c2d<i>Spitzer</i>IRS spectra of embedded low-mass young stars: gas-phase emission lines

Lahuis, F.; Dishoeck, E. F. van; Jørgensen, J. K.; Blake, Geoffrey A.; Evans, Neal J.

doi:10.1051/0004-6361/200913957

Cited by 23 publications

(28 citation statements)

References 92 publications

(138 reference statements)

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“…The rms of the continuum increases with L IR , but the signal-to-noise ratio for the detected [Ne II] lines is distributed uniformly over the L IR spanned by our sample, with no preference for either high or low values of the signal-to noise ratio. This correlation was also found by Lahuis et al (2010) in a sample of Class I sources. We have tested the correlation between the luminosity of the [Ne II] line and the luminosity of the [O I] line at 6300 Å compiled from the literature, obtaining a positive result.…”

Section: Correlations With Accretion Parameterssupporting

confidence: 74%

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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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Section: Correlations With Accretion Parameterssupporting

confidence: 74%

“…The sample from Güdel et al (2010) did not contain any Class I or Herbig AeBe stars. Furthermore, their data reduction differed from ours, as they used the method introduced in Lahuis et al (2010) in which the compact and extended component of the line emission are separated during the spectral extraction procedure.…”

Section: [Ne Ii] Emissionmentioning

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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“…As we show below, our observations suggest the presence of both fast and slow shocks in Serpens SMM1. Lahuis et al 2010, for the c2d Spitzer sample). Hollenbach & McKee (1989) presented detailed models for the fine-structure emission of atoms and ions in such dissociative J-type shocks.…”

Section: Shocked-gas Componentsmentioning

confidence: 99%

The complete far-infrared and submillimeter spectrum of the Class 0 protostar Serpens SMM1 obtained withHerschel

Goicoechea¹,

Cernicharo²,

Karska³

et al. 2012

A&A

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161

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We present the first complete ∼55−671 μm spectral scan of a low-mass Class 0 protostar (Serpens SMM1) taken with the PACS and SPIRE spectrometers onboard Herschel. More than 145 lines have been detected, most of them rotationally excited lines of 12 CO (full ladder from J u = 4−3 to 42−41 and E u /k = 4971 K), H 2 O (up to 8 18 −7 07 and E u /k = 1036 K), OH (up to 2 Π 1/2 J = 7/2−5/2 and E u /k = 618 K), 13

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“…Spitzer observations were retrieved from the Spitzer Heritage Archive (SHA) 1 program (Evans et al 2003(Evans et al , 2009Lahuis et al 2010). In these data, the low resolution (R ∼ 60-120) modules, short-low (SL) and long-low (LL), of the Spitzer infrared spectrograph (IRS, Houck et al 2004) were employed, providing a complete wavelength coverage between 5.2 and 38.0 μm.…”

Section: Spitzer/irsmentioning

confidence: 99%

Dust, ice and gas in time (DIGIT):HerschelandSpitzerspectro-imaging of SMM3 and SMM4 in Serpens

Dionatos

Jørgensen

Green

et al. 2013

A&A

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Context. Mid-and far-infrared observations of the environment around embedded protostars reveal a plethora of high excitation molecular and atomic emission lines. Different mechanisms for the origin of these lines have been proposed, including shocks induced by protostellar jets and radiation or heating by the embedded protostar of its immediate surroundings. Aims. By studying of the most important molecular and atomic coolants, we aim at constraining the physical conditions around the embedded protostars SMM3 and SMM4 in the Serpens molecular cloud core and measuring the CO/H 2 ratio in warm gas. The excitation conditions for molecular species are assessed through rotational diagrams. Emission lines from major coolants are compared to the results of steady-state C-and J-type shock models. Results. Line emission tends to peak at distances of ∼10-20 from the protostellar sources with all but [CII] peaking at the positions of outflow shocks seen in near-IR and sub-millimeter interferometric observations. The [CII] emission pattern suggests that it is most likely excited from energetic UV radiation originating from the nearby flat-spectrum source SMM6. Excitation analysis indicates that H 2 and CO originate in gas at two distinct rotational temperatures of ∼300 K and 1000 K, while the excitation temperature for H 2 O and OH is ∼100-200 K. The morphological and physical association between CO and H 2 suggests a common excitation mechanism, which allows direct comparisons between the two molecules. The CO/H 2 abundance ratio varies from ∼10 −5 in the warmer gas up to ∼10 −4 in the hotter regions. Shock models indicate that C-shocks can account for the observed line intensities if a beam filling factor and a temperature stratification in the shock front are considered. C-type shocks can best explain the emission from H 2 O. The existence of J-shocks is suggested by the strong atomic/ionic (except for [CII]) emission and a number of line ratio diagnostics. Dissociative shocks can account for the CO and H 2 emission in a single excitation temperature structure. Conclusions. The bulk of cooling from molecular and atomic lines is associated with gas excited in outflow shocks. The strong association between H 2 and CO constrain their abundance ratio in warm gas. Both C-and J-type shocks can account for the observed molecular emission; however, J-shocks are strongly suggested by the atomic emission and provide simpler and more homogeneous solutions for CO and H 2 . The variations in the CO/H 2 abundance ratio for gas at different temperatures can be interpreted by their reformation rates in dissociative J-type shocks, or the influence of both C and J shocks.

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c2dSpitzerIRS spectra of embedded low-mass young stars: gas-phase emission lines

Cited by 23 publications

References 92 publications

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

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

The complete far-infrared and submillimeter spectrum of the Class 0 protostar Serpens SMM1 obtained withHerschel

Dust, ice and gas in time (DIGIT):HerschelandSpitzerspectro-imaging of SMM3 and SMM4 in Serpens

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