J/ApJ/743/76 Spitzer photometry of LMC Cepheids (Scowcroft+, 2011)
The Carnegie Hubble Program: the Leavitt law at 3.6 µm and 4.5 µm in the
Large Magellanic Cloud.
Scowcroft V., Freedman W.L., Madore B.F., Monson A.J., Persson S.E.,
Seibert M., Rigby J.R., Sturch L.
<Astrophys. J., 743, 76 (2011)>
=2011ApJ...743...76S 2011ApJ...743...76S
ADC_Keywords: Magellanic Clouds ; Stars, variable ; Photometry, infrared
Keywords: infrared: stars - Magellanic Clouds - stars: distances -
stars: variables: Cepheids
Abstract:
The Carnegie Hubble Program is designed to improve the extragalactic
distance scale using data from the post-cryogenic era of Spitzer. The
ultimate goal is a determination of the Hubble constant to an accuracy
of 2%. This paper is the first in a series on the Cepheid population
of the Large Magellanic Cloud, and focusses on the period-luminosity
(PL) relations (Leavitt laws) that will be used, in conjunction with
observations of Milky Way Cepheids, to set the slope and zero point of
the Cepheid distance scale in the mid-infrared. To this end, we have
obtained uniformly sampled light curves for 85 LMC Cepheids, having
periods between 6 and 140 days. PL and period-color relations are
presented in the 3.6um and 4.5um bands. We demonstrate that the 3.6um
band is a superb distance indicator. The cyclical variation of the
[3.6]-[4.5] color has been measured for the first time. We attribute
the amplitude and phase of the color curves to the dissociation and
recombination of CO molecules in the Cepheid's atmosphere. The CO
affects only the 4.5um flux making it a potential metallicity
indicator.
Description:
The data were obtained in programs 61000, 61004, 61005, 61006, and
61007, executed between 2009 October 3 and 2010 July 18, at the start
of the "Warm Spitzer" mission. Each Cepheid was observed at 24
epochs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 54 85 Magnitudes for LMC Cepheids
table2.dat 43 2040 Photometry of sources
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See also:
J/ApJ/730/119 : HST observations of Cepheids in SN Ia hosts (Riess+, 2011)
J/MNRAS/397/933 : LMC type II Cepheids JHKs magnitudes (Matsunaga+, 2009)
J/AcA/58/163 : VI light curves of LMC classical Cepheids (Soszynski+, 2008)
J/ApJ/679/71 : Mid-IR period-luminosity relations (Freedman+, 2008)
J/A+A/415/521 : BVRIJK and velocities for MC Cepheids (Storm+, 2004)
J/AJ/128/2239 : JHKs photometry of 92 LMC Cepheids (Persson+, 2004)
J/ApJS/142/71 : BVRI observations of LMC Cepheids (Sebo+, 2002)
J/AcA/49/223 : BVI photometry of OGLE LMC Cepheids (Udalski+, 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Cepheid name (HVNNNNN or P71_U01)
9- 15 F7.3 d Period Final adopted period
17- 22 F6.3 mag [3.6] Spitzer/IRAC 3.6 micron band magnitude (1)
24- 28 F5.3 mag e_[3.6] The 1σ error in [3.6] (2)
30- 35 F6.3 mag [4.5] Spitzer/IRAC 4.5 micron band magnitude (1)
37- 41 F5.3 mag e_[4.5] The 1σ error in [4.5] (2)
43- 48 F6.3 mag Color The (3.6-4.5) band color index (1)
50- 54 F5.3 mag e_Color The 1σ error in Color (2)
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Note (1): Time-averaged (intensity-mean) magnitude.
Note (2): For Cepheids with Period ≤ 12 days the uncertainties scale with
1/N0.5 rather than 1/N as the observations of short period
Cepheids were not phase locked.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Cepheid name
9- 17 F9.3 d MJD Modified Julian Date; JD-2400000.5
19- 24 F6.3 mag [3.6] Spitzer/IRAC 3.6 micron band magnitude (1)
26- 30 F5.3 mag e_[3.6] The 1σ error in [3.6]
32- 37 F6.3 mag [4.5] Spitzer/IRAC 4.5 micron band magnitude (1)
39- 43 F5.3 mag e_[4.5] The 1σ error in [4.5]
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Note (1): Each magnitude point corresponds to a flux weighted average of the
five dither positions.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 02-May-2013