Interpreting Spectral Energy Distributions from Young Stellar Objects. I. A Grid of 200,000 YSO Model SEDs

By Thomas Robitaille, B. Whitney, R. Indebetouw, K. Wood, P. Denzmore. 2006

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We present a grid of radiation transfer models of axisymmetric young stellar objects (YSOs), covering a wide range of stellar masses (from 0.1 to 50 M☉) and evolutionary stages (from the early envelope infall stage to the late disk-only stage). The grid consists of 20,000 YSO models, with spectral energy distributions (SEDs) and polarization spectra computed at 10 viewing angles for each model, resulting in a total of 200,000 SEDs. We have made a careful assessment of the theoretical and observational constraints on the physical conditions of disks and envelopes in YSOs and have attempted to fully span the corresponding regions in parameter space. These models are publicly available on a dedicated Web server. In this paper we summarize the main features of our models, as well as the range of parameters explored. Having a large grid covering reasonable regions of parameter space allows us to shed light on many trends in near- and mid-IR observations of YSOs (such as changes in the spectral indices and colors of their SEDs), linking them with physical parameters (such as disk and infalling envelope parameters). In particular, we examine the dependence of the spectral indices of the model SEDs on envelope accretion rate and disk mass. In addition, we show variations of spectral indices with stellar temperature, disk inner radius, and disk flaring power for a subset of disk-only models. We also examine how changing the wavelength range of data used to calculate spectral indices affects their values. We show sample color-color plots of the entire grid as well as simulated clusters at various distances with typical Spitzer sensitivities. We find that young embedded sources generally occupy a large region of color-color space due to inclination and stellar temperature effects. Disk sources occupy a smaller region of color-color space but overlap substantially with the region occupied by embedded sources, especially in the near- and mid-IR. We identify regions in color-color space where our models indicate that only sources at a given evolutionary stage should lie. We find that, while near-IR (such as JHK) and mid-IR (such as IRAC) fluxes are useful in discriminating between stars and YSOs, and are useful for identifying very young sources, the addition of longer wavelength data such as MIPS 24 μm is extremely valuable for determining the evolutionary stage of YSOs.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/87ced50c5b5ef3662e751f6fd67d7f219dcd3c36

