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MIPSGAL: A Survey of the Inner Galactic Plane at 24 and 70 μm
MIPSGAL is a 278 deg2 survey of the inner Galactic planeusing the Multiband Infrared Photometer for Spitzer aboard the SpitzerSpace Telescope. The survey field was imaged in two passbands, 24 and 70μm with resolutions of 6″ and 18″, respectively. Thesurvey was designed to provide a uniform, well-calibrated andwell-characterized data set for general inquiry of the inner Galacticplane and as a longer-wavelength complement to the shorter-wavelengthSpitzer survey of the Galactic plane: Galactic Plane Infrared MappingSurvey Extraordinaire. The primary science drivers of the current surveyare to identify all high-mass (M>5 Mȯ) protostars inthe inner Galactic disk and to probe the distribution, energetics, andproperties of interstellar dust in the Galactic disk. The observationswere planned to minimize data artifacts due to image latents at 24 μmand to provide full coverage at 70 μm. Observations at eclipticlatitudes within 15° of the ecliptic plane were taken at multipleepochs to help reject asteroids. The data for the survey were collectedin three epochs, 2005 September-October, 2006 April, and 2006 Octoberwith all of the data available to the public. The estimated point-sourcesensitivities of the survey are 2 and 75 mJy (3 σ) at 24 and 70μm, respectively. Additional data processing was needed to mitigateimage artifacts due to bright sources at 24 μm and detectorresponsivity variations at 70 μm due to the large dynamic range ofthe Galactic plane. Enhanced data products including artifact-mitigatedmosaics and point-source catalogs are being produced with the 24 μmmosaics already publicly available from the NASA/IPAC Infrared ScienceArchive. Some preliminary results using the enhanced data products aredescribed.
| Near-Infrared and Mid-Infrared Spectroscopy with the Infrared Camera (IRC) for AKARI
The Infrared Camera (IRC) is one of the two instruments on board theAKARI satellite. In addition to deep imaging from 1.8 to 26.5 ×
| Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. II. 70 μm Imaging
The absolute calibration and characterization of the Multiband ImagingPhotometer for Spitzer (MIPS) 70 μm coarse- and fine-scale imagingmodes are presented based on over 2.5 yr of observations. Accuratephotometry (especially for faint sources) requires two simple processingsteps beyond the standard data reduction to remove long-term detectortransients. Point-spread function (PSF) fitting photometry is found togive more accurate flux densities than aperture photometry. Based on thePSF fitting photometry, the calibration factor shows no strong trendwith flux density, background, spectral type, exposure time, or timesince anneals. The coarse-scale calibration sample includes observationsof stars with flux densities from 22 mJy to 17 Jy, on backgrounds from 4to 26 MJy sr-1, and with spectral types from B to M. Thecoarse-scale calibration is 702+/-35 MJy sr-1MIPS70-1 (5% uncertainty) and is based on measurements of 66stars. The instrumental units of the MIPS 70 μm coarse- andfine-scale imaging modes are called MIPS70 and MIPS70F, respectively.The photometric repeatability is calculated to be 4.5% from two starsmeasured during every MIPS campaign and includes variations on alltimescales probed. The preliminary fine-scale calibration factor is2894+/-294 MJy sr-1 MIPS70F-1 (10% uncertainty)based on 10 stars. The uncertainties in the coarse- and fine-scalecalibration factors are dominated by the 4.5% photometric repeatabilityand the small sample size, respectively. The 5 σ, 500 ssensitivity of the coarse-scale observations is 6-8 mJy. This work showsthat the MIPS 70 μm array produces accurate, well-calibratedphotometry and validates the MIPS 70 μm operating strategy,especially the use of frequent stimulator flashes to track the changingresponsivities of the Ge:Ga detectors.
| Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. I. The Stellar Calibrator Sample and the 24 μm Calibration
We present the stellar calibrator sample and the conversion frominstrumental to physical units for the 24 μm channel of the MultibandImaging Photometer for Spitzer (MIPS). The primary calibrators are Astars, and the calibration factor based on those stars is4.54×10-2 MJy sr-1 (DNs-1)-1, with a nominal uncertainty of 2%. Wediscuss the data reduction procedures required to attain this accuracy;without these procedures, the calibration factor obtained using theautomated pipeline at the Spitzer Science Center is 1.6%+/-0.6% lower.We extend this work to predict 24 μm flux densities for a sample of238 stars that covers a larger range of flux densities and spectraltypes. We present a total of 348 measurements of 141 stars at 24 μm.This sample covers a factor of ~460 in 24 μm flux density, from 8.6mJy up to 4.0 Jy. We show that the calibration is linear over that rangewith respect to target flux and background level. The calibration isbased on observations made using 3 s exposures; a preliminary analysisshows that the calibration factor may be 1% and 2% lower for 10 and 30 sexposures, respectively. We also demonstrate that the calibration isvery stable: over the course of the mission, repeated measurements ofour routine calibrator, HD 159330, show a rms scatter of only 0.4%.Finally, we show that the point-spread function (PSF) is well measuredand allows us to calibrate extended sources accurately; InfraredAstronomy Satellite (IRAS) and MIPS measurements of a sample of nearbygalaxies are identical within the uncertainties.
