81,868 research outputs found
A close look into an intermediate redshift galaxy using STIS
We present a detailed view of a galaxy at z=0.4 which is part of a large
database of intermediate redshifts using high resolution images. We used the
STIS parallel images and spectra to identify the object and obtain the
redshift. The high resolution STIS image (0.05'') enabled us to analyse the
internal structures of this galaxy. A bar along the major axis and hot-spots of
star formation separated by 0.37'' (1.6 kpc) are found along the inner region
of the galaxy. The analysis of the morphology of faint galaxies like this one
is an important step towards estimating the epoch of formation of the Hubble
classification sequence.Comment: Astronomy and Astrophysics Letter - accepte
HASH: the Hong Kong/AAO/Strasbourg H-alpha planetary nebula database
By incorporating our major recent discoveries with re-measured and verified
contents of existing catalogues we provide, for the first time, an accessible,
reliable, on-line SQL database for essential, up-to date information for all
known Galactic PNe. We have attempted to: i) reliably remove PN mimics/false
ID's that have biased previous studies and ii) provide accurate positions,
sizes, morphologies, multi-wavelength imagery and spectroscopy. We also provide
a link to CDS/Vizier for the archival history of each object and other valuable
links to external data. With the HASH interface, users can sift, select,
browse, collate, investigate, download and visualise the entire currently known
Galactic PNe diversity. HASH provides the community with the most complete and
reliable data with which to undertake new science.Comment: 8 pages, 4 figures; accepted to appear in refereed proceedings of the
11th Pacific Rim Conference held in Hong-kong in Dec 201
Galaxy Zoo: Morphological Classification and Citizen Science
We provide a brief overview of the Galaxy Zoo and Zooniverse projects,
including a short discussion of the history of, and motivation for, these
projects as well as reviewing the science these innovative internet-based
citizen science projects have produced so far. We briefly describe the method
of applying en-masse human pattern recognition capabilities to complex data in
data-intensive research. We also provide a discussion of the lessons learned
from developing and running these community--based projects including thoughts
on future applications of this methodology. This review is intended to give the
reader a quick and simple introduction to the Zooniverse.Comment: 11 pages, 1 figure; to be published in Advances in Machine Learning
and Data Mining for Astronom
The AMIGA sample of isolated galaxies. XI. Optical characterisation of nuclear activity
Context.- This paper is part of a series involving the AMIGA project
(Analysis of the Interstellar Medium of Isolated GAlaxies), which identifies
and studies a statistically-significant sample of the most isolated galaxies in
the northern sky. Aims.- We present a catalogue of nuclear activity, traced by
optical emission lines, in a well-defined sample of the most isolated galaxies
in the local Universe, which will be used as a basis for studying the effect of
the environment on nuclear activity. Methods.- We obtained spectral data from
the 6th Data Release of the Sloan Digital Sky Survey, which were inspected in a
semi-automatic way. We subtracted the underlying stellar populations from the
spectra (using the software Starlight) and modelled the nuclear emission
features. Standard emission-line diagnostics diagrams were applied, using a new
classification scheme that takes into account censored data, to classify the
type of nuclear emission. Results.- We provide a final catalogue of
spectroscopic data, stellar populations, emission lines and classification of
optical nuclear activity for AMIGA galaxies. The prevalence of optical active
galactic nuclei (AGN) in AMIGA galaxies is 20.4%, or 36.7% including transition
objects. The fraction of AGN increases steeply towards earlier morphological
types and higher luminosities. We compare these results with a matched analysis
of galaxies in isolated denser environments (Hickson Compact Groups). After
correcting for the effects of the morphology and luminosity, we find that there
is no evidence for a difference in the prevalence of AGN between isolated and
compact group galaxies, and we discuss the implications of this result.
Conclusions.- We find that a major interaction is not a necessary condition for
the triggering of optical AGN.Comment: 16 pages, 11 figures, 12 tables, published in Astronomy and
Astrophysics. Figure 5 corrected: [OI] diagram adde
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