Far-infrared properties of cluster galaxies

Far-infrared properties are derived for a sample of over 200 galaxies in seven clusters: A262, Cancer, A1367, A1656 (Coma), A2147, A2151 (Hercules), and Pegasus. The IR-selected sample consists almost entirely of IR normal galaxies, with Log of L(FIR) = 9.79 solar luminosities, Log of L(FIR)/L(B) = 0,79, and Log of S(100 microns)/S(60 microns) = 0.42. None of the sample galaxies has Log of L(FIR) greater than 11.0 solar luminosities, and only one has a FIR-to-blue luminosity ratio greater than 10. No significant differences are found in the FIR properties of HI-deficient and HI-normal cluster galaxies

van der Kruit to Spitzer: A New Look at the FIR-Radio Correlation

We present an initial look at the far infrared-radio correlation within the star-forming disks of four nearby, nearly face-on galaxies (NGC~2403, NGC~3031, NGC~5194, and NGC~6946). Using {\it Spitzer} MIPS imaging and WSRT radio continuum data, we are able to probe variations in the logarithmic 70~$\mu$m/22~cm ($q_{70}$) flux density ratios across each disk at sub-kpc scales. We find general trends of decreasing $q_{70}$ with declining surface brightness and with increasing radius. We also find that the dispersion in $q_{70}$ within galaxies is comparable to what is measured {\it globally} among galaxies at around 0.2 dex. We have also performed preliminary phenomenological modeling of cosmic ray electron (CR$e^{-}$) diffusion using an image-smearing technique, and find that smoothing the infrared maps improves their correlation with the radio maps. The best fit smoothing kernels for the two less active star-forming galaxies (NGC~2403 and NGC~3031) have much larger scale-lengths than that of the more active star-forming galaxies (NGC~5194 and NGC~6946). This difference may be due to the relative deficit of recent CR$e^{-}$ injection into the interstellar medium (ISM) for the galaxies having largely quiescent disks.Comment: 6 pages, 3 figures, To appear in the proceedings of the "Island Universes: Structure and Evolution of Disk Galaxies" conference held in Terschelling, Netherlands, July 2005, ed. R. de Jong (Springer: Dordrecht

Several New Active Galactic Nuclei Among X-ray Sources Detected by INTEGRAL and SWIFT Observatories

We present the results of the optical identifications of a set of X-ray sources from the all-sky surveys of INTEGRAL and SWIFT observatories. Optical data were obtained with Russian-Turkish 1.5-m Telescope (RTT150). Nine X-ray sources were identified as active galactic nuclei (AGNs). Two of them are hosted by nearby, nearly exactly edge-on, spiral galaxies MCG -01-05-047 and NGC 973. One source, IGR J16562-3301, is most probably BL Lac object (blazar). Other AGNs are observed as stellar-like nuclei of spiral galaxies, with broad emission lines in their spectra. For the majority of our hard X-ray selected AGNs, their hard X-ray luminosities are well-correlated with the luminosities in [OIII],5007 optical emission line. However, the luminosities of some AGNs deviate from this correlation. The fraction of these objects can be as high as 20%. In particular, the flux in [OIII] line turns to be lower in two nearby edge-on spiral galaxies, which can be explained by the extinction in their galactic disks.Comment: 9 pages, 3 figures, accepted for publication in Astronomy Letters, the original text in Russian can be found at http://hea.iki.rssi.ru/~rodion/poptid.pd

Confirmation of SBS 1150+599A As An Extremely Metal-Poor Planetary Nebula

SBS 1150+599A is a blue stellar object at high galactic latitude discovered in the Second Byurakan Survey. New high-resolution images of SBS 1150+599A are presented, demonstrating that it is very likely to be an old planetary nebula in the galactic halo, as suggested by Tovmassian et al (2001). An H-alpha image taken with the WIYN 3.5-m telescope and its "tip/tilt" module reveals the diameter of the nebula to be 9.2", comparable to that estimated from spectra by Tovmassian et al. Lower limits to the central star temperature were derived using the Zanstra hydrogen and helium methods to determine that the star's effective temperature must be > 68,000K and that the nebula is optically thin. New spectra from the MMT and FLWO telescopes are presented, revealing the presence of strong [Ne V] lambda 3425, indicating that the central star temperature must be > 100,000K. With the revised diameter, new central star temperature, and an improved central star luminosity, we can constrain photoionization models for the nebula significantly better than before. Because the emission-line data set is sparse, the models are still not conclusive. Nevertheless, we confirm that this nebula is an extremely metal-poor planetary nebula, having a value for O/H that is less than 1/100 solar, and possibly as low as 1/500 solar.Comment: 19 pages, 6 figures. Accepted for publication in the Astronomical Journa

