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تسجيل مستخدم جديدThe Formation and Evolution of Planetary Systems: Description of the Spitzer Legacy Science Database
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We present the science database produced by the Formation and Evolution of Planetary Systems (FEPS) Spitzer Legacy program. Data reduction and validation procedures for the IRAC, MIPS, and IRS instruments are described in detail. We also derive stellar properties for the FEPS sample from available broad-band photometry and spectral types, and present an algorithm to normalize Kurucz synthetic spectra to optical and near-infrared photometry. The final FEPS data products include IRAC and MIPS photometry for each star in the FEPS sample and calibrated IRS spectra.
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We present 3-160 micron photometry obtained with the IRAC and MIPS instruments for the first five targets from the Spitzer Legacy Science Program Formation and Evolution of Planetary Systems and 4-35 micron spectro-photometry obtained with the IRS fo
r two sources. We discuss in detail our observations of the debris disks surrounding HD 105 (G0V, 30 +- 10 Myr) and HD 150706 (G3V, ~ 700 +- 300 Myr). For HD 105, possible interpretations include large bodies clearing the dust inside of 45 AU or a reservoir of gas capable of sculpting the dust distribution. The disk surrounding HD 150706 also exhibits evidence of a large inner hole in its dust distribution. Of the four survey targets without previously detected IR excess, spanning ages 30 Myr to 3 Gyr, the new detection of excess in just one system of intermediate age suggests a variety of initial conditions or divergent evolutionary paths for debris disk systems orbiting solar-type stars.
We will utilize the sensitivity of SIRTF through the Legacy Science Program to carry out spectrophotometric observations of solar-type stars aimed at (1) defining the timescales over which terrestrial and gas giant planets are built, from measurement
s diagnostic of dust/gas masses and radial distributions; and (2) establishing the diversity of planetary architectures and the frequency of planetesimal collisions as a function of time through observations of circumstellar debris disks. Together, these observations will provide an astronomical context for understanding whether our solar system - and its habitable planet - is a common or a rare circumstance. Achieving our science goals requires measuring precise spectral energy distributions for a statistically robust sample capable of revealing evolutionary trends and the diversity of system outcomes. Our targets have been selected from two carefully assembled databases of solar-like stars: (1) a sample located within 50 pc of the Sun spanning an age range from 100-3000 Myr for which a rich set of ancillary measurements (e.g. metallicity, stellar activity, kinematics) are available; and (2) a selection located between 15 and 180 pc and spanning ages from 3 to 100 Myr. For stars at these distances SIRTF is capable of detecting stellar photospheres with SNR >30 at lambda < 24 microns for our entire sample, as well as achieving SNR >5 at the photospheric limit for over 50% of our sample at lambda=70 microns. Thus we will provide a complete census of stars with excess emission down to the level produced by the dust in our present-day solar system. More information concerning our program can be found at: http://gould.as.arizona.edu/feps
(abbreviated) We report detection with the Spitzer Space Telescope of cool dust surrounding solar type stars. The observations were performed as part of the Legacy Science Program, ``Formation and Evolution of Planetary Systems (FEPS). From the overa
ll FEPS sample (Meyer et al. 2006) of 328 stars having ages ~0.003-3 Gyr we have selected sources with 70 um flux densities indicating excess in their spectral energy distributions above expected photospheric emission........ .....The rising spectral energy distributions towards - and perhaps beyond - 70 um imply dust temperatures T_dust <45-85 K for debris in equilibrium with the stellar radiation field. We infer bulk properties such as characteristic temperature, location, fractional luminosity, and mass of the dust from fitted single temperature blackbody models. For >1/3 of the debris sources we find that multiple temperature components are suggested, implying a spatial distribution of dust extending over many tens of AU. Because the disks are dominated by collisional processes, the parent body (planetesimal) belts may be extended as well. Preliminary assessment of the statistics of cold debris around sun-like stars shows that ~10% of FEPS targets with masses between 0.6 and 1.8 Msun and ages between 30 Myr and 3 Gyr exhibit 70 um emission in excess of the expected photospheric flux density. We find that fractional excess amplitudes appear higher for younger stars and that there may be a trend in 70 um excess frequency with stellar mass.
We provide an overview of the Spitzer Legacy Program ``Formation and Evolution of Planetary Systems (FEPS) which was proposed in 2000, begun in 2001, and executed aboard the Spitzer Space Telescope between 2003 and 2006. This program exploits the sen
sitivity of Spitzer to carry out mid-infrared spectrophotometric observations of solar-type stars. With a sample of ~ 328 stars ranging in age from ~ 3 Myr to ~ 3 Gyr, we trace the evolution of circumstellar gas and dust from primordial planet-building stages in young circumstellar disks through to older collisionally generated debris disks. When completed, our program will help define the time scales over which terrestrial and gas giant planets are built, constrain the frequency of planetesimal collisions as a function of time, and establish the diversity of mature planetary architectures. In addition to the observational program, we have coordinated a concomitant theoretical effort aimed at understanding the dynamics of circumstellar dust with and without the effects of embedded planets, dust spectral energy distributions, and atomic and molecular gas line emission. Together with the observations, these efforts will provide astronomical context for understanding whether our Solar System - and its habitable planet - is a common or a rare circumstance. Additional information about the FEPS project can be found on the team website: feps.as.arizona.edu
Stars and planets are the fundamental objects of the Universe. Their formation processes, though related, may differ in important ways. Stars almost certainly form from gravitational collapse and probably have formed this way since the first stars li
t the skies. Although it is possible that planets form in this way also, processes involving accretion in a circumstellar disk have been favored. High fidelity high resolution images may resolve the question; both processes may occur in some mass ranges. The questions to be answered in the next decade include: By what process do planets form, and how does the mode of formation determine the character of planetary systems? What is the distribution of masses of planets? In what manner does the metallicity of the parent star influence the character of its planetary system? In this paper we discuss the observations of planetary systems from birth to maturity, with an emphasis on observations longward of 100 $mu$m which may illuminate the character of their formation and evolution. Advantages of this spectral region include lower opacity, availability of extremely high resolution to reach planet formation scales and to perform precision astrometry and high sensitivity to thermal emission.
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