16 research outputs found
Multicolor photometry of ten Seyfert 1 galaxies
We present BVI photometry of ten Seyfert 1 galaxies and narrow band H-alpha
images for six of these objects as well. The results indicate that the
luminosity sample distribution has an amplitude of almost 4 magnitudes with an
average of M_B=-20.7. The observed morphologies are confined to early type
galaxies. A barred structure is found in only 2 objects. Despite that early
morphological types are dominant in this sample, integrated (B-V) colors are
very blue. For instance, the SO galaxies show, on average, a (B-V)=0.78. This
effect seems to be caused by the luminosity contribution of the active nucleus
and/or the disk to the total luminosity of the galaxy. In the B band, the
contribution of the active galactic nucleus to the total luminosity of the
galaxy varies from 3% to almost 60% and the bulge to disk luminosity ratio
(L_bulge/L_disk) ranges from 0.6 to 22. Signs of tidal interactions seems to be
a common characteristic since they are observed in 6 of the objects and one of
them seems to be located in a poor cluster not yet identified in the
literature. H_alpha extended emission is rare, with only 1 galaxy showing clear
evidence of it. Luminosity profile decomposition shows that the model Gauss +
bulge + disk properly reproduces the surface brightness of the galaxies.
However, in order to account for the luminosity profile, most of the disk
galaxies needs the inner truncated exponential form with a central cutoff
radius ranging from 3 to 10 kpc. This is interpreted in terms of reddened
regions that are well identified in the B-V color maps. These regions present
very similar colors among them, with (B-V)~1.2. This fact could be associated
to the presence of dust confined in the inner regions of the galaxies.Comment: 14 pages, 25 figures. Accepted to Astronomy & Astrophysic
New Probable Dwarf Galaxies in Northern Groups of the Local Supercluster
We have searched for nearby dwarf galaxies in 27 northern groups with
characteristic distances 8-15 Mpc based on the Second Palomar Sky Survey
prints. In a total area of about 2000 square degrees, we have found 90
low-surface-brightness objects, more than 60% of which are absent from known
catalogs and lists. We have classified most of these objects (~80%) as
irregular dwarf systems. The first 21-cm line observations of the new objects
with the 100-m Effelsberg radio telescope showed that the typical linear
diameters (1-2 kpc), internal motions (30 km/s), and hydrogen masses
(~2*10^7M_sun) galaxies correspond to those expected for the dwarf population
of nearby groups.Comment: 8 pages, 1 fugur
Sample of minor merger of galaxies: Optical CCD surface photometry and HII region propertie
We present the results of the B, V and I photometry of eleven southern minor
mergers. The total apparent B magnitude, integrated B-V and V-I colours were
measured. We built B, V, and I equivalent profiles for each galaxy and
decomposed them into bulge and disk components when possible. From
H+N[II] images we have estimated the basic photometric parameters of
the HII regions, such as position, size, B-V and V-I colours, H+[NII]
luminosity and equivalent width. We found a linear
correlation between the luminosity ratios of the components and their ratio of
major diameters, leading to mass ratios between 0.04 0.2, suggesting indeed that our sample is formed by
minor mergers. Most of the HII regions and evolved star-forming regions of the
sample were formed between 3.6 to 13.7 Myr ago with an average of (6.30.7)
Myr. The HII region properties, luminosity, sizes and ages are similar in both
components. The HII regions have log(H+[NII]) luminosity between 38.6
and 41.7. The HII region luminosity function for the whole sample fits a power
law of index = --1.33. The linear correlation between the luminosity
(H+[NII]) and the size of the HII regions has slope of
2.120.06. We found that the disk of the primary component is more luminous
than those of Lu's sample, while the disk of the secondary is smaller and
fainter.Comment: 28 pages, 19 figures, recently accepted for publication in Astronomy
and Astrophysic
XMM-Newton X-ray and Optical Monitor far UV observations of NGC 7070A and ESO 2400100 shell galaxies
We present XMM-Newton X-ray observations of two shell galaxies, NGC 7070A and
ESO 2400100, and far UV observations obtained with the Optical Monitor for
these and for an additional shell galaxy, NGC 474, for which we also have near
and far UV data from GALEX. We aim at gaining insight on the overall evolution
traced by their star formation history and by their hot gas content. The X-ray
and the far UV data are used to derive their X-ray spatial and spectral
characteristics and their UV luminosity profiles. We use models developed ad
hoc to investigate the age of the last episode of star formation from the (UV -
optical) colors and line strength indices. The X-ray spatial and spectral
analysis show significant differences in the two objects. A low luminosity
nuclear source is the dominant component in NGC 7070A log L_X=41.7 erg s^{-1}
in the 2-10 keV band. In ESO 2400100, the X-ray emission is due to a low
temperature plasma with a contribution from the collective emission of
individual sources. In the Optical Monitor image ESO 2400100 shows a double
nucleus, one bluer than the other. This probably results from a very recent
star formation event in the northern nuclear region. The extension of the UV
emission is consistent with the optical extent for all galaxies, at different
degrees of significance in different filters. The presence of the double
nucleus, corroborated by the (UV - optical) colors and line strength indices
analysis, suggests that ESO 2400100 is accreting a faint companion. We explore
the evolution of the X-ray luminosity during accretion processes with time. We
discuss the link between the presence of gas and age, since gas is detected
either before coalescence or several Gyr (>3) after (Abridged).Comment: 17 pages, 11 figures, accepted for publication in A&
A Behavior Model for Next Generation Test Systems
Defining information required by automatic test systems frequently involves a description of system behavior. To facilitate capturing the required behavior information in the context of testing, a formal model of behavior was developed for use by test systems. The approach taken in defining the behavior model was based on information modeling and was derived from recent work in formal methods by the hardware and software design communities. Specifically, an information model was developed in EXPRESS capturing the relationships between essential entities characterizing behavior. In this paper, we provide a high level description of the behavior information model and several examples applying the model in a test environment. INTRODUCTION Defining information required by automatic test systems frequently involves a description of system behavior in one way or another. Behavior is a characteristic of an entity that describes how that entity acts or reacts within some context or environme..