ADC/CDS Standard Document for Catalog:
/journal_tables/A+A/309/446/

1. Use the ADC Data Viewer Suite to visualize the data.
2. Get the data files via anonymous FTP. (See Note.)

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      (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-H{alpha} comparison, we have also
    carried out new deep integrations, photometry, and accurate mapping of
    the H{alpha} emission. A catalogue of 478 HII regions in M 51 has been
    established from the analysis of narrow band H{alpha} 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 H{alpha} 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:
    ----------------------------------------------------
     RA (J2000) DE    Name(s)
    ----------------------------------------------------
    13 29.9  +47 12   M 51 = NGC 5194 = Whirlpool galaxy
    ----------------------------------------------------

File Summary:
--------------------------------------------------------------------------------
  FileName      Lrecl  Records   Explanations
--------------------------------------------------------------------------------
ReadMe             80        .   This file
table2             73      478   Large catalogue of the HII regions
                                 observed in M51
--------------------------------------------------------------------------------

Byte-by-byte Description of file: table2
--------------------------------------------------------------------------------
   Bytes Format  Units        Label   Explanations
--------------------------------------------------------------------------------
   7-  9  I3     ---          Source  Source number
  13- 16  A4     ---          CCM     Designation in Carranza et al. 1969
				      (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    ? H{alpha} fluxes (2)
  58- 61  F4.1   arcsec       eDiam   ? Effective diameter, blank if unresolved.
  69- 72  F4.1   arcsec       gDiam   ? Geometrical diameter
--------------------------------------------------------------------------------
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): H{alpha} fluxes are given in units of 10^-16^erg/cm2/s
--------------------------------------------------------------------------------

Courtesy: Henri Petit, Observatoire de Marseille <hpetit@obmara.cnrs-mrs.fr>

References:
   Carranza G., Crillon R., Monnet G. =1969A&A.....1..479C
================================================================================
(End)                                       Simona Mei [CDS]         13-Oct-1995