| Spitzer Survey of the Large Magellanic Cloud: Surveying the Agents of a Galaxy's Evolution (SAGE). I. Overview and Initial Results
We are performing a uniform and unbiased imaging survey of the LargeMagellanic Cloud (LMC; ~7deg×7deg) using theIRAC (3.6, 4.5, 5.8, and 8 μm) and MIPS (24, 70, and 160 μm)instruments on board the Spitzer Space Telescope in the Surveying theAgents of a Galaxy's Evolution (SAGE) survey, these agents being theinterstellar medium (ISM) and stars in the LMC. This paper provides anoverview of the SAGE Legacy project, including observing strategy, dataprocessing, and initial results. Three key science goals determined thecoverage and depth of the survey. The detection of diffuse ISM withcolumn densities >1.2×1021 H cm-2 permits detailed studies of dust processes in the ISM. SAGE'spoint-source sensitivity enables a complete census of newly formed starswith masses >3 Msolar that will determine the current starformation rate in the LMC. SAGE's detection of evolved stars withmass-loss rates >1×10-8 Msolaryr-1 will quantify the rate at which evolved stars injectmass into the ISM of the LMC. The observing strategy includes two epochsin 2005, separated by 3 months, that both mitigate instrumentalartifacts and constrain source variability. The SAGE data arenonproprietary. The data processing includes IRAC and MIPS pipelines anda database for mining the point-source catalogs, which will be releasedto the community in support of Spitzer proposal cycles 4 and 5. Wepresent initial results on the epoch 1 data for a region near N79 andN83. The MIPS 70 and 160 μm images of the diffuse dust emission ofthe N79/N83 region reveal a similar distribution to the gas emissions,especially the H I 21 cm emission. The measured point-source sensitivityfor the epoch 1 data is consistent with expectations for the survey. Thepoint-source counts are highest for the IRAC 3.6 μm band and decreasedramatically toward longer wavelengths, consistent with the fact thatstars dominate the point-source catalogs and the dusty objects detectedat the longer wavelengths are rare in comparison. The SAGE epoch 1point-source catalog has ~4×106 sources, and more areanticipated when the epoch 1 and 2 data are combined. Using Milky Way(MW) templates as a guide, we adopt a simplified point-sourceclassification to identify three candidate groups-stars without dust,dusty evolved stars, and young stellar objects-that offer a startingpoint for this work. We outline a strategy for identifying foreground MWstars, which may comprise as much as 18% of the source list, andbackground galaxies, which may comprise ~12% of the source list.
| MSX, 2MASS, and the LARGE MAGELLANIC CLOUD: A Combined Near- and Mid-Infrared View
The Large Magellanic Cloud (LMC) has been observed by the MidcourseSpace Experiment (MSX) in the mid-infrared and the Two Micron All SkySurvey (2MASS) in the near-infrared. We have performed across-correlation of the 1806 MSX catalog sources and nearly 1.4 million2MASS cataloged point and extended sources and find 1664 matches. Usingthe available color information, we identify a number of stellarpopulations and nebulae, including main-sequence stars, giant stars, redsupergiants, carbon- and oxygen-rich asymptotic giant branch (AGB)stars, planetary nebulae, H II regions, and other dusty objects likelyassociated with early-type stars. A total of 731 of these sources haveno previous identification. We compile a listing of all objects, whichincludes photometry and astrometry. The 8.3 μm MSX sensitivity is thelimiting factor for object detection: only the brighter red objects,specifically the red supergiants, AGB stars, planetary nebulae, and H IIregions, are detected in the LMC. The remaining objects are likely inthe Galactic foreground. The spatial distribution of the infrared LMCsources may contribute to understanding stellar formation and evolutionand the overall galactic evolution. We demonstrate that a combined mid-and near-infrared photometric baseline provides a powerful means ofidentifying new objects in the LMC for future ground-based andspace-based follow-up observations.
| Positional reference stars in the Magellanic Clouds
The equatorial coordinates are determined of 926 stars (mainly ofgalactic origin) in the direction of the Magellanic Clouds at the meanepoch T = 1978.4 with an overall accuracy characterized by the meanvalues of the O-C coordinates, Sa = 0.35 arcsec and Sd = 0.38 arcsec,calculated from the coordinates of the Perth reference stars. Thesevalues are larger than the accuracy expected for primary standard stars.They allow the new positions to be considered as those of reliablesecondary standard stars. The published positions correspond to anunquestionable improvement of the quality of the coordinates provided inthe current catalogs. This study represents an 'astrometric step' in thestarting of a 'Durchmusterung' of the Magellanic Clouds organized by deBoer (1988, 1989).
| Hyades and Sirius supercluster members brighter than magnitude (V) 7.1. II - Right ascension six to twelve hours
The present star sample is contained in the Bright Star Catalogue andits Supplement, augmented with a further supplement of 788 stars foundduring various observing programs over the past 40 years. Accurate,four-color and H-beta, or (RI), photometry is available for most of thesupercluster members. The criteria for membership are the comparisons ofthe proper motion, radial velocity, and luminosity obtained from thesupercluster parameters with the observed motions and the luminosityderived from the photometric parameters. New proper motions, based onall available catalogs, have been derived for the additional 788 starsdiscussed here, as well as all supercluster members.
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