J/ApJ/759/146 Spitzer/IRAC photometry for 37 Galactic Cepheids (Monson+, 2012)
The Carnegie Hubble Program: the Leavitt law at 3.6 and 4.5 µm in the
Milky Way.
Monson A.J., Freedman W.L., Madore B.F., Persson S.E., Scowcroft V.,
Seibert M., Rigby J.R.
<Astrophys. J., 759, 146 (2012)>
=2012ApJ...759..146M 2012ApJ...759..146M
ADC_Keywords: Photometry, infrared ; Stars, variable ; Stars, distances ;
Reddening
Keywords: infrared: stars; stars: variables: Cepheids
Abstract:
The Carnegie Hubble Program (CHP) is designed to calibrate the
extragalactic distance scale using data from the post-cryogenic era of
the Spitzer Space Telescope. The ultimate goal of the CHP is a
systematic improvement in the distance scale leading to a
determination of the Hubble constant to within an accuracy of 2%. This
paper focuses on the measurement and calibration of the Galactic
Cepheid period-luminosity (PL, Leavitt) relation using the warm
Spitzer/IRAC 1 and 2 bands at 3.6 and 4.5µm. We present photometric
measurements covering the period range 4-70 days for 37 Galactic
Cepheids. Data at 24 phase points were collected for each star. Three
PL relations of the form M=a(log(P)-1)+b are derived. The method
adopted here takes the slope a to be -3.31, as determined from the
Spitzer Large Magellanic Cloud (LMC) data of Scowcroft et al.
(Cat. J/ApJ/743/76). Using the geometric Hubble Space Telescope
guide-star distances to 10 Galactic Cepheids, we find a calibrated
3.6µm PL zero point of -5.80±0.03. Together with our value for
the LMC zero point, we determine a reddening-corrected distance
modulus of 18.48±0.04mag to the LMC. The mid-IR period-color diagram
and the [3.6]-[4.5] color variation with phase are interpreted in
terms of CO absorption at 4.5µm. This situation compromises the use
of the 4.5µm data for distance determinations.
Description:
Observations were made using the Spitzer Space Telescope as part of a
two-year Exploration Science Program, PID 60010: The Hubble Constant
(Freedman et al. 2008sptz.prop60010F). The warm Spitzer mission
started in 2009 (Cycle-6) and the Galactic Cepheid observations were
completed in early 2011.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 37 Selected Galactic Cepheids and adopted parallaxes
table3.dat 47 887 Spitzer IRAC photometry for Galactic Cepheids
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
J/A+A/550/A70 : Galactic & Magellanic Cloud Cepheids dist. (Groenewegen 2013)
J/ApJ/748/107 : A global model for MC and Galactic Cepheids (Pejcha+, 2012)
J/ApJ/747/50 : Dist. to Cepheids using the Wesenheit function (Ngeow, 2012)
J/MNRAS/419/1637 : Nearby red clump stars JHK observations (Laney+, 2012)
J/ApJS/193/12 : JHK photometry of Northern Galactic Cepheids (Monson+, 2011)
J/ApJ/743/76 : Spitzer photometry of LMC Cepheids (Scowcroft+, 2011)
J/A+A/534/A94 : Milky Way Cepheids radial velocities (Storm+, 2011)
J/AJ/139/519 : Carnegie supernova project. SNe Ia (Contreras+, 2010)
J/MNRAS/389/1336 : Reddenings of FGK supergiants + Cepheids (Kovtyukh+, 2008)
J/A+A/476/73 : Cepheid Period/Luminosity relation calibration (Fouque+, 2007)
J/A+A/404/423 : BVI photometry of Galactic Cepheids (Tammann+, 2003)
