J/A+A/690/A166 Legacy Survey BHB stars (Amarante+ 2024)
Mapping the anisotropic Galactic stellar halo with blue horizontal branch stars.
Amarante J.A.S., Koposov S.E., Laporte C.F.P.
<Astron. Astrophys. 690, A166 (2024)>
=2024A&A...690A.166A 2024A&A...690A.166A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, blue ; Stars, horizontal branch ; Photometry, SDSS
Keywords: techniques: photometric - stars: horizontal-branch - Galaxy: halo -
Galaxy: stellar content - Galaxy: structure
Abstract:
We used Legacy Survey photometric data to probe the stellar halo in
multiple directions of the sky using a probabilistic methodology to
identify Blue Horizontal Branch (BHB) stars. The measured average
radial density profile follows a double power law in the range
5<rgc/kpc<120, with a density break at rgc≃20kpc. This description,
however, falls short, depending on the chosen line-of-sight, with some
regions showing no signature of a break in the profile and a wide
range of density slopes, e.g. outer slope -5.5≲αout≲-4,
pointing towards a highly anisotropic stellar halo. This explains in
part the wide range of density profiles reported in the literature
owing to different tracers and sky coverage. Using our detailed 3-D
stellar halo density map, we quantify the shape of the Pisces
overdensity associated with the transient wake response of the
Galaxy's (dark) halo to the Large Magellanic Cloud (LMC). Measured
in the LMC's coordinate system, Pisces stands above the background,
is 60 degrees long and 25 degrees wide and aligned with the LMC's
orbit. This would correspond to a wake width of ∼32kpc at ∼70kpc. We
do not find a statistically significant signature of the collective
response in density as previously reported in the literature measured
with K giant stars, despite our larger numbers. We release the
catalogue constructed in this study with 95446 possible BHB stars and
their BHB probability.
Description:
We use objects from Legacy Survey Data Release 9 (Dey et. al.,
2019AJ....157..168D 2019AJ....157..168D. to construct a catalogue with 95446 blue
horizontal branch star candidates.
We then construct a catalogue with 95446 objects containing LSDR9
release, brickid and objid. These three parameters provide a unique
identifier hash.
The catalogue also includes "R.A.", "Dec.", the extinction corrected
"g0", "r0", "z0", photometric bands, the colour "grz", the absolute
"Mg" magnitude, and the probability of a stellar object being a BHB
star, "PBHB".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 114 95446 Catalog of blue horizontal branch star candidates
(table C1)
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Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Release LSDR9 releaese
6- 11 I6 --- Brickid brickid
13- 17 I5 --- Objid objid
19- 30 F12.8 deg RAdeg Right ascension (J2000)
32- 43 F12.8 deg DEdeg Declination (J2000)
45- 55 F11.8 mag g0mag Extinction corrected g magnitude
57- 67 F11.8 mag r0mag Extinction corrected r magnitude
69- 79 F11.8 mag z0mag Extinction corrected z magnitude
81- 91 E11.3 mag grz grz colour (1)
93-102 F10.8 mag gMAG Absolute g magnitude
105-114 E10.5 --- PBHB Probability of a stellar object being a BHB star
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Note (1): grz colour defined as
grz = 1.07163(g-r)5 - 1.42272(g-r)4 + 0.69476(g-r)3 - 0.12911(g-r)2
+ 0.66993(g-r) - 0.11368 - (r-z)
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Acknowledgements:
Joao A.S. Amarante, joaoant(at)gmail.com
(End) Patricia Vannier [CDS] 01-Jul-2024