J/ApJ/831/165 RR Lyrae as tracers in the Virgo overdensity region (Vivas+, 2016)
Disentangling the Virgo overdensity with RR Lyrae stars.
Vivas A.K., Zinn R., Farmer J., Duffau S., Ping Y.
<Astrophys. J., 831, 165-165 (2016)>
=2016ApJ...831..165V 2016ApJ...831..165V (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Radial velocities ; Surveys ; Stars, distances ;
Photometry, VRI
Keywords: stars: variables: RR Lyrae; Galaxy: halo;
stars: kinematics and dynamics; Galaxy: structure
Abstract:
We use a combination of spatial distribution and radial velocity to
search for halo substructures in a sample of 412 RR Lyrae stars
(RRLSs) that covers a region of ∼525 square degrees of the Virgo
overdensity (VOD) and spans distances from the Sun from 4 to 75kpc.
With a friends-of-friends algorithm we identified six
high-significance groups of RRLSs in phase space, which we associate
mainly with the VOD and with the Sagittarius stream. Four other groups
were also flagged as less significant overdensities. Three
high-significance and three lower-significance groups have distances
between ∼10 and 20kpc, which places them in the distance range
attributed by others to the VOD. The largest of these is the Virgo
stellar stream at 19kpc, which has 18 RRLSs, a factor of two increase
over the number known previously. While these VOD groups are distinct
according to our selection criteria, their overlap in position and
distance and, in a few cases, similarity in radial velocity are
suggestive that they may not all stem from separate accretion events.
Even so, the VOD appears to be caused by more than one overdensity.
The Sagittarius (Sgr) stream is a very obvious feature in the
background of the VOD at a mean distance of 44kpc. Two additional
high-significance groups were detected at distances >40kpc. Their
radial velocities and locations differ from the expected path of the
Sgr debris in this part of the sky, and they are likely to be remnants
of other accretion events.
Description:
In addition to the SDSS spectra, several RR Lyrae stars (RRLSs) were
observed by our team with the 4.1m Southern Astrophysical Research
(SOAR; 3500-6160Å) (Cerro Pachon, Chile) and the 3.5m Wisconsin
Indiana Yale and NOAO (WIYN; 4000-6800Å at 4.6Å resolution)
(Kitt Peak, USA) telescopes. Six RRLSs were observed with SOAR in 2014
February and March. 26 additional RRLSs were observed with WIYN in
2011 January.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 67 423 Heliocentric radial velocity for the RR Lyrae
stars from individual SDSS DR12 spectra
table2.dat 48 6 Heliocentric Hbeta and Hgamma radial velocity
for the RR Lyrae stars observed with
the SOAR telescope
table3.dat 48 49 Heliocentric Halpha, Hbeta and Hgamma radial
velocity for the RR Lyrae stars observed
with the WIYN telescope
table4.dat 91 412 Position, light curve parameters, distance and
radial velocity for the RR Lyrae stars
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See also:
III/176 : RR Lyrae Metallicities (Layden 1994)
J/ApJ/816/80 : The SEGUE K giant survey. III. Galactic halo (Janesh+, 2016)
J/MNRAS/446/2251 : Southern Catalina Survey type-ab RR Lyrae (Torrealba+, 2015)
J/ApJ/808/11 : RR Lyrae stars in M4. II. Spitzer/IRAC phot. (Neeley+, 2015)
J/ApJS/213/9 : Catalina Surveys periodic variable stars (Drake+, 2014)
J/ApJ/781/22 : Region I of La Silla QUEST RR Lyrae star survey (Zinn+, 2014)
J/A+A/566/A118 : A comprehensive view of Virgo stellar stream (Duffau+, 2014)
J/MNRAS/441/1230 : RRLyr stars in the Catalins Sky Survey (CS2) (Abbas+, 2014)
J/ApJ/776/26 : RRab stars in the Orphan stream distances (Sesar+, 2013)
J/ApJ/765/154 : RR Lyrae stars in the Catalina Sky Survey (Drake+, 2013)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/AJ/146/21 : LINEAR. II. Catalog of RR Lyrae stars (Sesar+, 2013)
J/AJ/144/114 : Radial velocities of 6 field RR Lyrae (Sesar+, 2012)
J/AJ/140/1337 : RV of 111 Galactic halo stars in Virgo (Brink+, 2010)
J/AJ/139/59 : Milky Way halo velocity dispersion profile (Brown+, 2010)
J/MNRAS/398/1757 : RR Lyraes in SDSS stripe 82 (Watkins+, 2009)
J/ApJ/691/306 : Photom. of RR Lyrae candidates in Virgo stream (Prior+, 2009)
J/AJ/136/1645 : Spectroscopy of bright QUEST RR Lyrae stars (Vivas+, 2008)
J/AJ/132/714 : QUEST RR Lyrae survey. II. Halo overdensities (Vivas+, 2006)
J/AJ/127/1158 : QUEST RR Lyrae Survey first catalog (Vivas+, 2004)
http://www.sdss3.org/ : SDSS-III home page
http://www.lpl.arizona.edu/css/ : Catalina Sky Survey home page
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- PhSurv Photometric Survey where the RR Lyrae star
was catalogued (G1)
8- 27 A20 --- ID ID of the RR Lyrae star in
the Photometric Survey (G2)
29- 34 A6 --- SpSurv SDSS spectroscopic survey (boss, sdss or segue1)
