J/ApJ/816/49 Spitzer/IRAC observations of SMC Cepheids (Scowcroft+, 2016)
The Carnegie Hubble Program: the distance and structure of the SMC as revealed
by mid-infrared observations of cepheids.
Scowcroft V., Freedman W.L., Madore B.F., Monson A., Persson S.E., Rich J.,
Seibert M., Rigby J.R.
<Astrophys. J., 816, 49 (2016)>
=2016ApJ...816...49S 2016ApJ...816...49S (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, variable ; Photometry, infrared
Keywords: galaxies: individual: SMC; stars: variables: Cepheids
Abstract:
Using Spitzer observations of classical Cepheids we have measured the
true average distance modulus of the Small Magellanic Cloud (SMC) to
be 18.96±0.01stat±0.03sysmag (corresponding to 62±0.3kpc),
which is 0.48±0.01mag more distant than the LMC. This is in
agreement with previous results from Cepheid observations, as well as
with measurements from other indicators such as RR Lyrae stars and the
tip of the red giant branch. Utilizing the properties of the
mid-infrared Leavitt Law we measured precise distances to individual
Cepheids in the SMC, and have confirmed that the galaxy is tilted and
elongated such that its eastern side is up to 20kpc closer than its
western side. This is in agreement with the results from red clump
stars and dynamical simulations of the Magellanic Clouds and Stream.
Description:
For the present survey we selected 92 Harvard variable Cepheids spread
over the SMC. These objects have all been extensively studied over the
years; archival optical and/or near-IR data is available for all of
them and the vast majority were measured by OGLE (Udalski et al.
1992AcA....42..253U 1992AcA....42..253U, 1997AcA....47..319U 1997AcA....47..319U; Soszynski et al. 2010,
J/AcA/60/17).
Ninety fundamental mode SMC type I (and two type II) Cepheids were
observed with Spitzer between 2010 August and 2012 January (Program ID
70010, P.I. Madore). Each light curve has 12 epochs, each spaced by
approximately P/12 days, where P is the Cepheid's pulsation period.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 58 2178 Individual photometric data points for
the SMC classical Cepheids
table2.dat 40 90 Mean-light magnitudes for SMC Cepheids
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See also:
J/ApJ/780/59 : The Araucaria project: EBs in SMC (Graczyk+, 2014)
J/MNRAS/420/585 : AKARI observations of SMC Cepheids (Ngeow+, 2012)
J/ApJ/759/146 : Spitzer/IRAC photom. for 37 Galactic Cepheids (Monson+, 2012)
J/ApJ/743/76 : Spitzer photometry of LMC Cepheids (Scowcroft+, 2011)
J/AcA/60/165 : VI light curves of SMC RR Lyrae (Soszynski+, 2010)
J/ApJ/715/277 : Insights into the Cepheid distance scale (Bono+, 2010)
J/AcA/60/17 : VI light curves of SMC classical Cepheids (Soszynski+, 2010)
J/A+A/476/73 : Cepheid Period/Luminosity relation (Fouque+, 2007)
J/ApJ/658/345 : CRIc photometry of Magellanic Bridge Fields (Harris, 2007)
J/AJ/128/2239 : JHKs photometry of 92 LMC Cepheids (Persson+, 2004)
J/A+A/415/521 : BVRIJK and velocities for MC Cepheids (Storm+, 2004)
J/A+A/385/793 : Cepheids in Magellanic Clouds. II. (Antonello+, 2002)
J/PASP/111/812 : VRI Phot of Cepheids in the Magellanic Clouds (Barnes+ 1999)
J/AcA/49/543 : OGLE LMC + SMC Cepheids VI photometry (Pietrzynski+, 1999)
J/ApJS/117/135 : Photometry of Cepheids in Magellanic Clouds (Moffett+ 1998)
J/AcA/48/147 : OGLE SMC BVI photometry (Udalski+ 1998)
J/AJ/108/932 : Variable stars in the SMC cluster NGC 330 (Sebo+, 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- ID Cepheid identifier
9- 20 F12.6 d MHJD [55434.8/55927.9] Modified Heliocentic Julian
Date; JD-2400000.5
22- 30 F9.6 mag 3.6mag [9.1/14]? Spitzer/IRAC 3.6um band magnitude
32- 39 F8.6 mag e_3.6mag [0.002/0.9]? The 1σ uncertainty in 3.6mag
41- 49 F9.6 mag 4.5mag [9.1/14]? Spitzer/IRAC 4.5um band magnitude
51- 58 F8.6 mag e_4.5mag [0.001/1]? The 1σ uncertainty in 4.5mag
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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 --- ID Cepheid identifier
9- 14 F6.4 d logP [0.8/2.4] Log of pulsation period
16- 21 F6.3 mag 3.6mag [9.4/13.9] Spitzer/IRAC 3.6um magnitude;
in Vega system
23- 27 F5.3 mag e_3.6mag [0.004/0.04] 3.6mag uncertainty (1)
29- 34 F6.3 mag 4.5mag [9.3/13.9] Spitzer/IRAC 4.5um magnitude;
in Vega system
36- 40 F5.3 mag e_4.5mag [0.003/0.04] 4.5mag uncertainty (1)
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Note (1): For Cepheids with P≤12 days the uncertainties scale with 1/(N0.5)
rather than 1/N, as the observations of short period Cepheids were not
phase locked. See the appendix of Scowcroft+, 2011, J/ApJ/743/76
for details.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Mar-2016