A sample of unusually warm IRAS galaxies with spectral energy distributions peaking at 60μm is studied. The complete sample consisting of 21 known galaxies and 40 previously unidentified galaxies is selected according to the following criteria: all galaxies in IRAS Point Source Catalogue with high quality detections at 25μm and 60μm, FIR fluxes such that 4>f 60 /f 25 >1 and f 60 /f 100 >1, and a galactic latitude of |b|>10°. The colour ctireria select against galaxies with a significant cool dust component and the hotter dust present is presumably circumnuclear (Vader et al., 1988). CCD imaging reveals a morphological dichotomy in our sample - the galaxies are either relaxed systems (E/S0) or interacting (double nuclei, tidal features etc.). The relatively fast process of merging may link these two types of systems.
We report the discovery of blue condensations in the exceptionally gas-rich elliptical galaxy NGC 5173. The condensations represent about one percent of the total blue light of the galaxy and have luminosities, sizes, and colors typical of giant H II regions. They appear to be distributed in an off-centered disk that coincides with the neutral hydrogen disk rather than the optical light of the galaxy. The distribution is most suggestive of two tightly wound spiral arms with a radial extent of 3.5 to 9.5 kpc. This is the first time that giant blue condensations on such a large scale have been found in an elliptical galaxy
The optical and infrared luminosity functions are determined for a 60 micron flux-limited sample of 68 IRAS galaxies covering a total area of 150 deg sq. The IR function is in good agreement with that obtained by other authors. The shape of the optical luminosity function is similar to that of optically selected galaxy samples. The integrated light of most objects in the sample have (NII) to H alpha line flux ratios characteristic of HII-region galaxies. In the absolute magnitude range M sub J = -18, -22 about 14% of late-type galaxies are IRAS galaxies. The apparent companionship frequency is about twice as large as that for a comparable sample of non-IRAS late-type galaxies.
view Abstract Citations (37) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS IC 3475 : A stripped dwarf galaxy in the Virgo cluster. Vigroux, L. ; Thuan, T. X. ; Vader, J. P. ; Lachieze-Rey, M. Abstract The authors have obtained B and R CCD and H I observations of the Virgo dwarf galaxy IC 3475. The galaxy is remarkable for its very large diameter (≡10 kpc for a Virgo distance modulus of 31) and is comparable in size to the large dwarfs discussed by Sandage and Binggeli. Its light profile is best fitted by an exponential law, characteristic of a dwarf Magellanic irregular galaxy. Despite possessing the photometric structure of a dwarf Magellanic irregular galaxy, IC 3475 contains less than 5.3×106M_sun; of neutral hydrogen. Its hydrogen mass to blue light ratio is less than 0.01, ≡60 times less than the mean value observed for dwarf Magellanic irregulars. It is most likely that IC 3475, which is located near the core of the Virgo cluster, is a stripped dwarf galaxy. The very large size of the galaxy (its diameter is ≡1.8 times larger than that of "normal" dwarfs) appears to rule out evolution of IC 3475 from a normal dwarf irregular or to a normal dwarf elliptical. Publication: The Astronomical Journal Pub Date: January 1986 DOI: 10.1086/113981 Bibcode: 1986AJ.....91...70V Keywords: Barred Galaxies; Dwarf Galaxies; Galactic Structure; Interstellar Gas; Irregular Galaxies; Virgo Galactic Cluster; Astronomical Photometry; Galactic Evolution; H Lines; Hydrogen Clouds; Neutral Gases; Star Clusters; Astrophysics full text sources ADS | data products NED (4) SIMBAD (3)
A determination is made of the optical luminosity function (OPLF) of an infrared flux-limited sample of IRAS galaxies. The sample includes 92 objects; among these are an infrared-loud quasar and two previously known Seyferts. The OPLF of the IRAS galaxies in the sample shows that in the magnitude range between -22 and 18, IRAS galaxies represent about 15 percent of field galaxies. At low luminosities, Mj greater than -19 mag, there may be a deficiency of IRAS galaxies relative to the field galaxies. The far-IR luminosity function of the sample is also derived; it agrees well with other determinations.
view Abstract Citations (13) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Supergiant Supernova-blown Bubble in the Spiral Galaxy NGC 1620 Vader, J. Patricia ; Chaboyer, Brian Abstract We present OBR and Hα imaging of NGC 1620, a highly inclined spiral galaxy that contains a large scale, arclike feature of radius 3 kpc in its outer disk at a distance of ~11 kpc from the center. What is unusual about this arclike feature is its stellar nature and the presence of a luminous star cluster at its center. The arc is fragmented into H II region complexes and OB star clusters and shows two kinks in optical continuum light. It spans an angle of 220^deg^ on our O image and a full, though fragmented, circle on an unsharp masked R image. It is centered on a young star cluster that is the most luminous clump in blue optical continuum light besides the nucleus of the galaxy. This central star cluster has OBR colors and a surface brightness similar to those of other H II regions, but is a relatively weak Hα emitter. It consists of at least three unresolved condensations in optical continuum light. Its location at the center of the arc and its prominence within the galaxy suggests that it has been the site of several generations of supernova explosions that swept up the surrounding gas into a supershell. When it attained a radius of 0.5-1 kpc, this shell became gravitationally unstable and formed the stars which now delineate the arc. The constraints imposed by the survival of the expanding arc against random stellar motions and the age of the stars in the arc yield a required energy input by a minimum of 400 and a maximum of 6500 supernovae. In this scenario the asymmetry in surface brightness of the arc reflects the radial gradient of the gas density in the disk of NGC 1620, while the kinks reflect inhomogeneities in the original gas distribution with respect to the central star cluster. The supernova superbubble formed at least 5 x 10^7^ yr ago so that, unless supernova explosions continued after the onset of star formation in the expanding shell, the bubble interior has cooled and the corresponding hole in the H I distribution no longer exists. An unsharp masked image reveals the presence of a central bar in NGC 1620 which we therefore reclassify as an SBbc galaxy. Publication: The Astrophysical Journal Pub Date: June 1995 DOI: 10.1086/175731 arXiv: arXiv:astro-ph/9412016 Bibcode: 1995ApJ...445..691V Keywords: Bubbles; Spiral Galaxies; Star Formation; Supergiant Stars; Supernova Remnants; Supernovae; Gaseous Diffusion; H Alpha Line; H Ii Regions; Star Clusters; Stellar Luminosity; Stellar Motions; Astrophysics; GALAXIES: SPIRAL; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 1620; ISM: BUBBLES; ISM: H II REGIONS; ISM: SUPERNOVA REMNANTS; Astrophysics E-Print: 12 pages, AAS LaTeX, postscript file available from: ftp://ftp.cita.utoronto.ca/cita/brian/papers/n1620.ps Figures not included. Hard copy of figures available upon request to: chaboyer@cita.utoronto.ca full text sources arXiv | ADS | data products SIMBAD (2) NED (1)
Description des techniques d'etalonnage et de reduction de donnees utilisees pour le traitement des observations CCD photometriques d'un echantillon de 36 galaxies. Une serie de diagrammes des luminosites, des ellipticites, des angles d'orientation, des contributions bulbe-disque, des diagrammes magnitude couleur et couleur couleur des galaxies observees est donnee
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