Mid‐infrared Spectra of Class I Protostars in Taurus

Watson, D. M.; Kemper, F.; Calvet, Nuria; Keller, L. D.; Furlan, Elise; Hartmann, L.; Forrest, W. J.; Chen, Christine; Uchida, K. I.; Green, Joel D.; Sargent, B.; Sloan, G. C.; Herter, T.; Brandl, Bernhard R.; Houck, J. R.; Najita, J.; D’Alessio, Paola; Myers, P. C.; Barry, D. J.; Hall, Peter; Morris, P.

doi:10.1086/422918

Cited by 59 publications

(38 citation statements)

References 27 publications

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“…Our observations suggest that the disk is much smaller than that, although still quite large compared to typical protoplanetary disks. Moreover, the infrared spectrum exhibits absorption features of H 2 O and CO 2 ices and a silicate absorption feature, all of which are more commonly associated with Class I sources embedded in envelopes (e.g., Watson et al 2004;Pontoppidan et al 2008). The presence of these features, along with the good fit of our disk+envelope model to the combined SED and millimeter visibilities, suggests that this is an embedded source.…”

Section: Iras 04158+2805mentioning

confidence: 64%

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Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

Sheehan

Eisner

2017

ApJ

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Class I protostars are thought to represent an early stage in the lifetime of protoplanetary disks, when they are still embedded in their natal envelope. Here we measure the disk masses of 10 Class I protostars in the Taurus Molecular Cloud to constrain the initial mass budget for forming planets in disks. We use radiative transfer modeling to produce synthetic protostar observations and fit the models to a multi-wavelength data set using a Markov Chain Monte Carlo fitting procedure. We fit these models simultaneously to our new Combined Array for Research in Millimeter-wave Astronomy 1.3 mm observations that are sensitive to the wide range of spatial scales that are expected from protostellar disks and envelopes so as to be able to distinguish each component, as well as broadband spectral energy distributions compiled from the literature. We find a median disk mass of  M 0.018 on average, more massive than the Taurus Class II disks, which have median disk mass of~ M 0.0025 . This decrease in disk mass can be explained if dust grains have grown by a factor of 75 in grain size, indicating that by the Class II stage, at a few Myr, a significant amount of dust grain processing has occurred. However, there is evidence that significant dust processing has occurred even during the Class I stage, so it is likely that the initial mass budget is higher than the value quoted here.

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Section: Iras 04158+2805mentioning

confidence: 64%

“…Furthermore, all of our targets have been observed with the Spitzer IRS spectrograph, and most have silicate and/or CO 2 ice absorption in their spectra, commonly associated with embedded sources (e.g., Alexander et al 2003;Boogert et al 2004;Watson et al 2004;Pontoppidan et al 2008). …”

Section: Sample Selectionmentioning

confidence: 99%

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

Sheehan

Eisner

2017

ApJ

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“…This last feature is detected in absorption in all sources except #7 and #18, where it is observed in emission, usually indicating more evolved objects (see, e.g., Watson et al 2004). These broadband features are usually connected to dust and ice mantels on dust in the interstellar medium and in the YSO envelope, and their optical depths have been used in several works to compute extinction towards the protostellar photospheres (see, e.g., Alexander et al 2003;Chiar et al 2007).…”