The Herschel Virgo Cluster Survey: I. Luminosity functions

We describe the Herschel Virgo Cluster Survey (HeViCS) and the first data obtained as part of the Science Demonstration Phase (SDP). The data cover a central 4x4 sq deg region of the cluster. We use SPIRE and PACS photometry data to produce 100, 160, 250, 350 and 500 micron luminosity functions (LFs) for optically bright galaxies that are selected at 500 micron and detected in all bands. We compare these LFs with those previously derived using IRAS, BLAST and Herschel-ATLAS data. The Virgo Cluster LFs do not have the large numbers of faint galaxies or examples of very luminous galaxies seen previously in surveys covering less dense environments.Comment: Letter accepted for publication in A&A (Herschel special issue

High-resolution radio continuum survey of M33 II. Thermal and nonthermal emission

We determine the variation in the nonthermal radio spectral index in the nearby spiral galaxy M33 at a linear resolution of 360 pc. We separate the thermal and nonthermal components of the radio continuum emission without the assumption of a constant nonthermal spectral index. Using the Spitzer FIR data at 70 and 160 $\mu$m and a standard dust model, we deredden the H$\alpha$ emission. The extinction corrected H$\alpha$ emission serves as a template for the thermal free-free radio emission. Subtracting from the observed 3.6 cm and 20 cm emission (Effelsberg and the VLA) this free-free emission, we obtain the nonthermal maps. A constant electron temperature used to obtain the thermal radio intensity seems appropriate for M~33 which, unlike the Milky Way, has a shallow metallicity gradient. For the first time, we derive the distribution of the nonthermal spectral index across a galaxy, M33. We detect strong nonthermal emission from the spiral arms and star-forming regions. Wavelet analysis shows that at 3.6 cm the nonthermal emission is dominated by contributions from star-forming regions, while it is smoothly distributed at 20 cm. For the whole galaxy, we obtain thermal fractions of 51% and 18% at 3.6 cm and 20 cm, respectively. The thermal emission is slightly stronger in the southern than in the northern half of the galaxy. We find a clear radial gradient of mean extinction in the galactic plane. The nonthermal spectral index map indicates that the relativistic electrons suffer energy-loss when diffusing from their origin in star-forming regions towards interarm regions and the outer parts of the galaxy. We also conclude that the radio emission is mostly nonthermal at R $>$ 5 kpc in M33.Comment: 15 pages, 14 figures, accepted for publication in the Astronomy and Astrophysics journa

Morphology of the 12-micron Seyfert Galaxies: II. Optical and Near-Infrared Image Atlas

We present 263 optical and near-infrared (NIR) images for 42 Seyfert 1s and 48 Seyfert 2s, selected from the Extended 12-micron Galaxy Sample. Elliptically-averaged profiles are derived from the images, and isophotal radii and magnitudes are calculated from these. We also report virtual aperture photometry, that judging from comparison with previous work, is accurate to roughly 0.05mag in the optical, and 0.07mag in the NIR. Our B-band isophotal magnitude and radii, obtained from ellipse fitting, are in good agreement with those of RC3. When compared with the B band, V, I, J, and K isophotal diameters show that the colors in the outer regions of Seyferts are consistent with the colors of normal spirals. Differences in the integrated isophotal colors and comparison with a simple model show that the active nucleus+bulge is stronger and redder in the NIR than in the optical. Finally, roughly estimated Seyfert disk surface brightnesses are significantly brighter in B and K than those in normal spirals of similar morphological type.Comment: 17 pgs including figures; Table 2 is a separate file. Complete Figure 1 is available by contacting the authors. Accepted for publication in ApJ

