J/ApJ/854/47 RRab stars of Monoceros Ring & A13 overdensities (Sheffield+, 2018)
A disk origin for the Monoceros Ring and A13 stellar overdensities.
Sheffield A.A., Price-Whelan A.M., Tzanidakis A., Johnston K.V.,
Laporte C.F.P., Sesar B.
<Astrophys. J., 854, 47 (2018)>
=2018ApJ...854...47S 2018ApJ...854...47S
ADC_Keywords: Associations, stellar; Stars, variable; Radial velocities;
Stars, distances; Optical
Keywords: galaxies: interactions; Galaxy: disk; Galaxy: formation; Galaxy: halo;
Galaxy: structure
Abstract:
The Monoceros Ring (also known as the Galactic Anticenter Stellar
Structure) and A13 are stellar overdensities at estimated heliocentric
distances of d∼11kpc and 15kpc observed at low Galactic latitudes
toward the anticenter of our Galaxy. While these overdensities were
initially thought to be remnants of a tidally disrupted satellite
galaxy, an alternate scenario is that they are composed of stars from
the Milky Way (MW) disk kicked out to their current location due to
interactions between a satellite galaxy and the disk. To test this
scenario, we study the stellar populations of the Monoceros Ring and
A13 by measuring the number of RR Lyrae and M giant stars associated
with these overdensities. We obtain low-resolution spectroscopy for RR
Lyrae stars in the two structures and measure radial velocities to
compare with previously measured velocities for M giant stars in the
regions of the Monoceros Ring and A13, to assess the fraction of RR
Lyrae to M giant stars (fRR:MG) in A13 and Mon/GASS. We perform
velocity modeling on 153 RR Lyrae stars (116 in the Monoceros Ring and
37 in A13) and find that both structures have very low fRR:MG. The
results support a scenario in which stars in A13 and Mon/GASS formed
in the MW disk. We discuss a possible association between Mon/GASS,
A13, and the Triangulum-Andromeda overdensity based on their similar
velocity distributions and fRR:MG.
Description:
In this work, we aim to clarify the origins of Mon/GASS and A13 by
looking at their stellar populations. We took low-resolution (R∼2000)
spectra of RR Lyrae stars in the same regions of the Galaxy as the M
giants in these two overdensities.
199 Mon/GASS and 72 A13 target RR Lyrae stars (only RRab-type) were
selected from the Catalina Sky Surveys (CSS; Drake+ 2013, J/ApJ/763/32).
Of these targets, a total of 153 were observed from 2016 February 05
to 11 using the 2.4m Hiltner telescope at MDM Observatory with ModSpec.
Objects:
--------------------------------------------------------------
RA (ICRS) DE Designation(s)
--------------------------------------------------------------
07 58 35 +71 26.6 A13 = [SJM2010] A13
Mon/GASS = NAME Monoceros Stream
--------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 75 156 Properties of RR Lyrae stars
--------------------------------------------------------------------------------
See also:
I/317 : The PPMXL Catalog (Roeser+ 2010)
J/AJ/128/1177 : Galactic stellar abundances (Venn+, 2004)
J/A+A/442/1127 : Library of 2500-10500Å synthetic spectra (Munari+, 2005)
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/ApJ/736/146 : Radial velocities of stars in Bootes I (Koposov+, 2011)
J/ApJ/731/4 : Galactic halo as seen by the CFHTLS (Sesar+, 2011)
J/AJ/144/114 : Radial velocities of 6 field RR Lyrae (Sesar+, 2012)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/ApJ/776/26 : RRab stars in the Orphan stream distances (Sesar+, 2013)
J/ApJ/793/62 : Triangulum-Andromeda stellar properties (Sheffield+, 2014)
J/ApJ/844/L4 : PS1 RRab for tracing outer Virgo overdensity (Sesar+, 2017)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- [DCD2013] CSS identifier (JHHMMSS.s+DDMMSS) (1)
18- 27 F10.6 deg GLON Galactic longitude
29- 37 F9.6 deg GLAT Galactic latitude
39- 42 F4.1 kpc Dist [7/19.5] Heliocentric distance
44- 49 F6.1 km/s HRV [-365/353] Heliocentric radial velocity
51- 56 F6.1 km/s VGSR [-399/252] Galactic standard of rest radial
velocity
58- 61 F4.1 km/s e_VGSR [11/24] Uncertainty in VGSR
63- 66 F4.2 --- Phase [0.07/0.8] Observed phase
68- 75 A8 --- Reg Stellar overdensity name (A13 or Mon/GASS)
--------------------------------------------------------------------------------
Note (1): The RR Lyrae were selected from the Catalina Sky Survey (CSS;
http://nesssi.cacr.caltech.edu/DataRelease/) -
see also Drake+, 2013, J/ApJ/763/32 ;
RR Lyrae stars are <[DCD2013] CSS JHHMMSS.s+DDMMSS> in Simbad.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Nov-2018