J/ApJ/795/108 Stellar populations in the Magellanic bridge (Skowron+, 2014)
OGLE-ING the Magellanic system: stellar populations in the Magellanic bridge.
Skowron D.M., Jacyszyn A.M., Udalski A., Szymanski M.K., Skowron J.,
Poleski R., Kozlowski S., Kubiak M., Pietrzynski G., Soszynski I., Mroz P.,
Pietrukowicz P., Ulaczyk K., Wyrzykowski L.
<Astrophys. J., 795, 108 (2014)>
=2014ApJ...795..108S 2014ApJ...795..108S (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Populations, stellar ; Stars, giant
Keywords: Magellanic Clouds - stars: general - stars: statistics - surveys
Abstract:
We report the discovery of a young stellar bridge that forms a
continuous connection between the Magellanic Clouds. This finding is
based on number density maps for stellar populations found in data
gathered by OGLE-IV that fully cover over 270 deg2 of the sky in the
Magellanic Bridge area. This is the most extensive optical survey of
this region to date. We find that the young population is present
mainly in the western half of the MBR, which, together with the newly
discovered young population in the eastern Bridge, form a continuous
stream of stars connecting both galaxies along δ~-73.5 deg.
The young population distribution is clumped, with one of the major
densities close to the SMC and the other fairly isolated and located
approximately mid-way between the Clouds, which we call the OGLE
island. These overdensities are well matched by H I surface density
contours, although the newly found young population in the eastern
Bridge is offset by ∼2 deg north from the highest H I density contour.
We observe a continuity of red clump stars between the Magellanic
Clouds which represent an intermediate-age population. Red clump stars
are present mainly in the southern and central parts of the Magellanic
Bridge, below its gaseous part, and their presence is reflected by a
strong deviation from the radial density profiles of the two galaxies.
This may indicate either a tidal stream of stars, or that the stellar
halos of the two galaxies overlap. On the other hand, we do not
observe such an overlap within an intermediate-age population
represented by the top of the red giant branch and the asymptotic
giant branch stars. We also see only minor mixing of the old
populations of the Clouds in the southern part of the Bridge,
represented by the lowest part of the red giant branch.
Description:
The current, fourth phase of the OGLE survey (OGLE-IV) started in
2010 March with the commissioning of a large new-generation 256
Megapixel 32 chip mosaic camera. The Galactic bulge and disk, the
Magellanic Clouds, and the Magellanic Bridge, including vast areas
around them, are the primary observing targets for the OGLE-IV survey.
Regular monitoring of the selected sky regions by the OGLE survey is
carried out with the 1.3 m Warsaw telescope located at the Las
Campanas Observatory in Chile (operated by the Carnegie Institution
for Science). The field of view of the camera is 1.4 deg2 with a pixel
size of ∼0.26''. The magnitude range of the standard OGLE survey is
approximately 12-21 mag in the I band and 12.5-21.5 mag in the V band.
Objects:
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RA (ICRS) DE Designation(s)
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03 11 -77.5 Magellanic Bridge = NAME Magellanic Bridge
05 23 34.6 -69 45 22 Large Magellanic Cloud = NAME LMC
00 52 38.0 -72 48 01 Small Magellanic Cloud = NAME SMC
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 56 754 Number densities for three stellar populations:
the young population (YP), the red clump (RC),
and the red giant branch (RGB) stars
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See also:
I/244 : OGLE General Catalog of Stars. I. (Szymanski+ 1996)
J/A+A/551/A78 : The Magellanic Bridge Catalogue of Stars - MBCS
(Bagheri+, 2013)
J/AcA/63/1 : OGLE-IV Magellanic Bridge Data supernovae (Kozlowski+, 2013)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 F6.4 h RAhour Hour of Right Ascension (J2000)
8- 14 F7.3 deg DEdeg Declination in decimal degrees (J2000)
16- 22 F7.3 deg GLON Galactic longitude
24- 30 F7.3 deg GLAT Galactic latitude
32- 35 I4 deg-2 YP Young Population star number density (1)
37- 41 I5 deg-2 RC Red Clump star number density (1)
43- 45 I3 deg-2 RGBtop Top Red Giant Branch star number density (1)
47- 50 I4 deg-2 RGBmid Middle Red Giant Branch star number density (1)
52- 56 I5 deg-2 RGBlow Bottom Red Giant Branch star number density (1)
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Note (1): Median background levels are 1±6 stars/deg2 for the YP,
36±25 stars/deg2 for the RC, 16±12 stars/deg2 for
the top RGB (I<16 mag), 63±45 stars/deg2 for the middle
RGB (16 mag<I<19 mag), and 112±65 stars/deg2 for the
bottom RGB region (I>19 mag).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 22-May-2017