J/A+AS/143/211 : Galactic Cepheids BVRI photometry (Berdnikov+, 2000)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Cepheid identifier
13- 17 F5.3 [d] logP [0.5/1.9] log of Period (1)
19- 20 I2 h RAh Hour of right ascension (J2000) (1)
22- 23 I2 min RAm Minute of right ascension (J2000)
25- 28 F4.1 s RAs Second of right ascension (J2000)
30 A1 --- DE- Sign of declination (J2000) (1)
31- 32 I2 deg DEd Degree of declination (J2000) (1)
34- 35 I2 arcmin DEm Arcminute of declination (J2000)
37- 38 I2 arcsec DEs Arcsecond of declination (J2000)
40- 44 F5.3 mag E(B-V) [0.01/1.3] Weighted B-V reddening (2)
46- 50 F5.3 mag e_E(B-V) [0.007/0.2] E(B-V) uncertainty (2)
52- 55 F4.2 mas Plx1 [1.9/3.7]? HST parallax (3)
57- 60 F4.2 mas e_Plx1 [0.1/0.3]? HST parallax uncertainty (3)
62- 65 F4.2 mas Plx2 [0.2/3.7]? MS parallax (4)
67- 70 F4.2 mas e_Plx2 [0.01/0.2]? MS parallax uncertainty (4)
72 A1 --- r_Plx2 [f-j] Reference for Plx2 (5)
74- 77 F4.2 mas Plx3 [0.2/4.7]? IRSB parallax (6)
79- 82 F4.2 mas e_Plx3 [0.01/0.4]? IRSB parallax uncertainty (6)
84 A1 --- r_Plx3 [k] Reference for Plx3 (5)
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Note (1): Values adopted from the General Catalog of Variable Stars
(Samus et al. 2009, Cat. B/gcvs).
The periods for V340 Nor and U Car were recomputed; see the text.
Note (2): Weighted reddening from (see table 2 of paper):
* average photometric reddenings (Fouque et al. 2007, J/A+A/476/73)
* spectroscopic reddenings (Kovtyukh et al. 2008, J/MNRAS/389/1336)
* space reddenings (Turner 2010Ap&SS.326..219T 2010Ap&SS.326..219T;
Benedict et al. 2007AJ....133.1810B 2007AJ....133.1810B).
Note (3): Hubble Space Telescope parallaxes adopted from Benedict et al.
(2007AJ....133.1810B 2007AJ....133.1810B). The Lutz-Kelker bias correction is applied in
the PL analysis; see Table 5.
Note (4): Main Sequence fitting to candidate cluster.
Cluster parallaxes adopted from Turner (2010Ap&SS.326..219T 2010Ap&SS.326..219T),
unless flagged otherwise.
Note (5): Reference flag as follows:
f = Turner (2011RMxAA..47..127T 2011RMxAA..47..127T).
g = Majaess et al. (2011ApJ...741L..27M 2011ApJ...741L..27M).
h = Majaess et al. (2012ApJ...748L...9M 2012ApJ...748L...9M).
i = Majaess et al. (2012ApJ...747..145M 2012ApJ...747..145M).
j = Turner & Burke (2002AJ....124.2931T 2002AJ....124.2931T).
k = Matthews et al. (1995AJ....110.2280M 1995AJ....110.2280M).
Note (6): Infrared Surface Brightness parallaxes; adopted from Storm et al.
(2011, J/A+A/534/A94), unless flagged otherwise.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Cepheid identifier
14- 23 F10.4 d MJD [55129/55551] Heliocentric MJD (1)
25- 29 F5.3 mag [3.6] [0.7/8] Spitzer/IRAC 3.6 micron band magnitude
31- 35 F5.3 mag e_[3.6] [0.002/0.03] Uncertainty in [3.6]
37- 41 F5.3 mag [4.5] [0.9/8] Spitzer/IRAC 4.5 micron band magnitude
43- 47 F5.3 mag e_[4.5] [0.001/0.03] Uncertainty in [4.5]
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Note (1): Determined from averaging the 18 "HMJD" header keywords at each
epoch (9 exposures in each channel) [HMJD=HJD-2400000.5]
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 16-Jul-2014