36- 48 F13.5 d HJD Heliocentric Julian Date of the spectrum
at mid-exposure
50- 55 F6.1 s Exp [900/6902] Exposure Time of the spectrum
57- 62 F6.1 km/s HRV [-196/383] Heliocentric radial velocity
64- 67 F4.1 km/s e_HRV [1/30] Error in the heliocentric radial velocity
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- PhSurv Photometric Survey where the RR Lyrae star
was catalogued (G1)
5- 7 A3 --- ID ID of the RR Lyrae star in the
Photometric Survey
9- 21 F13.5 d HJD Heliocentric Julian Date of the spectrum
at mid-exposure
23- 26 I4 s Exp [900/3600] Exposure Time of the spectrum
28- 32 F5.1 km/s HRV(Hb) [30/325] Heliocentric radial velocity measured
at the Balmer line Hβ
34- 37 F4.1 km/s e_HRV(Hb) [10/32] Error in HRV(Hb)
39- 43 F5.1 km/s HRV(Hg) [-23/363] Heliocentric radial velocity measured
at the Balmer line Hγ
45- 48 F4.1 km/s e_HRV(Hg) [15/43] Error in HRV(Hg)
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- PhSurv Photometric Survey where the RR Lyrae star
was catalogued (G1)
5- 8 A4 --- ID ID of the RR Lyrae star in the
Photometric Survey (G2)
10- 22 F13.5 d HJD Heliocentric Julian Date of the spectrum
at mid-exposure
24- 27 I4 s Exp [900/2700] Exposure Time of the spectrum
29- 34 F6.1 km/s HRV(Ha) [-201/321] Heliocentric radial velocity measured
at the Balmer line Hα
36- 41 F6.1 km/s HRV(Hb) [-196/326] Heliocentric radial velocity measured
at the Balmer line Hβ
43- 48 F6.1 km/s HRV(Hg) [-170/294]? Heliocentric radial velocity measured
at the Balmer line Hγ
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- PhSurv Photometric Survey where the RR Lyrae star
was catalogued (G1)
8- 27 A20 --- ID ID of the RR Lyrae star in the
Photometric Survey (G2)
29- 37 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
39- 46 F8.5 deg DEdeg Declination in decimal degrees (J2000)
48- 49 A2 --- Type Type of RR Lyrae star ("ab": 271 stars or
"c": 141 stars)
51- 55 F5.2 mag Vmag [13.6/20.1] Mean magnitude in the V-band
57- 63 F7.5 d Per [0.2/0.9] Period
65- 68 F4.2 mag VAmp [0.1/1.5] Amplitude in the V-band
70- 73 F4.1 kpc Dist [4/77] Distance from the Sun
75 I1 -- Nsp [1/6] Number of spectra used to derive
the radial velocity
77- 80 I4 km/s HRV [-205/400] Heliocentric systemic radial velocity
82- 85 I4 km/s Vgsr [-292/301] Systemic velocity in the
galactic standard of rest
87- 88 I2 km/s e_Vgsr [2/42] Error in the systemic velocity
90- 91 I2 --- Group [1/10]? Group to which the star belongs (1)
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Note (1): Group defined in table 5 as follows:
------------------------------------------------------------
Group|<Vgsr>|<Dist>|Nmb|Symbol/color in Figure 8
(km/s) (kpc)
------------------------------------------------------------
High-significance groups
------------------------------------------------------------
1| -41.3| 44.7|113|triangles/red
2| 135.2| 18.9| 18|circles/green
3| -84.8| 10.4| 7|squares/orange
4| 184.2| 12.4| 5|upside-down triangles/blue
5| 109.4| 47.4| 3|diamonds/green
6| -30.7| 56.4| 3|asterisks/blue
------------------------------------------------------------
Low-significance groups
------------------------------------------------------------
7| 5.4| 29.2| 6|open squares/green
8|-130.9| 17.0| 4|open circles/red
9| 97.7| 10.7| 4|open triangles/orange
10| -93.1| 9.6| 3|open diamonds/black
------------------------------------------------------------
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Global notes:
Note (G1):
LSQ = La Silla-QUEST survey, Zinn+ 2014, J/ApJ/781/22;
<[ZHV2014] NNNN> in Simbad (Nos 1 to 1378).
QUEST = Vivas+, 2004, J/AJ/127/1158; <[VZA2004] NNN> in Simbad;
see also Duffau+, 2014, J/A+A/566/A118; <[DVZ2014] NNN> in Simbad.
CRTS = the Catalina Real-Time Transient Survey, Drake+ 2013, J/ApJ/763/32;
2013, J/ApJ/765/154 and 2014, J/ApJS/213/9;
<[DCD2013] CSS JHHMMSS.s+DDMMSS> or
in Simbad.
LINEAR = the Lincoln Near-Earth Asteroid Research program,
Sesar+ 2013, J/AJ/146/21; in Simbad.
The asterisk in LINEAR 3384231* (tables 1 and 4) indicates that
the star is also in Palaversa+, 2013, J/AJ/146/101
SEKBO = the Southern Edgeworth-Kuiper Belt Object (SEKBO) survey,
Prior+, 2009, J/ApJ/691/306; <[KMP2008] NNNNNN.NNNNN> in Simbad.
Note (G2): LSQ number IDs after #798 in tables 1, 3 and 4 have been converted
by CDS to NNNN-1 to match the numbering in Zinn+, 2014, J/ApJ/781/22
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History:
From electronic version of the journal
05-Apr-2017: Insert into VizieR
16-Jun-2017: Corrections for LSQ numbers in tables 1, 3 and 4 (see Note G2)
Acknowledgments:
Kathy Vivas [Cerro Tololo Inter-American Observatory; ctio.naoa.edu]
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Feb-2017