J/ApJ/916/10 LBT photometry in Pisces II and Pegasus III (Garofalo+, 2021)
Born in a pair (?): Pisces II and Pegasus III.
Garofalo A., Tantalo M., Cusano F., Clementini G., Calura F., Muraveva T.,
Paris D., Speziali R.
<Astrophys. J., 916, 10 (2021)>
=2021ApJ...916...10G 2021ApJ...916...10G
ADC_Keywords: Photometry, UBV; Stars, variable
Keywords: Dwarf galaxies ; Galaxy distances ; Variable stars
Abstract:
We have used B, V time-series photometry collected with the Large
Binocular Telescope to undertake the first study of variable stars in
the Milky Way ultra-faint dwarf (UFD) satellites Pisces II and
PegasusIII. In Pisces II we have identified an RRab star, one
confirmed and a candidate SX Phoenicis star, and a variable with
uncertain classification. In Pegasus III we confirmed the variability
of two sources: an RRab star and a variable with uncertain
classification, similar to the case found in Pisces II. Using the
intensity-averaged apparent magnitude of the bona fide RRab star in
each galaxy, we estimate distance moduli of (m-M)0=21.22±0.14mag
(d=175±11kpc) and 21.21±0.23mag (d=174±18kpc) for Pisces II and
Pegasus III, respectively. Tests performed to disentangle the actual
nature of variables with an uncertain classification led us to
conclude that they most likely are bright, long-period, and very
metal-poor RRab members of their respective hosts. This may indicate
that Pisces II and Pegasus III contain a dominant old stellar
population (t>12Gyr) with metallicity <[Fe/H]>-1.8dex along with,
possibly, a minor, more metal-poor component, as supported by the V,
B-V color-magnitude diagrams of the two UFDs and their
spectroscopically confirmed members. The metallicity spread that we
derived from our data sample is ≳0.4dex in both systems. Lastly, we
built isodensity contour maps that do not reveal any irregular shape,
thus making the existence of a physical connection between these UFDs
unlikely.
Description:
B, V time-series photometry of Pisces II (Psc II) was collected with
the Large Binocular Cameras (LBCs) of the LBT program
(PI: G. Clementini), which targeted also the Milky Way ultra-faint
dwarf (UFD) Pegasus III. The data consist of 26 B and 26 V images for
Psc II and 28 B and 28 V images for Peg III, each with an exposure
time of 180s, acquired over six nights from 2015 October to December.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
22 58 31.00 +05 57 09.0 Pisces II = Psc II
22 24 22.60 +05 25 11.9 Pegasus III = NAME Peg III
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 60 159 B and V timeseries photometry of the Psc II and
Peg III variable stars
table5.dat 103 8 Properties of the variable stars identified in
Psc II and Peg III
--------------------------------------------------------------------------------
See also:
II/350 : VLT Survey Telescope ATLAS (Shanks+, 2015)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/A+A/312/111 : [Fe/H] from RR Lyrae light curves (Jurcsik+, 1996)
J/A+A/391/945 : HST phot. of 74 galactic globular clusters (Piotto+, 2002)
J/A+A/421/937 : Metal abundances of LMC RR Lyrae (Gratton+, 2004)
J/AJ/129/267 : RR Lyrae variables in NGC 5272 (Cacciari+, 2005)
J/MNRAS/371/1503 : Synthetic photometry of RR Lyr (Marconi+, 2006)
J/ApJ/674/L81 : Variable stars in dwarf galaxy CVn I (Kuehn+, 2008)
J/AcA/58/293 : Type-II and anomalous Cepheids in LMC (Soszynski+, 2008)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/ApJ/710/1664 : BV photometry in Leo IV and Leo V dSphs (de Jong+, 2010)
J/ApJ/723/1632 : Abundance spreads in Bootes I and Segue 1 (Norris+, 2010)
J/ApJ/733/46 : Velocity measurements in Segue 1 (Simon+, 2011)
J/ApJ/756/108 : HST VI phot. of variable stars in Leo T (Clementini+, 2012)
J/ApJ/752/42 : BV time series in Ursa Major II (Dall'Ora+, 2012)
J/ApJ/756/121 : Variable stars in Her dwarf galaxy (Musella+, 2012)
J/ApJ/756/79 : Optical phot. in 3 Local Group dwarf galaxies (Sand+, 2012)
J/ApJ/767/62 : RR Lyrae stars BV photometry in UMa I (Garofalo+, 2013)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/ApJS/213/9 : Catalina Surveys periodic variable stars (Drake+, 2014)
J/MNRAS/437/2307 : LMC anomalous Cepheid Ks light curves (Ripepi+, 2014)
J/ApJ/793/135 : Positions and distances of RR Lyrae stars (Sesar+, 2014)
J/MNRAS/479/5343 : Nearby dwarf galaxy in Magellanic bridge (Koposov+, 2018)
J/ApJ/857/145 : MagLiteS Carina II and Carina III spectroscopy (Li+, 2018)
J/ApJ/855/43 : Distant RR Lyrae stars discovered with HiTS (Medina+, 2018)
J/MNRAS/481/1195 : GaiaDR2 RR Lyrae stars as standard candles (Muraveva+, 2018)
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Gal UFD galaxy identifier
9- 10 A2 --- Var Variable star identifier
12- 20 F9.5 d HJDB [297.7/358.7] B band observation heliocentric
Julian Date; HJDB-2457000
22- 28 F7.4 mag Bmag [21.44/24.95] Apparent Johnson B band magnitude
30- 35 F6.4 mag e_Bmag [0.01/0.3] Uncertainty in Bmag
37- 45 F9.5 d HJDV [297.7/358.7]? V band observation heliocentric
Julian Date; HJDV-2457000
47- 53 F7.4 mag Vmag [21.18/24.44]? Apparent Johnson V band magnitude
55- 60 F6.4 mag e_Vmag [0.01/0.2]? Uncertainty in Vmag
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Gal UFD galaxy identifier
9- 10 A2 --- Var Variable star identifier
11- 14 A4 --- n_Var See Section 7 for the cases of V4 in PscII and
V2 in PegIII
16- 17 I2 h RAh Hour of right ascension (J2000)
19- 20 I2 min RAm Minute of right ascension (J2000)
22- 27 F6.3 s RAs Second of right ascension (J2000)
29 A1 --- DE- Sign of declination (J2000)
30 I1 deg DEd Degree of declination (J2000)
32- 33 I2 arcmin DEm Arcminute of declination (J2000)
35- 39 F5.2 arcsec DEs Arcsecond of declination (J2000)
41- 49 A9 --- OType Object type
51- 57 F7.5 d Per [0.049/0.73] Period
59- 66 F8.4 d HJD [296.71/357.56]? Heliocentric Julian Date,
HJD-2457000
68- 73 F6.3 mag Bmag [21.98/24.245]? Mean B-band Johnson magnitude
75- 79 F5.3 mag Ab [0.94/1.26]? Extinction in B-band
81- 86 F6.3 mag Vmag [21.63/23.935]? Mean V-band Johnson magnitude
88- 92 F5.3 mag Av [0.69/1.16]? Extinction in V-band
94-103 A10 [Sun] [Fe/H] Metallicity
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Dec-2022