ABSOLUTE PHYSICAL CALIBRATION IN THE INFRARED

We determine an absolute calibration for the Multiband Imaging Photometer for Spitzer 24 μm band and recommend adjustments to the published calibrations for Two Micron All Sky Survey (2MASS), Infrared Array Camera (IRAC), and IRAS photometry to put them on the same scale. We show that consistent results are obtained by basing the calibration on either an average A0V star spectral energy distribution (SED), or by using the absolutely calibrated SED of the Sun in comparison with solar-type stellar photometry (the solar analog method). After the rejection of a small number of stars with anomalous SEDs (or bad measurements), upper limits of ~1.5% root mean square (rms) are placed on the intrinsic infrared (IR) SED variations in both A-dwarf and solar-type stars. These types of stars are therefore suitable as general-purpose standard stars in the IR. We provide absolutely calibrated SEDs for a standard zero magnitude A star and for the Sun to allow extending this work to any other IR photometric system. They allow the recommended calibration to be applied from 1 to 25 μm with an accuracy of ~2%, and with even higher accuracy at specific wavelengths such as 2.2, 10.6, and 24 μm, near which there are direct measurements. However, we confirm earlier indications that Vega does not behave as a typical A0V star between the visible and the IR, making it problematic as the defining star for photometric systems. The integration of measurements of the Sun with those of solar-type stars also provides an accurate estimate of the solar SED from 1 through 30 μm, which we show agrees with theoretical models.

[1]  Daniela Calzetti,et al.  Spectrophotometric Standards from the Far-Ultraviolet to the Near-Infrared: STIS and NICMOS Fluxes , 2001 .

[2]  W. Moore.  Methods of Experimental Physics. , 1960 .

[3]  R. Goody,et al.  Solar Intensity and Limb Darkening between 8. 6 and 13 µ , 1960 .

[4]  Paul S. Smith,et al.  The Multiband Imaging Photometer for Spitzer (MIPS) , 2004 .

[5]  Martin G. Cohen,et al.  Absolute Calibration of the Infrared Array Camera on the Spitzer Space Telescope , 2005, astro-ph/0507139.

[6]  M. Bessell,et al.  JHKLM PHOTOMETRY: STANDARD SYSTEMS, PASSBANDS, AND INTRINSIC COLORS , 1988 .

[7]  Elizabeth A. Lada,et al.  On the Near-Infrared Size of Vega , 2001, astro-ph/0105561.

[8]  S. Price.  Infrared irradiance calibration , 2004 .

[9]  G. Thuillier,et al.  The Solar Spectral Irradiance from 200 to 2400 nm as Measured by the SOLSPEC Spectrometer from the Atlas and Eureca Missions , 2003 .

[10]  Ralph C. Bohlin,et al.  Hubble Space Telescope Absolute Spectrophotometry of Vega from the Far-Ultraviolet to the Infrared , 2004 .

[11]  K. Berrington,et al.  Free-free absorption coefficient of the negative hydrogen ion , 1987 .

[12]  G. C. Strobel.  Stars resembling the Sun , 1996 .

[13]  F. J. Low,et al.  DISCOVERY OF A SHELL AROUND ALPHA-LYRAE , 1984 .

[14]  C. Engelke.  Analytic approximations to the 2-60 microns infrared continua for standard calibration stars - With application to the calibration of spectroscopy and photometry, and the determination of effective temperature and angular size from IR measurements , 1992 .

[15]  Wm. A. Wheaton,et al.  Spectral Irradiance Calibration in the Infrared. XIV. The Absolute Calibration of 2MASS , 2003, astro-ph/0304350.

[16]  S. Price,et al.  Spectral Irradiance Calibration in the Infrared. XV. Absolute Calibration of Standard Stars by Experiments on the Midcourse Space Experiment , 2004 .

[17]  R. Walker.  A discussion on infared astronomy - Near infrared photometry of late-type stars , 1969, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[18]  Michael J. Barlow,et al.  Spectral irradiance calibration in the infrared. I - Ground-based and IRAS broadband calibrations , 1992 .

[19]  C. Beichman,et al.  Infrared astronomical satellite (IRAS) catalogs and atlases. Volume 1: Explanatory supplement , 1988 .

[20]  S. T. Ridgway,et al.  First Results from the CHARA Array. VII. Long-Baseline Interferometric Measurements of Vega Consistent with a Pole-On, Rapidly Rotating Star , 2006, astro-ph/0603327.

[21]  NASA Ames Research Center,et al.  The Mauna Kea Observatories Near-Infrared Filter Set. III. Isophotal Wavelengths and Absolute Calibration , 2005 .

[22]  B. S. Carter.  Southern JHKL standards. , 1990 .

[23]  Hiroyuki Mito,et al.  The IRSA 2MASS all-sky point source catalog , 2008 .

