* Astronomy

Blobrana · L

PGC 27077

Blobrana · L

NGC 2905

Blobrana · L

RE: NGC 2903

Blobrana · L

Title: Hot Diffuse Emission in the Nuclear Starburst Region of NGC 2903
Authors: Mihoko Yukita, Douglas A. Swartz, Allyn F. Tennant, Roberto Soria, Jimmy A. Irwin

We present a deep Chandra observation of the late-type barred spiral galaxy NGC 2903. The Chandra data reveal soft (kT_e ~ 0.2-0.5keV) diffuse emission in the nuclear starburst region and extending ~5kpc to the north and west of the nucleus. Much of this soft hot gas is likely to be from local active star-forming regions; however, besides the nuclear region, the morphology of hot gas does not strongly correlate with sites of active star formation. The central ~650 pc radius starburst zone exhibits much higher surface brightness diffuse emission than the surrounding regions and a harder spectral component in addition to its soft component. We interpret the hard component as being of thermal origin with kT_e~3.6keV and to be directly associated with a wind fluid produced by supernovae and massive star winds. The inferred terminal velocity for this hard component, ~1100 km/s, exceeds the local galaxy escape velocity suggesting a potential outflow. The softer extended emission does not display an obvious outflow geometry. However, the column density through which the X-rays are transmitted is lower to the west of the nucleus compared to the east and the surface brightness is higher there suggesting some soft hot gas originates from above the disk; viewed directly from the western zone but through the intervening galaxy disk from the eastern zone. There are several point-like sources in the nuclear region with X-ray spectra typical of compact binaries. None of these are coincident with the mass center of the galaxy and we place an upper limit luminosity from any point-like nuclear source to be < 2x10^38 ergs/s in the 0.5-8.0keV band which indicates that NGC 2903 lacks an active galactic nucleus. Heating from the nuclear starburst and a galactic wind may be responsible for preventing cold gas from accreting onto the galactic center.

Read more (2805kb, PDF)

Blobrana · L

Expand (53kb, 1024 x 768)

Date: 02:07 UTC, 23rd February 2012

180 second exposure with Rich Field telescope.

NGC 2903 is a barred spiral galaxy about 30 million light-years away in the constellation Leo.
With an apparent magnitude (V) of 9.7 it is visible with small telescopes.

Blobrana · L

Expand (15kb, 1024 x 768)

Date: 01:30 UTC, 23rd February 2011

Blobrana · L

Title: XMM-Newton observations of the hot spot galaxy NGC 2903
Authors: D. Perez-Ramirez, M.D. Caballero-Garcia, J. Ebrero, S. Leon

We report on the first deeper X-ray broad-band observation of the hot spot galaxy NGC 2903 obtained with XMM-Newton. X-ray imaging and spectra of the spiral barred galaxy NGC 2903 were obtained from recently available XMM-Newton archival data in order to study its X-ray population and the conditions of the hot gas in its central region. We investigate the spectral properties for the discrete point-source population and give first estimations of their X-ray spectral parameters. By analysing the RGS spectra, we derive temperature and abundances for the hot gas located in its central region. A total of 6 X-ray point sources (4 of them ULX candidates) were detected in the energy range of 0.3-10.0 keV located within the galaxy D25 optical disk. 3 out of these sources are detected for the first time, and one of them, XMM-NGC2903 X2 with luminosity larger than 10^39 erg/s. After fitting three different models, we were able to estimate their luminosities which are compatible with binaries with a compact object in the form of BHs rather than of NS. We extracted the combined first-order RGS1 and RGS2 spectra of its central region, which show several emission lines. The spectrum is dominated by a strong O,{viii} Ly \alpha emission line along with Ne,{x} Ly \alpha, and several Fe,{xvii} features. We fitted the spectrum to a model for a plasma in collisional ionisation equilibrium (CIE) and the continuum was modelled with a power law, resulting in a plasma temperature of T = 0.31 ±0.01 keV and an emission measure EM \equiv n_Hn_eV =6.4_{-0.4}^{+0.5} x 10^{61}~cm^{-3}. We also estimated abundances which are consistent with solar values.

Read more (224kb, PDF)

Blobrana · L

Title: An optical search for supernova remnants in the nearby spiral galaxy NGC 2903
Authors: E. Sonbas (CU; Sao of R.A.S.), A. Akyuz (CU), S. Balman (METU)

We present the results of an optical search for supernova remnants (SNRs) in the nearby spiral galaxy NGC 2903. Interference filter images and spectral data were taken in March 2005 with the f/7.7 1.5 m Russian Turkish Telescope (RTT150) at TUBITAK National Observatory (TUG). Spectral data were obtained with the 6 m BTA (Bolshoi Azimuthal Telescope, Russia). We used the SNR identification criterion that consists of constructing the continuum-subtracted H \alpha and continuum-subtracted [SII] \lambda \lambda 6716,6731 images and their ratios. Five SNR candidates were identified in NGC 2903 with [SII]/H \alpha ratios ranging from 0.41 - 0.74 and H \alpha intensities ranging from 9.4 x10^{-15} to 1.7 x 10^{-14} ergs cm^{-2} s^{-1}. This work represents the first identification of SNRs by an optical survey in NGC 2903. We present the spectrum of one of the bright candidates and derive an [SII]/H \alpha emission line ratio of 0.42 for this source. In addition, the weak [OIII] \lambda 5007/H \beta emission line ratio in the spectrum of this SNR indicates an old oxygen-deficient remnant with a low propagation velocity.

Read more (896kb, PDF)

Blobrana · L

Title: LCDM Satellites and HI Companions - The Arecibo ALFA Survey of NGC 2903
Authors: J. A. Irwin, G. L. Hoffman, K. Spekkens, M. P. Haynes, R. Giovanelli, S. M. Linder, B. Catinella, E. Momjian, B. S. Koribalski, J. Davies, E. Brinks, W. J. G. de Blok, M. E. Putman, W. van Driel

We have conducted a deep, complete HI survey, using Arecibo/ALFA, of a field centered on the nearby, isolated galaxy, NGC 2903, which is similar to the Milky Way in its properties. The field size was 150 kpc x 260 kpc and the final velocity range spanned from 100 to 1133 km/s. The ALFA beams have been mapped as a function of azimuth and cleaned from each azimuth-specific cube prior to forming final cubes. The final HI data are sensitive down to an HI mass of 2 x 10^5 Mo and column density of 2 x 10^{17} cm^{-2} at the 3sigma x 2deltaV level, where sigma is the rms noise level and deltaV is the velocity resolution. NGC 2903 is found to have an HI envelope that is larger than previously known, extending to at least 3 times the optical diameter of the galaxy. Our search for companions yields one new discovery with an HI mass of 2.6 x 10^6 Mo. The companion is 64 kpc from NGC 2903 in projection, is likely associated with a small optical galaxy of similar total stellar mass, and is dark matter dominated, with a total mass >10^8 Mo. In the region surveyed, there are now two known companions: our new discovery and a previously known system that is likely a dwarf spheroidal, lacking HI content. If HI constitutes 1% of the total mass in all possible companions, then we should have detected 230 companions, according to LCDM predictions. Consequently, if this number of dark matter clumps are indeed present, then they contain less than 1% HI content, possibly existing as very faint dwarf spheroidals or as starless, gasless dark matter clumps.

Read more (451kb, PDF)