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J/ApJ/849/150      RR Lyrae candidates in the MW outer halo      (Cohen+, 2017)

The outer halo of the Milky Way as probed by RR Lyr variables from the Palomar Transient Facility. Cohen J.G., Sesar B., Bahnolzer S., He K., Kulkarni S.R., Prince T.A., Bellm E., Laher R.R. <Astrophys. J., 849, 150 (2017)> =2017ApJ...849..150C
ADC_Keywords: Stars, variable; Photometry, SDSS; Radial velocities; Stars, distances Keywords: Galaxy: halo ; Galaxy: kinematics and dynamics ; stars: variables: RR Lyrae Abstract: RR Lyrae stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way (MW). This is because they are easy to find in the light-curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112 RR Lyr stars beyond 50kpc in the outer halo of the MW, excluding the Sgr streams, for which we have obtained moderate-resolution spectra with Deimos on the Keck II Telescope. Four of these have distances exceeding 100kpc. These were selected from a much larger set of 447 candidate RR Lyr stars that were data-mined using machine-learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112 RR Lyr stars we determine the radial velocity dispersion in the outer halo of the MW to be ∼90km/s at 50kpc, falling to about 65km/s near 100 kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447 candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as r-4. Description: The Palomar Transient Facility (PTF) is a wide-area, two-band (g and R filters), deep (R∼20.6 single epoch, ∼23mag co-added) survey aimed at systematic exploration of the optical transient sky. The PTF ran for 3yr, ending 2012 December 31, and then transitioned to the intermediate-PTF (iPTF). The project uses the CFH12k mosaic camera mounted on the Palomar Observatory 48-inch Samuel Oschin Schmidt Telescope. By the end of 2014 September, ∼12000deg2 of sky had been observed by the iPTF in the Mould R filter (similar in shape to the SDSS r-band filter, but shifted 27Å redward) and ∼2300deg2 in the SDSS g' filter at least 30 times each. A spectroscopic campaign to obtain radial velocities for RR Lyr candidates began at the Keck Observatory with the Deimos spectrograph in the spring of 2014 following a brief effort to use the Double Spectrograph (DBSP) on the Hale Telescope at the Palomar Observatory, which yielded one useful spectrum. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . this file table1.dat 63 116 Light curve parameters for RR Lyr candidates table2.dat 54 116 Radial velocities for RR Lyr candidates
See also: I/315 : UCAC3 Catalogue (Zacharias+ 2009) J/MNRAS/375/1381 : Kinematics of RR Lyr and HB stars in NGP (Kinman+, 2007) J/ApJ/678/851 : RR Lyrae survey in the Galactic Halo (Keller+, 2008) J/ApJ/678/865 : LONEOS-I RR Lyrae stars (Miceli+, 2008) J/ApJ/684/1143 : BHB candidates in the Milky Way (Xue+, 2008) J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009) J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009) J/AJ/139/59 : Milky Way halo velocity dispersion profile (Brown+, 2010) J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010) J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010) J/AJ/142/187 : HST obs. of 7 Pop.II variable stars (Benedict+, 2011) J/ApJ/740/65 : VLA search for 5GHz radio transients (Ofek+, 2011) J/ApJ/731/4 : Galactic halo as seen by the CFHTLS (Sesar+, 2011) J/ApJ/738/79 : SDSS-DR8 BHB stars in the Milky Way's halo (Xue+, 2011) J/AJ/144/114 : Radial velocities of 6 field RR Lyrae (Sesar+, 2012) J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012) J/ApJ/756/23 : V-band follow-up of RR Lyrae from SEKBO (Akhter+, 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/AJ/146/21 : LINEAR. II. Catalog of RR Lyrae stars (Sesar+, 2013) J/ApJS/213/9 : Catalina Surveys periodic variable stars (Drake+, 2014) J/ApJ/793/135 : Positions and distances of RR Lyrae stars (Sesar+, 2014) J/ApJ/784/170 : SEGUE K giant survey. II. Dist. of 6036 stars (Xue+, 2014) J/ApJ/788/105 : XSTPS RR Lyrae in the north Galactic cap (Faccioli+, 2014) J/A+A/584/A44 : Photom. classification of QSO from RCS-2 (Carrasco+, 2015) J/MNRAS/446/2251 : Southern Catalina Survey type-ab RR Lyrae (Torrealba+, 2015) J/ApJ/817/73 : QSOs & RR Lyrae in PS1 3π Data (Hernitschek+ 2016) J/ApJ/838/107 : Distances to RRab stars from WISE and Gaia (Sesar+, 2017) 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) http://www.ptf.caltech.edu/news/DR3 : The Palomar Transient Facility DR3 http://www.sdss3.org/ : The SDSS-III home page Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1 A1 --- Sgr Sgr, a=Probable Sgr Stream 3- 12 F10.6 deg RAdeg Right ascension, decimal degrees (J2000) 14- 22 F9.6 deg DEdeg Declination, decimal degrees (J2000) 24- 32 F9.7 d Per [0.4/0.9] Period 34- 41 F8.2 d HJD [55007.9/57538.7] Epoch of maximum light in heliocentric Julian date; HJD-2400000 (1) 43- 46 F4.2 mag AmpR [0.4/1.2] Amplitude of variation in PTF-R band 48- 52 F5.2 mag Rmag [0/20.7]? Mean PTF-R band AB magnitude 54- 56 I3 --- N(R) [0/723]? Number of PTF-R band epochs star detected in late 2016 58- 60 I3 --- N(g) [0/385]? Number of PTF-g band epochs star detected in late 2016 63 I1 --- Qual [0/3]? Quality (2)
Note (1): Epoch of maximum light in heliocentric Julian date - 2400000 days. This choice, made for ease of computations, requires 7 digits in the period for accurate phasing at the present epoch Note (2): Observed R light curve resembles that of a RR Lyr; code as follows: 1 = excellent; 2 = probable; 3 = uncertain.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1 A1 --- Sgr Sgr, a=Probable Sgr Stream 3- 12 F10.6 deg RAdeg Right ascension, decimal degrees (J2000) 14- 22 F9.6 deg DEdeg Declination, decimal degrees (J2000) 24- 28 F5.1 kpc Dist [50/109.1] Heliocentric distance 30 I1 --- Nsp [1/2] Number of spectra 32- 37 F6.1 km/s RV-GSR [-256.2/224] Radial velocity, Galactic system of rest (3) 39- 42 F4.1 km/s e_RV-GSR [12/29] Uncertainty in RVel 44- 51 A8 --- Date Approximate RV date of observation MM/YYYY or MM/DD/YYYY; "dup" = 2 spectra taken 54 A1 --- f_Nsp Flag on spectra taken (4)
Note (3): RV-GSR is corrected to the systemic velocity, then to the heliocentric velocity, and then to the Galactic system of rest. Note (4): Flag on spectra taken -- d = A DBSP spectrum taken with the Hale Telescope at Palomar Observatory.
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Jun-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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