[24]  William Wilson Morgan,et al.  Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas , 1953 .

[25]  R. Kurucz,et al.  A new sunspot umbral model and its variation with the solar cycle , 1986 .

[26]  V. Smith,et al.  Lithium abundances and other clues to envelope burning in small Magellanic Cloud asymptotic giant branch stars , 1993 .

[27]  C. Flynn,et al.  Accurate fundamental parameters for lower main‐sequence stars , 2006, astro-ph/0608504.

[28]  Mark R. Kidger,et al.  High-Precision Near-Infrared Photometry of a Large Sample of Bright Stars Visible from the Northern Hemisphere , 2003 .

[29]  L. Colina,et al.  The 0.12-2.5 micron Absolute Flux Distribution of the Sun for Comparison With Solar Analog Stars , 1996 .

[30]  Gérard Thuillier,et al.  Semiempirical Models of the Solar Atmosphere. I. The Quiet- and Active Sun Photosphere at Moderate Resolution , 2006 .

[31]  A. Cox,et al.  Allen's astrophysical quantities , 2000 .

[32]  A. Goldman,et al.  The 12C/13C and 16O/18O ratios in the solar photosphere , 1987 .

[33]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .

[34]  David E. Trilling,et al.  Decay of Planetary Debris Disks , 2005 .

[35]  D. Padgett,et al.  Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. I. The Stellar Calibrator Sample and the 24 μm Calibration , 2007, 0704.2195.

[36]  G. Rieke,et al.  Absolute calibration of photometry at 1 through 5 microns , 1985 .

[37]  R. Goody,et al.  The Solar Emission Intensity at 11 μ , 1959 .

[38]  Belgium,et al.  ISO-SWS calibration and the accurate modelling of cool-star atmospheres - I. Method , 2000, astro-ph/0008316.

[39]  G. Rieke,et al.  An absolute photometric system at 10 and 20 microns , 1985 .

[40]  A. Triaud,et al.  The Top Ten solar analogs in the ELODIE library , 2004 .

[41]  Johan Holmberg,et al.  The colours of the sun , 2005, astro-ph/0511158.

[42]  E. Avrett,et al.  Structure of the solar chromosphere. II - The underlying photosphere and temperature-minimum region , 1976 .

[43]  Jason T. Wright,et al.  Chromospheric Ca II Emission in Nearby F, G, K, and M Stars , 2004, astro-ph/0402582.

[44]  T. Lee.  INTERSTELLAR EXTINCTION IN THE ORION ASSOCIATION , 1967 .

[45]  H. Holweger,et al.  The photospheric barium spectrum: Solar abundance and collision broadening of Baii lines by hydrogen , 1974 .

[46]  H. Johnson.  Interstellar Extinction in the Galaxy , 1965 .

[47]  M. J. Selby,et al.  Absolute calibration of the infrared flux from Vega at 1.24, 2.20,3.76 and 4.6 μm by comparison with a standard furnace , 1983 .

[48]  G. Rieke,et al.  The interstellar extinction law from 1 to 13 microns. , 1985 .

[49]  M. Bessell.  Standard Photometric Systems , 2005 .

[50]  J. W. Macarthur,et al.  SPECTRAL-ENERGY CURVES OF SUBDWARFS. I. , 1968 .

[51]  M. J. Selby,et al.  Measurement of the absolute monochromatic flux from Vega at λ 2.20 and λ 3.80 μm by comparison with a furnace , 1983 .

[52]  G. Neugebauer,et al.  Stellar flux calibration at 10 and 20 microns using Mariner 6, 7, and 9 results , 1973 .

[53]  K. Y. L. Su,et al.  accepted for publication in ApJ Preprint typeset using L ATEX style emulateapj v. 2/19/04 DEBRIS DISK EVOLUTION AROUND A STARS , 2006 .

[54]  H. Neckel,et al.  Transformation of the absolute solar radiation data into the ‘International Practical Temperature Scale of 1968’ , 1970 .

[55]  R. Humphreys,et al.  M supergiants in the Milky Way and the Magellanic Clouds Colors, spectral types, and luminosities , 1985 .

[56]  Saul J. Adelman,et al.  VEGA : A RAPIDLY ROTATING POLE-ON STAR , 1994 .

[57]  S. T. Ridgway,et al.  Circumstellar material in the Vega inner system revealed by CHARA/FLUOR , 2006 .

[58]  M. Kessler,et al.  Infrared standards for ISO - I. A new calibration of mid infrared photometry , 1998 .

[59]  C. Keller,et al.  Solar Carbon Monoxide, Thermal Profiling, and the Abundances of C, O, and Their Isotopes , 2006, astro-ph/0606153.

[60]  J. Carpenter.  Color Transformations for the 2MASS Second Incremental Data Release , 2001, astro-ph/0101463.