determination of the empirical {\Sigma} - D relations for supernova remnants: application to starburst galaxy M82

The radio surface brightness-to-diameter ({\Sigma} - D) relation for supernova remnants (SNRs) in the starburst galaxy M82 is analyzed in a statistically more robust manner than in the previous studies that mainly discussed sample quality and related selection effects. The statistics of data fits in log {\Sigma} - log D plane are analyzed by using vertical (standard) and orthogonal regressions. As the parameter values of D - {\Sigma} and {\Sigma} - D fits are invariant within the estimated uncertainties for orthogonal regressions, slopes of the empirical {\Sigma} - D relations should be determined by using the orthogonal regression fitting procedure. Thus obtained {\Sigma} - D relations for samples which are not under severe influence of the selection effects could be used for estimating SNR distances. Using the orthogonal regression fitting procedure {\Sigma} - D slope {\beta} \approx 3.9 is obtained for the sample of 31 SNRs in M82. The results of implemented Monte Carlo simulations show that the sensitivity selection effect does not significantly influence the slope of M82 relation. This relation could be used for estimation of distances to SNRs that evolve in denser interstellar environment, with number denisty up to 1000 particles per cm3 .Comment: 14 pages, 3 figures, no changes, previous version had a typo in publication related comment, accepted for publication in Ap

Aging of the geiger-muller counter due to particle conductance in an insulating gas

In this paper, the aging effect of commercially available Geiger-Muller counters under working conditions is being considered from both theoretical and experimental point of view. In the experimental part lifetime curves for the commercial Geiger-Muller counter chamber are first recorded. After detection of the aging phenomena, the commercial chamber response to an impulse voltage is tested along with recording of the same response of the Geiger-Muller chamber model with conductive particles included. The law of similarity for the gaseous discharge is fulfilled both by the commercial Geiger-Muller chamber and by the chamber model with conductive particles. The results obtained from the U-test indicate that the aging of the Geiger-Muller chamber is mainly caused by the occurrence of a great number of conductive particles hovering inside the chamber. Some suggestions of how to reduce the aging effect due to conductive particles inside the Geiger-Muller chamber are given in the conclusion

Aging of the geiger-muller counter due to particle conductance in an insulating gas

In this paper, the aging effect of commercially available Geiger-Muller counters under working conditions is being considered from both theoretical and experimental point of view. In the experimental part lifetime curves for the commercial Geiger-Muller counter chamber are first recorded. After detection of the aging phenomena, the commercial chamber response to an impulse voltage is tested along with recording of the same response of the Geiger-Muller chamber model with conductive particles included. The law of similarity for the gaseous discharge is fulfilled both by the commercial Geiger-Muller chamber and by the chamber model with conductive particles. The results obtained from the U-test indicate that the aging of the Geiger-Muller chamber is mainly caused by the occurrence of a great number of conductive particles hovering inside the chamber. Some suggestions of how to reduce the aging effect due to conductive particles inside the Geiger-Muller chamber are given in the conclusion

Optical observations of NGC 1156 galaxy in narrowband [SII] and Hα filters

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