Showing papers by "Joseph L. Hora published in 2005"
TL;DR: The Infrared Array Camera (IRAC) on the Spitzer Space Telescope is absolutely calibrated by comparing photometry of a set of A stars near the north ecliptic pole to predictions based on ground-based observations and a stellar atmosphere model as mentioned in this paper.
Abstract: The Infrared Array Camera (IRAC) on the Spitzer Space Telescope is absolutely calibrated by comparing photometry of a set of A stars near the north ecliptic pole to predictions based on ground‐based observations and a stellar atmosphere model The brightness of point sources is calibrated to an accuracy of 3%, relative to models for A‐star stellar atmospheres, for observations performed and analyzed in the same manner as for the calibration stars This includes corrections for the location of the star in the array and the location of the centroid within the peak pixel Long‐term stability of the IRAC photometry was measured by monitoring the brightness of A dwarfs and K giants (near the north ecliptic pole) observed several times per month; the photometry is stable to 15% (rms) over a year Intermediate‐timescale stability of the IRAC photometry was measured by monitoring at least one secondary calibrator (near the ecliptic plane) every 12 hr while IRAC was in nominal operations; the intermediat
681 citations
TL;DR: The Infrared Array Camera (IRAC) on the Spitzer Space Telescope is absolutely calibrated by comparing photometry on a set of A stars near the north ecliptic pole to predictions based on ground-based observations and a stellar atmosphere model as discussed by the authors.
Abstract: The Infrared Array Camera (IRAC) on the Spitzer Space Telescope is absolutely calibrated by comparing photometry on a set of A stars near the north ecliptic pole to predictions based on ground-based observations and a stellar atmosphere model. The brightness of point sources is calibrated to an accuracy of 3%, relative to models for A star stellar atmospheres, for observations performed and analyzed in the same manner as the calibration stars. This includes corrections for location of the star in the array and the location if the centroid within the peak pixel. Long-term stability of the IRAC photometry was measured by monitoring the brightness of A dwarfs and K giants (near the north ecliptic pole) observed several times per month; the photometry is stable to 1.5% (rms) over a year. Intermediate-time-scale stability of the IRAC photometry was measured by monitoring at least one secondary calibrator (near the ecliptic plane) every 12 hr while IRAC is in nominal operations; the intermediate-term photometry is stable with a 1% dispersion (rms). One of the secondary calibrators was found to have significantly time-variable (5%) mid-infrared emission, with period (7.4 days) matching the optical light curve; it is possibly a Cepheid variable.
43 citations
01 Jun 2005
TL;DR: Meixner et al. as mentioned in this paper proposed the Meixner Space Telescope Science Institute (MSCI) and the SAGE Team Space Telescope science Institute (SAWSI) for the first time.
Abstract: M. Meixner1, K. Gordon2, R. Indebetouw3, B. Whitney4, M. Meade5, B. Babler5, J. Hora6, U. Vijh1, S. Srinivasan1, C. Leitherer1, M. Sewilo5, C. Engelbracht2, M. Block2, B. For7, R. Blum8, W. Reach9, J-P. Bernard10 and the SAGE Team Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA email: meixner@stsci.edu University of Arizona, University of Virgina, Space Sciences Institute, University of Wisconsin, Harvard/CfA, University of Texas, NOAO/Tucson, Spitzer Science Center, CESR
37 citations
01 May 2005
TL;DR: In this article, a survey of several regions of high-mass star formation is conducted to assess their content and structure using Spitzer observations, ground-based optical and near-IR imaging surveys, and optical and IR spectra of objects and locations in the molecular clouds.
Abstract: We are conducting a survey of several regions of high-mass star formation to assess their content and structure. The observations include Spitzer observations, ground-based optical and near-IR imaging surveys, and optical and IR spectra of objects and locations in the molecular clouds. The goal of the survey is to gain a better understanding of the processes involved in high mass star formation by determining the characteristics of the stars detected in these regions and investigating the properties of the interstellar medium (ISM) environment in which these stars form. In this contribution, we present results on the identication and spatial analysis of young stars in three clusters, W5/AFGL 4029, S255, and S235. First we show how the IRAC data are used to roughly segregate young stars according to their mid-infrared colors, into two groups corresponding the SED Class I and Class II young stellar objects. Then using the IRAC data in combination with 2MASS, we show how more young stars can be identied. Finally, we examine the spatial distributions of young stars in these clusters and nd a range of morphologies and of peak surface densities.
17 citations
TL;DR: In this article, a survey of several regions of high-mass star formation is conducted to assess their content and structure using Spitzer observations, ground-based optical and near-IR imaging surveys, and optical and IR spectra of objects and locations in the molecular clouds.
Abstract: We are conducting a survey of several regions of high-mass star formation to assess their content and structure. The observations include Spitzer observations, ground-based optical and near-IR imaging surveys, and optical and IR spectra of objects and locations in the molecular clouds. The goal of the survey is to gain a better understanding of the processes involved in high mass star formation by determining the characteristics of the stars detected in these regions and investigating the properties of the interstellar medium (ISM) environment in which these stars form. In this contribution, we present results on the identification and spatial analysis of young stars in three clusters, W5/AFGL 4029, S255, and S235. First we show how the IRAC data are used to roughly segregate young stars according to their mid-infrared colors, into two groups corresponding the SED Class I and Class II young stellar objects. Then using the IRAC data in combination with 2MASS, we show how more young stars can be identified. Finally, we examine the spatial distributions of young stars in these clusters and find a range of morphologies and of peak surface densities.
15 citations
TL;DR: In this article, a survey of the Orion A and B molecular clouds made with the InfraRed Array Camera (IRAC) onboard the Spitzer Space Telescope is presented, which covers a number of known star forming regions, from the massive star forming clusters in the Orion Nebula and NGC 2024 to small groups of low mass stars in the L1641.
Abstract: We present initial results from a survey of the Orion A and B molecular clouds made with the InfraRed Array Camera (IRAC) onboard the Spitzer Space Telescope. This survey encompasses a total of 5.6 square degrees with the sensitivity to detect objects below the hydrogen burning limit at an age of 1 Myr. These observations cover a number of known star forming regions, from the massive star forming clusters in the Orion Nebula and NGC 2024, to small groups of low mass stars in the L1641. We combine the IRAC photometry with photometry from the 2MASS point source catalog and use the resulting seven band data to identify stars with infrared excesses due to dusty disks and envelopes. Using the presence of an infrared excess as an indicator of youth, we show the distribution of young stars and protostars in the two molecular clouds. We find that roughly half of the stars are found in dense clusters surrounding the two regions of recent massive star formation in the Orion clouds, NGC 2024 and the Orion Nebula.
8 citations
01 Aug 2005
2 citations
01 Jan 2005
TL;DR: Patten et al. as mentioned in this paper presented a survey of the state-of-the-art work in the field of astrophysics with the Spitzer/IRAC IRAC project.
Abstract: WITH SPITZER/IRAC. Brian M. Patten, Kevin L. Luhman, Joseph L. Hora, Massimo Marengo, Michael T. Schuster, Sarah M. Sonnett, Richard G. Ellis, John R. Stauffer, and Giovanni G. Fazio, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA, USA 02138, (bpatten@cfa.harvard.edu), Pennsylvania State University, 525 Davey Lab, University Park, PA USA 16802, University of Minnesota, 116 Church St., Minneapolis, MN USA 55455, Spitzer Science Center, MS-220-6, Caltech, Pasadena, CA, USA 91125.
2 citations
01 Dec 2005
1 citations
01 Aug 2005
1 citations