291 research outputs found
Global velocity field and bubbles in the BCD Mrk86
We have studied the velocity field of the Blue Compact Dwarf galaxy Mrk86
(NGC2537) using data provided by 14 long-slit optical spectra. This kinematical
information is complemented with narrow-band ([OIII]5007A and Halpha) and
broad-band (B, V, Gunn-r and K) imaging. The analysis of the galaxy global
velocity field suggests that the ionized gas could be distributed in a rotating
inclined disk, with projected central angular velocity of Omega=34 km/s/kpc.
The comparison between the stellar, HI and modeled dark matter density profile,
indicates that the total mass within its optical radius is dominated by the
stellar component. Peculiarities observed in its velocity field can be
explained by irregularities in the ionized gas distribution or local motions
induced by star formation. Kinematical evidences for two expanding bubbles,
Mrk86-B and Mrk86-C, are given. They show expanding velocities of 34 km/s and
17 km/s, Halpha luminosities of 3x10^38 erg/s and 1.7x10^39 erg/s, and physical
radii of 374 and 120 pc, respectively. The change in the [SII]/Halpha,
[NII]/Halpha, [OII]/[OIII] and [OIII]/Hbeta line ratios with the distance to
the bubble precursor suggests a diminution in the ionization parameter and, in
the case of Mrk86-B, an enhancement of the shock-excited gas emission. The
optical-near-infrared colours of the bubble precursors are characteristic of
low metallicity star forming regions (0.2 Zsun) with burst strengths of about 1
per cent in mass.Comment: 14 pages, 12 PostScript figures, accepted for publication in MNRAS,
also available at ftp://cutrex.fis.ucm.es/pub/OUT/gil/PAPERS
Optical photometry of the UCM Lists I and II
We present Johnson B CCD photometry for the whole sample of galaxies of the
Universidad Complutense de Madrid (UCM) Survey Lists I and II. They constitute
a well-defined and complete sample of galaxies in the Local Universe with
active star formation. The data refer to 191 S0 to Irr galaxies at an averaged
redshift of 0.027, and complement the already published Gunn r, J and K
photometries. In this paper the observational and reduction features are
discussed in detail, and the new colour information is combined to search for
clues on the properties of the galaxies, mainly by comparing our sample with
other surveys.Comment: 14 pages, 7 PostScript figures, accepted for publication in A&AS,
also available vi ftp at ftp://cutrex.fis.ucm.es/pub/OUT/pag/PAPERS
Mapping the star formation history of Mrk86: I. Data and models
We have obtained optical (BVR, [OIII]5007 and Halpha), near infrared (JHK)
imaging and long-slit optical spectroscopy for the Blue Compact Dwarf galaxy
Mrk86 (NGC2537). In this paper, the first of two, we present optical-near-
infrared colors and emission-line fluxes for the currently star-forming
regions, intemediate aged starburst and underlying stellar population. We also
describe the evolutionary synthesis models used in Paper II. The R and Halpha
luminosity distributions of the galaxy star-forming regions show maxima at
M_R=-9.5 and L_Halpha=10^37.3 erg s^-1. The underlying stellar population shows
an exponential surface brigthness profile with central value, mu_E,0=21.5 mag
arcsec^-2, and scale, alpha=0.88 kpc, both measured in the R-band image. In the
galaxy outer regions, dominated by this component, no significant color
gradients are observed. Finally, a set of evolutionary synthesis models have
been developed, covering a wide range in metallicity and burst strength.Comment: 21 pages, 14 figures, 2 landscape tables, accepted for publication in
Astronomy & Astrophysics Supplement Series, for higher resolution images see
ftp://cutrex.fis.ucm.es/pub/OUT/gil/PAPERS/aa00_I.ps.g
Optical photometry of the UCM Lists I and II. II-B band surface photometry and morphological discussion
We present Johnson B surface photometry for the UCM Survey galaxies.
One-dimensional bulge-disk decomposition is attempted, discussing on fitting
functions and computational procedures. The results from this decomposition,
jointly with concentration indices and an asymmetry coefficient, are employed
to study the morphological properties of these galaxies. We also compare our
results with the previous morphological classification established using Gunn r
imaging data and with other samples of galaxies. No major statistical
differences in morphology are found between red and blue data, although some
characteristics such as size and luminosity concentration vary. We find a
correlation between luminosity and size. Several parameters are used to
segregate the objects according to their morphological type.Comment: 19 pages, 20 PostScript figures, accepted for publication in A&A,
also available via anonymous ftp at
ftp://cutrex.fis.ucm.es/pub/OUT/pag/PAPERS/AA0
Light pollution offshore: Zenithal sky glow measurements in the mediterranean coastal waters
Light pollution is a worldwide phenomenon whose consequences for the natural environment and the human health are being intensively studied nowadays. Most published studies address issues related to light pollution inland. Coastal waters, however, are spaces of high environmental interest, due to their biodiversity richness and their economical significance. The elevated population density in coastal regions is accompanied by correspondingly large emissions of artificial light at night, whose role as an environmental stressor is increasingly being recognized. Characterizing the light pollution levels in coastal waters is a necessary step for protecting these areas. At the same time, the marine surface environment provides a stage free from obstacles for measuring the dependence of the skyglow on the distance to the light polluting sources, and validating (or rejecting) atmospheric light propagation models. In this work we present a proof-of-concept of a gimbal measurement system that can be used for zenithal skyglow measurements on board both small boats and large vessels under actual navigation conditions. We report the results obtained in the summer of 2016 along two measurement routes in the Mediterranean waters offshore Barcelona, travelling 9 and 31.7Âżkm away from the coast. The atmospheric conditions in both routes were different from the ones assumed for the calculation of recently published models of the anthropogenic sky brightness. They were closer in the first route, whose results approach better the theoretical predictions. The results obtained in the second route, conducted under a clearer atmosphere, showed systematic differences that can be traced back to two expected phenomena, which are a consequence of the smaller aerosol content: the reduction of the anthropogenic sky glow at short distances from the sources, and the slower decay rate of brightness with distance, which gives rise to a relative excess of brightness at large distances from the coastlinePeer ReviewedPostprint (author's final draft
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