Section: Spitzer Irs Spectramentioning

confidence: 83%

POISSON project

Garatti

Lopez

Antoniucci

et al. 2012

A&A

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Context. Characterising stellar and circumstellar properties of embedded young stellar objects (YSOs) is mandatory for understanding the early stages of the stellar evolution. This task requires the combination of both spectroscopy and photometry, covering the widest possible wavelength range, to disentangle the various protostellar components and activities. Aims. As part of the POISSON project (Protostellar Optical-Infrared Spectral Survey On NTT), we present a multi-wavelength spectroscopic and photometric investigation of embedded YSOs in L 1641, aimed to derive the stellar parameters and evolutionary stages and to infer their accretion properties. Methods. Our multi-wavelength database includes low-resolution optical-IR spectra from the NTT and Spitzer (0.6−40 μm) and photometric data covering a spectral range from 0.4 to 1100 μm, which allow us to construct the YSOs spectral energy distributions (SEDs) and to infer the main stellar parameters (visual extinction, spectral type, accretion, stellar, bolometric luminosity, mass accretion, and ejection rates). Results. The NTT optical-NIR spectra are rich in emission lines, which are mostly associated with YSO accretion, ejection, and chromospheric activities. A few emission lines, prominent ice (H 2 O and CO 2 ), and amorphous silicate absorption features have also been detected in the Spitzer spectra. The SED analysis allows us to group our 27 YSOs into nine Class I, eleven Flat, and seven Class II objects. However, on the basis of the derived stellar properties, only six Class I YSOs have an age of ∼10 5 yr, while the others are older (5 × 10 5 −10 6 yr), and, among the Flat sources, three out of eleven are more evolved objects (5 × 10 6 −10 7 yr), indicating that geometrical effects can significantly modify the SED shapes. Inferred mass accretion rates (Ṁ acc ) show a wide range of values (3.6 × 10 −9 to 1.2 × 10 −5 M yr −1 ), which reflects the age spread observed in our sample well. Average values of mass accretion rates, extinction, and spectral indices decrease with the YSO class. The youngest YSOs have the highestṀ acc , whereas the oldest YSOs do not show any detectable jet activity in either images and spectra. Apart from the outbursting source #25 and, marginally, #20, none of the remaining YSOs is accretion-dominated (L acc > L * ). We also observe a clear correlation among the YSOṀ acc , M * , and age. For YSOs with t > 10 5 yr and 0.4 M ≤ M * ≤ 1.2 M , a relationship betweenṀ acc and t (Ṁ acc ∝ t −1.2 ) has been inferred, consistent with mass accretion evolution in viscous disc models and indicating that the mass accretion decay is slower than previously assumed. Finally, our results suggest that episodic outbursts are required for Class I YSOs to reach typical classical T Tauri stars stellar masses.

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“…Most of the targets studied belong to GTO (Guaranteed Time Observations) programs; several publications exist that focussed on the study of the silicate and ice features (e.g., Watson et al 2004;Furlan et al 2006;Furlan et al 2008). In particular, we used data from the GTO program number 2, from the Legacy programs 171, 179, and from the GO (General Observer) programs 3470, 3716, and 30300.…”

Section: Samplementioning

confidence: 99%

Searching for gas emission lines inSpitzerInfrared Spectrograph (IRS) spectra of young stars in Taurus

Baldovin-Saavedra

Audard

Güdel

et al. 2011

A&A

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Context. Our knowledge of circumstellar disks has traditionally been based on studies of dust. However, gas dominates the disk mass and its study is key to our understanding of accretion, outflows, and ultimately planet formation. The Spitzer Space Telescope provides access to gas emission lines in the mid-infrared, providing crucial new diagnostics of the physical conditions in accretion disks and outflows. Aims. We seek to identify gas emission lines in mid-infrared spectra of 64 pre-main-sequence stars in Taurus. Using line luminosities and other known star-disk-outflow parameters, we aim to identify correlations that will help to constrain gas heating, excitation mechanisms, and the line formation. Methods. We have based our study on Spitzer observations using the Infrared Spectrograph (IRS), mainly with the high-resolution modules. Line luminosities (or 3σ upper limits) have been obtained by fitting Gaussian profiles to the lines. We have further searched for correlations between the line luminosities and different parameters related to the star-disk system. Results. We have detected H 2 (17.03, 28.22 μm) emission in 6 objects, [Ne II] (12.81 μm) emission in 18 objects, and [Fe II] (17.93, 25.99 μm) emission in 7 objects. [Ne II] detections are found primarily in Class II objects. The luminosity of the [Ne II] line (L NeII ) is in general higher for objects known to drive jets than for those without known jets, but the two groups are not statistically distinguishable. L NeII is correlated with X-ray luminosity, but for Class II objects only. L NeII is also correlated with disk mass and accretion rate when the sample is divided into high and low accretors. Furthermore, we find correlations of L NeII with mid-IR continuum luminosity and with luminosity of the [O I] (6300 Å) line, the latter being an outflow tracer. L [FeII] correlates withṀ acc . No correlations were found between L H 2 and several tested parameters. Conclusions. Our study reveals a general trend toward accretion-related phenomena as the origin of the gas emission lines. Shocks in jets and outflowing material are more likely to play a significant role than shocks in infalling material. The role of X-ray irradiation is less prominent but still present for [Ne II], in particular for Class II sources, while the lack of correlation between [Fe II] and [Ne II] points toward different emitting mechanisms.

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Mid‐infrared Spectra of Class I Protostars in Taurus

Cited by 59 publications

References 27 publications

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

POISSON project

Searching for gas emission lines inSpitzerInfrared Spectrograph (IRS) spectra of young stars in Taurus

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