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Citations in the corpus

The Bubbling Galactic Disk. II. The Inner 20° (2007, background): “Observations (Allen et al. 2004) and theory (Robitaille et al. 2006) predict that YSOs have steeply rising spectral energy distributions from 8 to 24 m, and hence 8Y24 m colors should be an effective discriminator of YSOs.”
SPITZER SAGE SURVEY OF THE LARGE MAGELLANIC CLOUD. III. STAR FORMATION AND ∼1000 NEW CANDIDATE YOUNG STELLAR OBJECTS (2008, methodology): “Robitaille et al. (2006) computed a grid of 20,000 2D radiation transfer models intended to cover the full range of stellar masses and evolutionary stages of YSOs.”
LIME - a flexible, non-LTE line excitation and radiation transfer method for millimeter and far-infrared wavelengths (2010, neutral): “Such models are numerously found in the literature (e.g., Chiang & Goldreich 1997; Dullemond & Dominik 2004; Robitaille et al. 2006) but here we use a simple analytic toy model for illustrative purposes.”
THE EFFECTS OF RADIATIVE TRANSFER ON LOW-MASS STAR FORMATION (2009, background): “Typical pre-main sequence protostellar radii are expected to range from 3-5 R⊙ for low-mass stars (Palla & Stahler 1993; Robitaille et al. 2006).”
ATLASGAL — towards a complete sample of massive star forming clumps ⋆ (2014, background): “The fitter searches through 20 000 models which probe a range of properties of both the central (proto)star and surrounding material (Robitaille et al. 2006), each of which can be viewed from 10 different viewing angles, resulting in possible 200 000 SEDs.”
STAR FORMATION IN THE CENTRAL 400 PC OF THE MILKY WAY: EVIDENCE FOR A POPULATION OF MASSIVE YOUNG STELLAR OBJECTS (2009, methodology): “The SEDs of the sources are analyzed by comparing to a set of SEDs produced by a large grid of YSO models (Robitaille et al. 2006; Whitney et al. 2003b,a).”
A CATALOG OF EXTENDED GREEN OBJECTS IN THE GLIMPSE SURVEY: A NEW SAMPLE OF MASSIVE YOUNG STELLAR OBJECT OUTFLOW CANDIDATES (2008, background): “Figure 13 shows that EGOs are found in the region of colorcolor space occupied by very young YSOs, surrounded by substantial accreting envelopes (Robitaille et al. 2006).”
HIGH- AND INTERMEDIATE-MASS YOUNG STELLAR OBJECTS IN THE LARGE MAGELLANIC CLOUD (2009, methodology): “The SAGE YSOs are initially identified using a complex set of color and magnitude criteria based on the predictions from a grid of radiative transfer models that attempt to simulate the emission from YSOs (Whitney et al. 2003a, 2003b; Robitaille et al. 2006).”
Our astrochemical heritage (2012, methodology): “The approximate structure of the envelope, as derived by observations of the continuum and line emission (e.g. Ceccarelli et al. 2000a; Jørgensen et al. 2002; Robitaille et al. 2006) is reported in Fig.”
INTRINSICALLY RED SOURCES OBSERVED BY SPITZER IN THE GALACTIC MIDPLANE (2008, methodology): “For YSOs, the models from Robitaille et al. (2006) were used.”
A PARAMETRIC MODELING APPROACH TO MEASURING THE GAS MASSES OF CIRCUMSTELLAR DISKS (2013, methodology): “This approach is similar to the SED modeling of young stellar objects by Robitaille et al. (2006) and is also motivated by the grid modeling of mostly fine structure, far-infrared lines of atomic species for comparison with Herschel observations (Woitke et al. 2010; Kamp et al. 2011).”
THE HERSCHEL ORION PROTOSTAR SURVEY: SPECTRAL ENERGY DISTRIBUTIONS AND FITS USING A GRID OF PROTOSTELLAR MODELS (2016, background): “These observational classes are inferred to reflect evolutionary stages, with the inclination angle to the line of sight being the major source of uncertainty in translating classes to “stages” (Robitaille et al. 2006; Evans et al. 2009).”
DUST FILTRATION BY PLANET-INDUCED GAP EDGES: IMPLICATIONS FOR TRANSITIONAL DISKS (2012, methodology): “Monte-Carlo radiative transfer set-up The Monte Carlo radiative transfer code was developed by Whitney et al. (2003a,b), Robitaille et al. (2006), and Whitney et al. (2012), while for the disk structure see Whitney et al. (2003b) for references.”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “There are several alternative quantitative definitions of the qualitative terms used here (Robitaille et al. 2006; Crapsi et al. 2008).”
Dust Evolution and the Formation of Planetesimals (2016, background): “Even web-based SED fitting tools, built upon those codes are available (Robitaille et al. 2006; Robitaille et al. 2007).”
The simultaneous formation of massive stars and stellar clusters (2009, methodology): “Additionally, we approximate the radiative feedback from the newly formed stars by way of a grid of previously computed Monte Carlo radiative transfer models of young stars (Robitaille et al. 2006).”
EVOLUTIONARY SIGNATURES IN THE FORMATION OF LOW-MASS PROTOSTARS. II. TOWARD RECONCILING MODELS AND OBSERVATIONS (2005, background): “D models of embedded protostars that include disks (e.g., Whitney et al. 2003a; Whitney et al. 2003b; Robitaille et al. 2006; Crapsi et al. 2008).”
Identifying the Low-Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores (2007, background): “D models of sources (e.g., Whitney et al. 2003a; Whitney et al. 2003b; Robitaille et al. 2006) shows that, even at the most extreme pole-on inclinations, the effects of outflow cavities are unlikely to result in an observed SED more luminous in the near-infrared than at 24 and 70 µm.”
A CLASS I AND CLASS II CH3OH MASER SURVEY OF EGOs FROM THE GLIMPSE SURVEY (2009, background): “1 and Table 5), as expected for MYSOs (e.g. Robitaille et al. 2006; Carey et al. 2009).”