J/ApJ/718/683 The edge of the young Galactic disk (Carraro+, 2010)
The edge of the young Galactic disk.
Carraro G., Vazquez R.A., Costa E., Perren G., Moitinho A.
<Astrophys. J., 718, 683-694 (2010)>
=2010ApJ...718..683C 2010ApJ...718..683C
ADC_Keywords: Clusters, open ; Photometry, UBV ; Stars, OB ; Stars, distances ;
Spectral types ; Stars, early-type
Keywords: Galaxy: disk - Galaxy: structure -
open clusters and associations: general
Abstract:
In this work, we report and discuss the detection of two distant
diffuse stellar groups in the third Galactic quadrant. They are
composed of young stars, with spectral types ranging from late O to
late B, and lie at galactocentric distances between 15 and 20kpc.
These groups are located in the area of two cataloged open clusters
(VdB-Hagen 04 and Ruprecht 30), projected toward the Vela-Puppis
constellations, and within the core of the Canis Major overdensity.
Their reddening and distances have been estimated by analyzing their
color-color and color-magnitude diagrams, derived from deep UBV
photometry. The existence of young star aggregates at such extreme
distances from the Galactic center challenges the commonly accepted
scenario in which the Galactic disk has a sharp cutoff at about 14kpc
from the Galactic center and indicates that it extends to much greater
distances (as also supported by the recent detection of CO molecular
complexes well beyond this distance). While the groups we find in the
area of Ruprecht 30 are compatible with the Orion and Norma-Cygnus
spiral arms, respectively, the distant group we identify in the region
of VdB-Hagen 04 lies in the external regions of the Norma-Cygnus arm,
at a galactocentric distance (∼20kpc) where no young stars have been
detected so far in the optical.
Description:
The regions of interest (see Figure 1) were observed with the Y4KCAM
camera attached to the Cerro Tololo Inter-American Observatory (CTIO)
1.0m telescope, in UBV filter, in 2008 Jan 29,31 and Feb 1,3 for the
two following fields:
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Field Designation R.A. (2000) DEC l b E(B-V) Constellation
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1 VdB-Hagen 04 07:37:44 -36:04:00 249.98 -07.13 0.49 Puppis
2 Ruprecht 30 07:42:25 -31:28:00 246.42 -04.05 0.68 Puppis
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 62 71 Basic properties of the early spectral-type stars
encountered in Field 1 (VdB-Hagen 04)
table4.dat 62 193 Basic properties of the early spectral-type stars
encountered in Field 2 (Ruprecht 30)
vdbh4.dat 55 3957 *List of (XY) positions for all VdB-Hagen 4 stars
rup30.dat 32 6108 *List of (XY) positions for all Ruprecht 30 stars
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Note on vdbh4.dat, rup30.dat: these 2 tables were constructed at CDS, from
the archives of these 2 clusters at WEBDA (http://www.univie.ac.at/webda/)
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See also:
B/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2012)
II/183 : UBVRI Photometric Standards (Landolt 1992)
J/A+A/511/A38 : Open clusters in third galactic quadrant (Vazquez+, 2010)
J/ApJ/672/930 : Distant CO clouds in third galactic quadrant (Vazquez+, 2008)
J/A+A/464/573 : VI photometry of 5 open clusters (Carraro+, 2007)
Byte-by-byte Description of file: table3.dat table4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID [25/6107] Star identifier
6- 10 F5.2 mag Vmag V-band magnitude
12- 16 F5.2 mag B-V B-V color index
18- 22 F5.2 mag U-B U-B color index
24- 28 F5.2 mag E(B-V) B-V color excess
30- 34 F5.2 mag E(B-V)0 B-V color excess; corrected for extinction
36- 40 F5.2 mag E(U-B)0 U-B color excess; corrected for extinction
42- 46 F5.2 mag VMag V-band absolute magnitude
48- 51 A4 --- SpT Photometric MK spectral type
53- 57 F5.2 kpc Dist Distance
59- 62 F4.2 kpc e_Dist Dist uncertainty
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Byte-by-byte Description of file (#): vdbh4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID [1/3957] Star identifier
6- 13 F8.2 pix Xpos CCD position along the X axis
15- 22 F8.2 pix Ypos CCD position along the Y axis
25- 30 F6.3 mag Vmag V-band magnitude
32- 37 F6.3 mag B-V (B-V) color
39- 44 F6.3 mag U-B (U-B) color
46- 49 I4 --- ID07 ? Identifier in Carraro et al. 2007,
Cat. J/A+A/464/573
51- 55 I5 --- WEBDA WEBDA ID (http://www.univie.ac.at/webda)
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Byte-by-byte Description of file (#): rup30.dat
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Bytes Format Units Label Explanations
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2- 5 I4 --- ID [1/6108] Star identifier, as in table3
8- 12 F5.2 mag Vmag V-band magnitude
15- 22 F8.2 pix Xpos CCD position along the X axis
25- 32 F8.2 pix Ypos CCD position along the Y axis
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Nomenclature note:
* Table 3: stars are <[CVC2010] VdB-Hagen 04 NNNN> in the dictionary of
nomenclature.
* Table 4: stars are <[CVC2010] Ruprecht 30 NNNN>.
History:
* 07-Jun-2012: From electronic version of the journal
* 21-Jul-2012: Added (xy) positions from WEBDA
(End) Emmanuelle Perret [CDS] 07-Jun-2012