J/ApJ/794/107 Distance to NGC6822 with Spitzer/FourStar Photometry (Rich+, 2014)
A new Cepheid distance measurement and method for NGC 6822.
Rich J.A., Persson S.E., Freedman W.L., Madore B.F., Monson A.J.,
Scowcroft V., Seibert M.
<Astrophys. J., 794, 107 (2014)>
=2014ApJ...794..107R 2014ApJ...794..107R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Photometry, infrared
Keywords: galaxies: distances and redshifts -
galaxies: individual: NGC 6822 - infrared: galaxies -
infrared: stars - stars: variables: Cepheids
Abstract:
We present a revised distance to the nearby galaxy NGC 6822 using a
new multi-band fit to both previously published and new optical,
near-, and mid-infrared data for Cepheid variables. The new data
presented in this study include multi-epoch observations obtained in
3.6 µm and 4.5 µm with the Spitzer Space Telescope taken for the
Carnegie Hubble Program. We also present new observations in J, H, and
Ks with FourStar on the Magellan Baade Telescope at Las Campanas
Observatory. We determine mean magnitudes and present new
period-luminosity relations in V, I, J, H, Ks, Infrared Array Camera
3.6 µm, and 4.5 µm. In addition to using the multi-band distance
moduli to calculate extinction and a true distance, we present a new
method for determining an extinction-corrected distance modulus from
multi-band data with varying sample sizes. We combine the distance
moduli and extinction for individual stars to determine
E(B-V)=0.35±0.04 and a true distance modulus
µo=23.38±0.02stat±0.04sys.
Description:
In this paper, we use both previously published as well as new
observations. To compose our sample of Cepheids, we refer to the work
of Pietrzynski et al. (2004, J/AJ/128/2815), which includes
coordinates and the most up to date list of Cepheids in NGC 6822,
including the re-discovery of Cepheids previously observed with both
photographic plates and CCDs (Hubble, 1925ApJ....62..409H 1925ApJ....62..409H; Kayser,
1967AJ.....72..134K 1967AJ.....72..134K; McAlary et al. 1983ApJ...273..539M 1983ApJ...273..539M; Gallart et al.
1996AJ....112.1928G 1996AJ....112.1928G; Antonello et al. 2002A&A...386..860A 2002A&A...386..860A). To
simplify matters, we refer to the stars used in our analysis by the
unique identifier given in Pietrzynski et al. (2004, J/AJ/128/2815)
and adopt the periods determined with their well-sampled data. We
restrict our analysis to Cepheids with periods greater than six days,
resulting in 39 stars.
Objects:
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RA (ICRS) DE Designation(s)
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19 44 56.20 -14 47 51.3 NGC 6822 = NAME Barnard's Galaxy
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
sample.dat 40 27 List of studied stars
table1.dat 33 575 New Spitzer & FourStar Photometry
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See also:
J/AJ/128/2815 : ARAUCARIA project: NGC 6822 Cepheid variables
(Pietrzynski+, 2004)
J/A+A/431/1189 : BV photometry of NGC 6822 variables (Baldacci+, 2005)
J/MNRAS/421/2998 : NGC 6822 Cepheids JHKs light curves (Feast+, 2012)
J/A+A/572/A26 : HST photometry in NGC 6822 (Fusco+, 2014)
Byte-by-byte Description of file: sample.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Cepheid identifier
([PGU2004] cepNNN in Simbad)
9- 10 I2 h RAh Right ascension (J2000)
12- 13 I2 min RAm Right ascension (J2000)
15- 19 F5.2 s RAs Right ascension (J2000)
21 A1 --- DE- Declination sign (J2000)
22- 23 I2 deg DEd Declination (J2000)
25- 26 I2 arcmin DEm Declination (J2000)
28- 31 F4.1 arcsec DEs Declination (J2000)
33- 40 F8.4 d Per Period (from table 2 of the paper)
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Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Cepheid identifier
([PGU2004] cepNNN in Simbad)
8- 12 A5 --- Band Spitzer/IRAC, FourStar pass band
14- 19 F6.3 mag mag Observed magnitude in Band
21- 25 F5.3 mag e_mag The 1σ uncertainty in mag
27- 33 F7.1 d MJD Modified Julian Date of observation
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 15-May-2017