J/A+A/547/A15 Red supergiants around Stephenson 2 (Negueruela+, 2012)
Red supergiants around the obscured open cluster Stephenson 2.
Negueruela I., Marco A., Gonzalez-Fernandez C., Jimenez-Esteban F.,
Clark J.S., Garcia M., Solano E.
<Astron. Astrophys., 547, A15-15 (2012)>
=2012A&A...547A..15N 2012A&A...547A..15N
ADC_Keywords: Clusters, open ; Stars, giant ; Photometry, infrared ;
Radial velocities
Keywords: stars: evolution - supergiants -
open clusters and associations: individual: Stephenson 2 -
Galaxy: structure - virtual observatory tools
Abstract:
Several clusters of red supergiants have been discovered in a small
region of the Milky Way close to the base of the Scutum-Crux Arm and
the tip of the Long Bar. Population synthesis models indicate that
they must be very massive to harbour so many supergiants. Amongst
these clusters, Stephenson 2, with a core grouping of 26 red
supergiants, is a strong candidate to be the most massive young
cluster in the Galaxy.
Stephenson 2 is located close to a region where a strong over-density
of red supergiants had been found. We explore the actual cluster size
and its possible connection to this over-density.
Taking advantage of Virtual Observatory tools, we have performed a
cross-match between the DENIS, USNO-B1 and 2MASS catalogues to
identify candidate obscured luminous red stars around Stephenson 2,
and in a control nearby region. More than 600 infrared bright stars
fulfill our colour criteria, with the vast majority having a
counterpart in the I band and >400 being sufficiently bright in I to
allow observation with a 4-m class telescope. We observed a subsample
of ∼250 stars, using the multi-object, wide-field, fibre spectrograph
AF2 on the WHT telescope in La Palma, obtaining
intermediate-resolution spectroscopy in the 7500-9000Å range. We
derived spectral types and luminosity classes for all these objects
and measured their radial velocities.
Description:
Observations were carried out with the AutoFib2+WYFFOS (AF2)
multi-object, wide-field, fibre spectrograph mounted on the Prime
Focus of the 4.2m William Herschel Telescope (WHT), in La Palma,
Spain. The observations were taken on the nights of 2009, June 5th (in
service mode) and June 6th-7th (in visitor mode).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 80 233 List of AF2 targets (at William Herschel Telescope)
with usable spectra with their main properties
table3.dat 77 26 List of ISIS targets (Intermediate dispersion
Spectrograph and Imaging System).
--------------------------------------------------------------------------------
See also:
B/denis : The DENIS database (DENIS Consortium, 2005)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJ/671/781 : Red supergiants in Sct-Cru Galactic arm (Davies+, 2007)
Byte-by-byte Description of file: table2.dat table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- 2MASS 2MASS name (HHMMSSss+DDMMSSs)
17 A1 --- n_2MASS [a+] Note (1)
19 A1 --- --- [D]
20- 21 I2 --- DFK [1/39]? ID in Davies et al. 2007ApJ...671..781D 2007ApJ...671..781D
<Cl* Stephenson 2 DFK NN> in Simbad
24- 28 F5.2 mag Jmag J magnitude
30- 33 F4.2 mag e_Jmag rms uncertainty on Jmag
35- 39 F5.2 mag Hmag H magnitude
41- 44 F4.2 mag e_Hmag ? rms uncertainty on Hmag
45 A1 --- l_Hmag [c] c: Hmag is an upper limit
46- 50 F5.2 mag Ksmag Ks magnitude
52- 55 F4.2 mag e_Ksmag rms uncertainty on Ksmag
56 A1 --- l_E(J-Ks) Limit flag on E(J-Ks)
57- 60 F4.2 mag E(J-Ks) J-Ks colour excess
62- 65 I4 km/s Vlsr Local Standard of Rest velocity
67- 78 A12 --- SpType MK spectral type
80 A1 --- n_SpType [b] b: blended source (see Sect. 4)
--------------------------------------------------------------------------------
Note (1): Notes as follows:
a = The JHKs magnitudes are from 2MASS. Spectral types are based solely
on our spectra. The colour excess has been calculated from the
observed (J-Ks) colour and the tabulated intrinsic colour,
after Levesque et al. (2005ApJ...628..973L 2005ApJ...628..973L).
+ = not primary targets and their identifications are based on slit
reconstruction. Such objects felt in the slit by chance and do not
necessarily fulfill the selection criteria.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Negueruela et al., Paper I 2011A&A...528A..59N 2011A&A...528A..59N
(End) Patricia Vannier [CDS] 19-Jan-2013