Radio-loud Narrow-Line Type 1 Quasars

We present the first systematic study of (non-radio-selected) radio-loud narrow-line Seyfert 1 (NLS1) galaxies. Cross-correlation of the `Catalogue of Quasars and Active Nuclei' with several radio and optical catalogues led to the identification of 11 radio-loud NLS1 candidates including 4 previously known ones. Most of the radio-loud NLS1s are compact, steep spectrum sources accreting close to, or above, the Eddington limit. The radio-loud NLS1s of our sample are remarkable in that they occupy a previously rarely populated regime in NLS1 multi-wavelength parameter space. While their [OIII]/H_beta and FeII/H_beta intensity ratios almost cover the whole range observed in NLS1 galaxies, their radio properties extend the range of radio-loud objects to those with small widths of the broad Balmer lines. Among the radio-detected NLS1 galaxies, the radio index R distributes quite smoothly up to the critical value of R ~ 10 and covers about 4 orders of magnitude in total. Statistics show that ~7% of the NLS1 galaxies are formally radio-loud while only 2.5% exceed a radio index R > 100. Several mechanisms are considered as explanations for the radio loudness of the NLS1 galaxies and for the lower frequency of radio-louds among NLS1s than quasars. While properties of most sources (with 2-3 exceptions) generally do not favor relativistic beaming, the combination of accretion mode and spin may explain the observations. (abbreviated)Comment: Astronomical Journal (first submitted in Dec. 2005); 45 pages incl. 1 colour figur

Galaxy Flow in the Canes Venatici I Cloud

We present an analysis of Hubble Space Telescope/WFPC2 images of eighteen galaxies in the Canes Venatici I cloud. We derive their distances from the luminosity of the tip of the red giant branch stars with a typical accuracy of ~12 %. The resulting distances are 3.9 Mpc (UGC 6541), 4.9 Mpc (NGC 3738), 3.0 Mpc (NGC 3741), 4.5 Mpc (KK 109), >6.3 Mpc (NGC 4150), 4.2 Mpc (UGC 7298), 4.5 Mpc (NGC 4244), 4.6 Mpc (NGC 4395), 4.9 Mpc (UGC 7559), 4.2 Mpc (NGC 4449), 4.4 Mpc (UGC 7605), 4.6 Mpc (IC 3687), 4.7 Mpc (KK 166), 4.7 Mpc (NGC 4736), 4.2 Mpc (UGC 8308), 4.3 Mpc (UGC 8320), 4.6 Mpc (NGC 5204), and 3.2 Mpc (UGC 8833). The CVn I cloud has a mean radial velocity of 286 +- 9 km/s, a mean distance of 4.1 +- 0.2 Mpc, a radial velocity dispersion of 50 km/s, a mean projected radius of 760 kpc, and a total blue luminosity of 2.2 * 10^{10} L_{\sun}. Assuming virial or closed orbital motions for the galaxies, we estimated their virial and their orbital mass-to-luminosity ratio to be 176 and 88 M_{\sun}/L_{\sun}, respectively. However, the CVn I cloud is characterized by a crossing time of 15 Gyr, and is thus far from a state of dynamical equilibrium. The large crossing time for the cloud, its low content of dSph galaxies ($< 6$ %), and the almost ``primordial'' shape of its luminosity function show that the CVn I complex is in a transient dynamical state, driven rather by the free Hubble expansion than by galaxy interactions.Comment: 23 pages, 6 figures, A&A in preparation. The version does not include Figure 2. High resolution figures 1 and 2 (11311k) are available at http://luna.sao.ru/~sme/figsCVn.tar.g

A Space-based Observational Strategy for Characterizing the First Stars and Galaxies Using the Redshifted 21 cm Global Spectrum

© 2017. The American Astronomical Society. All rights reserved. The redshifted 21 cm monopole is expected to be a powerful probe of the epoch of the first stars and galaxies (10 < z < 35). The global 21 cm signal is sensitive to the thermal and ionization state of hydrogen gas and thus provides a tracer of sources of energetic photons-primarily hot stars and accreting black holes-which ionize and heat the high redshift intergalactic medium (IGM). This paper presents a strategy for observations of the global spectrum with a realizable instrument placed in a low-altitude lunar orbit, performing night-time 40-120 MHz spectral observations, while on the farside to avoid terrestrial radio frequency interference, ionospheric corruption, and solar radio emissions. The frequency structure, uniformity over large scales, and unpolarized state of the redshifted 21 cm spectrum are distinct from the spectrally featureless, spatially varying, and polarized emission from the bright foregrounds. This allows a clean separation between the primordial signal and foregrounds. For signal extraction, we model the foreground, instrument, and 21 cm spectrum with eigenmodes calculated via Singular Value Decomposition analyses. Using a Markov Chain Monte Carlo algorithm to explore the parameter space defined by the coefficients associated with these modes, we illustrate how the spectrum can be measured and how astrophysical parameters (e.g., IGM properties, first star characteristics) can be constrained in the presence of foregrounds using the Dark Ages Radio Explorer (DARE)