J/A+A/309/446 HII Regions in M51 (Petit+, 1996)
The spiral structure of M51 from Halpha and 2000A UV Images.
A new tracer of density waves effects.
Petit H., Hua C.T., Bersier D., Courtes G.
<Astron. Astrophys. 309, 446 (1996)>
=1996A&A...309..446P 1996A&A...309..446P (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ;
Keywords: galaxies: M51 - galaxies: spiral; ISM - ultraviolet: galaxies
Description:
A deeper detection of the spiral structure of the Sbc galaxy M 51 is
the main goal of this paper. New UV data in the 2000A range were
obtained with a high altitude balloon of the Laboratoire d'Astronomie
Spatiale de Marseille and the Observatoire de Geneve, (LAS-OG). The
data reveal the location of hot, evolved low-mass stars predominantly
along the outside edge of, and down stream from, the spiral arms
defined by the string of HII regions. Since these stars have a
relatively well-defined age compared to the "mixed" population of
stars seen in the arms when observed in visible light, the UV data is
well-suited to derive time-scales of spiral arm components. In
particular, the relation between spiral structure and star formation,
which is at least partly due to the density wave shock mechanism, can
be studied from the differential positions of the low-mass stars
observed in the UV and the massive stars coexisting with the ionized
gas. To facilitate such detailed UV-Hα comparison, we have also
carried out new deep integrations, photometry, and accurate mapping of
the Hα emission. A catalogue of 478 HII regions in M 51 has been
established from the analysis of narrow band Hα images taken
with a combination of the Special Astronomical Observatory (SAO)
Russian image tube, and the Observatoire de Marseille (OM) focal
reducer f/1.5 (9m equivalent focal length) attached at the prime focus
of the 6-m telescope of the SAO. The radial and tangential shifts of
the main and secondary spiral structures in UV and Hα are also
compared with other spiral tracers. The displacements observed in
these observations are compatible with a scenario in which the star
formation is triggered by the density wave.
Objects observed:
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RA (J2000) DE Name(s)
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13 29.9 +47 12 M 51 = NGC 5194 = Whirlpool galaxy
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 73 478 Large catalogue of the HII regions
observed in M51
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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7- 9 I3 --- Source Source number
13- 16 A4 --- CCM Designation in Carranza et al. 1969
(1969A&A.....1..479C 1969A&A.....1..479C)
22- 28 F7.2 arcsec Xpos X position (1)
33- 39 F7.2 arcsec Ypos Y position (1)
47- 50 I4 10-19W/m2 Flux ? Hα fluxes (2)
58- 61 F4.1 arcsec eDiam ? Effective diameter, blank if unresolved.
69- 72 F4.1 arcsec gDiam ? Geometrical diameter
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Note (1): The positions of the photometric centre of Halpha emission are
centered on 13 27 46.3 +47 27 10.2 (1950)(source 212);
X axis is oriented toward East and Y axis toward North
Note (2): Hα fluxes are given in units of 10-16erg/cm2/s
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Courtesy: Henri Petit, Observatoire de Marseille
References:
Carranza G., Crillon R., Monnet G. =1969A&A.....1..479C 1969A&A.....1..479C
(End) Simona Mei [CDS] 13-Oct-1995