212 research outputs found
Observations of the nucleus of M100
No full textThe galaxy M100 = NGC 4321 is a spiral galaxy in which a bright Type II Supernova was discovered on April 19, 1979. Its spectral evolution was followed with IUE for more than two months (refs. 1,2). At all epochs, the spectrum was dominated by continuous radiation on which emission and absorption features were superimposed. The equivalent width of most of the absorption features appeared not to vary with time suggesting that they originated in the interstellar media of M100 and our own galaxy
Coordinated ground-based and International Ultraviolet Explorer (IUE) observations of hot stars in the Magellanic Clouds
No full textA survey of the ISM in early-type galaxies. I. The ionized gas.
No full textWe present results of a CCD optical imaging survey of the ionized gas in 73
luminous elliptical and lenticular galaxies, selected from the RC3 catalog to
represent a broad variety of X-ray, radio, infrared and kinematical properties.
For each galaxy we have used broad-band R images and narrow-band
images centered at the and emission lines to derive the luminosity
and distribution of the ionized gas.
We found that a large fraction of E (72%) and S0 (85%) galaxies in our
sample contain ionized gas. The gas morphology appears to be rather smooth
for most galaxies; however of the sample galaxies show a very
extended filamentary structure. According to the morphology and size of the
gas distribution, the galaxies have been classified into three broad groups,
named small disk (SD), regular extended (RE) and filamentary structure (F).
The mean diameter of the emitting region ranges between 1 and 10 kpc;
the derived mass of the ionized gas ranges between 103 and 105 solar
masses.
A significant correlation between and X-ray luminosities is
found for those galaxies (27% of the sample) for which we have detected
ionized gas and are also listed as X-ray sources. However, there are
relatively strong X-ray emitting galaxies for which we have not detected
emission and objects which show emission-lines but are not listed
either in the EINSTEIN or in the ROSAT databases.
The distribution of datapoint and upper limits in this diagram suggests that
galaxies with warm gas are also X-ray emitters, while there are X-ray
emitters without measurable emission.
Similar characteristics are present in the correlation between the infrared
luminosity in the 12 band and ; correlations with other
infrared wavelengths are weaker.
A strong correlation was also found between the luminosity
and the luminosity in the B band inside the region occupied by the
line-emitting gas.
We use these correlations to discuss the possible mechanisms
responsible for the gas ionization and excitation, analyzing in particular
the role of the post-AGB stars and the thermal conduction from the X-ray
halo in providing the necessary source of ionization
The Bright and the Dark Side of Malin 1
No full textMalin 1 has long been considered a prototype giant, dark matter dominated Low Surface Brightness galaxy. Two recent studies, one based on a re-analysis of VLA HI observations and the other on an archival Hubble I-band image, throw a new light on this enigmatic galaxy and on its dark/luminous matter properties
The interaction between jets and clouds in the 3CR galaxies
No full textFrom the HST/WFPC2 3CR Snapshot Survey, data taken with the filter F555W, F702W and narrow-ramp, a set of galaxies with noticeable extended structure were selected (e.g. 3C 79, 3C 135, 3C 234, etc). All of these objects show large regions of [OIII] λ 5007˚A emission (narrow ramp filter) and the broad-band filters data show similar structures indicating the presence of strong emission in several lines over these regions. The morphology observed seems to be related (e.g. same position angle, direct overlapping or similar shape) with the radio-jet. For some candidates with these properties GMOS/Gemini spectroscopy was taken. These data (both HST direct imaging and Gemini spectroscopy) can be tested with diagnostic diagrams and total UV photons budget to understand the source of energy that is ionizing the gas. This source of ionization was commonly believed to be the UV photons emitted by the powerful active galactic nuclei (AGN), but several of these objects show clearly that shocks produced by the radio jet are the main cause of the observed gas line emission. We show in this work, the results obtained over some of these radio-galaxies: 3C 135, 3C 180, 3C 234 and 3C 284.Fil: Hägele, G. F.. Universidad Autónoma de Madrid; EspañaFil: Feinstein Baigorri, Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Macchetto, D. F.. Space Telescope Science Institute; Estados UnidosFil: Montero, F.. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin
Stellar disks and embedded bars in early-type galaxies
No full textWe present photometric disk-bulge
decompositions of 28 southern early-type galaxies with types in
either the
RC3 or ESO-Lauberts & Valentijn catalogues.
The
decomposition method applied here is based on that
developed by Scorza & Bender (1995) but the improved version allows
for arbitrary surface brightness profiles of the disk models.
We find three types of objects in this sample:
bulge-dominated systems, with fully embedded close to edge-on disks;
disk-dominated close to edge-on objects and
objects with barred disks being modestly inclined down to face-on.
Like in Scorza & Bender (1995), the analysis made here indicates
that the superposition of a thin disk and an elliptical bulge can give
good account for the morphology of most of the galaxies. We find the
disks to have a diversity of surface brightness profiles, the most
frequent case being that of a disk with an exponential profile, which
becomes steeper at small radii. After disk subtraction, the bulges
follow more closely the law.
Five of the galaxies show signatures of embedded bar components.
These have flat
surface brightness profiles at small radii and rectangular shape, which are
typical features of barred early-type galaxies.
We find that the properties of the galaxies, most notably the
disk-to-total ratio, correlates only modestly with the original
classification of the galaxies
- …
