J/AJ/162/253 giz photometry of stars in Cen I field (Martinez-Vazquez+, 2021)
RR Lyrae stars in the newly discovered ultra-faint dwarf galaxy Centaurus I.
Martinez-vazquez C.E., Cerny W., Vivas A.K., Drlica-wagner A., Pace A.B.,
Simon J.D., Munoz R.R., Walker A.R., Allam S., Tucker D.L., Adamow M.,
Carlin J.L., Choi Y., Ferguson P.S., Ji A.P., Kuropatkin N., Li T.S.,
Martinez-delgado D., Mau S., Mutlu-pakdil B., Nidever D.L., Riley A.H.,
Sakowska J.D., Sand D.J., Stringfellow G.S., (the Delve Collaboration)
<Astron. J., 162, 253-253 (2021)>
=2021AJ....162..253M 2021AJ....162..253M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable; Milky Way; Photometry, ugriz
Keywords: Pulsating variable stars; Dwarf galaxies; Time domain astronomy
RR Lyrae variable stars; Local Group; Stellar astronomy
Variable stars
Abstract:
We report the detection of three RR Lyrae (RRL) stars (two RRc and one
RRab) in the ultra-faint dwarf (UFD) galaxy CentaurusI (CenI) and two
Milky Way (MW) δScuti/SX Phoenicis stars based on multi-epoch
giz DECam observations. The two RRc stars are located within two times
the half-light radius (rh) of CenI, while the RRab star (CenI-V3) is
at ∼6rh. The presence of three distant RRL stars clustered this
tightly in space represents a 4.7σ excess relative to the smooth
distribution of RRL in the Galactic halo. Using the newly detected RRL
stars, we obtain a distance modulus to CenI of
µ0=20.354±0.002mag (σ=0.03mag), a heliocentric distance
of D☉=117.7±0.1kpc (σ=1.6kpc), with systematic errors of
0.07mag and 4kpc. The location of the CenI RRL stars in the Bailey
diagram is in agreement with other UFD galaxies (mainly OosterhoffII).
Finally, we study the relative rate of RRc+RRd (RRcd) stars (fcd) in
UFD and classical dwarf galaxies. The full sample of MW dwarf galaxies
gives a mean of fcd=0.28. While several UFD galaxies, such as CenI,
present higher RRcd ratios, if we combine the RRL populations of all
UFD galaxies, the RRcd ratio is similar to the one obtained for the
classical dwarfs (fcd∼0.3). Therefore, there is no evidence for a
different fraction of RRcd stars in UFD and classical dwarf galaxies.
Description:
The data for this work were collected using the Dark Energy Camera
(DECam) on the 4m Blanco Telescope located at the NSF's NOIRLab Cerro
Tololo Inter-American Observatory (CTIO) in Chile. We obtained g, i,
and z time-series photometry. The data were obtained in the second
halves of 2020 February 8-10, 2020 March 4-7, and 2020 March 15-19
(PropID: 2020A-0238, P.I. Martinez-Vazquez).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 79 165 Photometry of the variable stars found in the
field of Cen I
table2.dat 103 5 Coordinates, pulsation properties, and average
photometry of variable stars in Cen I
--------------------------------------------------------------------------------
See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/357 : The Dark Energy Survey (DES): Data Release 1 (Abbott+, 2018)
II/358 : SkyMapper Southern Sky Survey. DR1.1 (Wolf+, 2018)
II/371 : The Dark Energy Survey (DES): Data Release 2 (Abott+, 2021)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/ApJ/781/22 : Region I of La Silla QUEST RR Lyrae star survey (Zinn+, 2014)
J/PASP/126/616 : Variable stars in Leo I dSph (Stetson+, 2014)
J/ApJ/808/11 : RR Lyrae stars in M4. II. Spitzer/IRAC phot. (Neeley+, 2015)
J/MNRAS/462/4349 : Variable stars in Sculptor dSph (Martinez-Vazquez+, 2016)
J/ApJ/850/137 : ISLAndS project. III. Variable stars (Martinez-Vazquez+, 2017)
J/ApJ/855/43 : Distant RR Lyrae stars discovered with HiTS (Medina+, 2018)
J/ApJ/867/105 : ATLAS all-sky stellar ref. cat, ATLAS-REFCAT2 (Tonry+, 2018)
J/AJ/157/35 : Population of pulsating variable stars Sextans (Vivas+, 2019)
J/ApJ/870/83 : Abundances in ultra-faint dwarf gal. GruI & TriII (Ji+, 2019)
J/ApJ/875/77 : Proper motions of MW satellites with Gaia & DES (Pace+, 2019)
J/AJ/161/120 : gri photometry for 73 stars in NGC419 (Martinez-Vazquez+, 2021)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- ID Variable identifier
9- 18 F10.4 d MJDg [56373/58926]? Modified Julian Date of g band
observation of mid-exposure
20- 25 F6.3 mag gmag [19.9/21.6]? Apparent g band magnitude
27- 31 F5.3 mag e_gmag [0.005/0.06]? Uncertainty in gmag
33- 42 F10.4 d MJDi [56357/58926]? Modified Julian Date of i band
observation of mid-exposure
44- 49 F6.3 mag imag [19.8/21.1]? Apparent i band magnitude
51- 55 F5.3 mag e_imag [0.007/0.06]? Uncertainty in imag
57- 66 F10.4 d MJDz [56314/58926]? Modified Julian Date of z band
observation of mid-exposure
68- 73 F6.3 mag zmag [19.8/21.1]? Apparent z band magnitude
75- 79 F5.3 mag e_zmag [0.008/0.07]? Uncertainty in zmag
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- ID Stellar identification
9- 18 F10.6 deg RAdeg [189/190] Degree of right ascension (J2000)
20- 29 F10.6 deg DEdeg [-42/-40] Degree of declination (J2000)
31- 35 F5.2 arcmin Rad [2.38/16.2] Elliptical radius measured from each
star to the center of Cen I
37- 45 F9.7 d Per [0.04/0.74] Period
47- 51 F5.2 mag gmag [20.3/21.3] g-band magnitude
53- 57 F5.2 mag imag [20.1/21] i-band magnitude
59- 63 F5.2 mag zmag [20.1/20.9] z-band magnitude
65 A1 --- l_Ampg [>] Limit flag on Ampg
67- 70 F4.2 mag Ampg [0.27/0.72] Amplitude in g-band
72 A1 --- l_Ampi [>] Limit flag on Ampi
74- 77 F4.2 mag Ampi [0.19/0.37] Amplitude in i-band
79 A1 --- l_Ampz [>] Limit flag in Ampz
81- 84 F4.2 mag Ampz [0.13/0.33] Amplitude in z-band
86-101 A16 --- Type Type of star
103 A1 --- f_Type a = Milky Way field stars (2 occurrences)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 21-Feb-2022