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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 (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:
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
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
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)
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
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)
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 ------------------------------------------------------------
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 <CRTS JHHMMSS.s+DDMMSS> in Simbad. LINEAR = the Lincoln Near-Earth Asteroid Research program, Sesar+ 2013, J/AJ/146/21; <LINEAR NNNNNNNN> 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
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
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