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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 225829.0, MPI für Astronomie / Publikationen_mpia
HS 0837+4717 - a metal-deficient blue compact
galaxy with large nitrogen excess
Authors:Pustilnik, S.; Kniazev, A.; Pramskij, A.; Izotov, Y.; Foltz, C.; Brosch, N.; Martin, J.-M.; Ugryumov, A.
Date of Publication (YYYY-MM-DD):2004
Title of Journal:Astronomy and Astrophysics
Start Page:469
End Page:484
Review Status:not specified
Audience:Not Specified
Abstract / Description:We present the results of high S/N long-slit
spectroscopy with the Multiple Mirror and the
SAO 6-m telescopes, optical imaging with the
Wise 1-m telescope and H I observations with the
Nan‚‚ccedil;ay Radio Telescope of the very
metal-deficient (12+ log (O/H)=7.64) luminous
(MB= -18.1m) blue compact galaxy (BCG)
HS 0837+4717. The blue bump near ‚‚lambda;4650,
characteristic of WR stars is detected in the
central supergiant H II region, as well as the
barely seen red bump at ‚‚lambda;5808. The
derived number of WR stars in the region of the
current starburst is ‚‚sim;1000. Evidence for
fast motions in this region is also seen as
broad, low-contrast components in the H‚‚alpha;,
H‚‚beta; and strong [O III] lines
‚‚lambda;‚‚lambda;4959,5007. While the extinction
of the narrow emission lines from the supergiant
H II region is low, the very large Balmer
decrement of the broad components suggests that
the part of current starburst is highly obscured
by dust. Abundance ratios X/O for X=Ne, Ar, S,
Fe and Cl in the supergiant H II region are in
good agreement with the mean values of other
very metal-deficient BCGs. Nitrogen, however, is
overabundant by a factor of ‚‚sim;6. This implies
an unusually efficient N enrichment in HS
0837+4717, and probably, a non-typical evolution
scenario. The H‚‚alpha;-line position-velocity
(P-V) diagrams for directions approximately along
the major and minor axes reveal disturbed
motions of the ionized gas, mainly in peripheral
regions. The SW part of the major axis P-V
diagram looks like a rotation curve, with the
velocity amplitude Vrot ‚‚sim;50-70 km
s-1 at r =4.3 kpc. Its NE part
displays, however, strong deviations, indicating
either counter-rotation, or a strong
outflow/supershell. If it is considered as
indicating a shell-like feature its velocity
amplitude of ‚‚sim;70 km s-1 (relative
to the extrapolated rotation curve), and the
apparent extent of ‚‚sim;4 arcsec (3.3 kpc)
imply a dynamical age of ‚‚sim;14 Myr and the
full energetic equivalent of ‚‚sim;2.3‚‚times;
104 SNe. The latter indicates
continuing starbursts during at least this time
interval. The long-slit spectra reveal a complex
morphology for this galaxy. It consists of two
compact regions at a distance of ‚‚sim;2 kpc.
Their continuum flux differs by a factor of
four. The brightest one is related to the
current starburst with the age of ‚‚sim;3.7 Myr.
The slightly redder fainter component could be
an older starburst (‚‚sim;25 Myr). The Wise 1-m
telescope UBVR integrated photometry reveals a
high optical luminosity for this BCG, and the
unusual (B-V) and (V-R) colours. The morphology
of HS 0837+4717 is highly disturbed, with two
small tails emerging to NNW and SSE. Such a
disturbed overall morphology, a
``double-nucleus" structure, significantly
disturbed velocities of ionized gas, together
with the very high power of the starburst
suggests a possible explanation of the object as
a recent merger. We compare the properties of
this BCG and of similar objects known in the
literature, and conclude that their high
nitrogen excess is most probably related to the
short phase of a powerful starburst when many WR
stars contribute to the enrichment of ISM.
Free Keywords:galaxies: starburst; galaxies: abundances;
; galaxies: interactions; galaxies: evolution;
; stars: Wolf-Rayet; galaxies: individual: HS
; 0837+4717
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
External Affiliations:Nizhnij Arkhyz, Karachai-Circassia 369167,
Russia; Isaac Newton Institute of Chile, SAO
Branch), AB(Special Astrophysical Observatory
RAS, Nizhnij Arkhyz, Karachai-Circassia 369167,
Russia; Max Planck Institut f‚‚uuml;r Astronomie,
K‚‚ouml;nigstuhl 17, 69117 Heidelberg, Germany;
Isaac Newton Institute of Chile, SAO Branch),
AC(Special Astrophysical Observatory RAS, Nizhnij
Arkhyz, Karachai-Circassia 369167, Russia; Isaac
Newton Institute of Chile, SAO Branch), AD(Main
Astronomical Observatory, 27 Zabolotnoho str.,
Kyiv 03680, Ukraine), AE(National Science
Foundation, 4201 Wilson Blvd., Arlington,
Virginia 22230, USA), AF(the Wise Observatory and
the Raymond and Beverly Sackler Faculty of Exact
Sciences, Tel-Aviv University, Tel Aviv 69978,
Israel), AG(Observatoire de Paris, place J.
Janssen, 92195 Meudon Cedex, France), AH(Special
Astrophysical Observatory RAS, Nizhnij Arkhyz,
Karachai-Circassia 369167, Russia; Isaac Newton
Institute of Chile, SAO Branch)
Identifiers:URL:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi... [ID No:1]
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