The complete far-infrared and submillimeter spectrum of the Class 0 protostar Serpens SMM1 obtained with<i>Herschel</i>

Goicoechea, J. R.; Cernicharo, J.; Karska, A.; Herczeg, Gregory J.; Polehampton, E. T.; Wampfler, S. F.; Kristensen, L. E.; Dishoeck, E. F. van; Etxaluze, M.; Berné, O.; Visser, R.

doi:10.1051/0004-6361/201219912

Cited by 89 publications

(189 citation statements)

References 60 publications

(108 reference statements)

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“…Neufeld (2012) has demonstrated that the excitation pattern of CO at a single kinetic temperature shows a broken power-law pattern that can reproduce the observed A88, page 10 of 22 distribution at sufficiently high temperatures and for densities below the critical density. This possibility has been examined for SMM1 in Serpens and B335, which display a similar excitation pattern to the Serpens sources of this work (Goicoechea et al 2012;Green et al 2013, respectively). In both cases, they find that solutions can be obtained for n(H 2 ) = 10 4 cm −3 and T ∼ 3000 K. While low densities are predicted by shock models (Sect.…”

Section: Excitation Conditionsmentioning

confidence: 62%

“…Reported column densities are about 2 orders of magnitude higher for both the warm and hot components in SMM1 than corresponding ones reported here. This difference can be interpreted in terms of the smaller emitting area of 4 assumed in Goicoechea et al (2012) and the estimating method, which is based on non-LTE analysis. The CO column density ratio of the hot and warm components in both studies is ∼20, indicating that the relative contribution of the two components remains invariable despite the different approaches.…”

Section: Position T 1 (K)mentioning

confidence: 99%

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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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Section: Excitation Conditionsmentioning

confidence: 62%

Section: Position T 1 (K)mentioning

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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“…Figure 8 presents the excitation diagram built from our best-fit model for CO. As extensively described in Goldsmith & Langer (1999), in local thermodynamical equilibrium conditions and under optically thin regime, the points in this type of diagram are expected to fall on a straight line, whose inverse of the slope is the excitation temperature of the transitions (also see the description of H 2 excitation diagrams in Sect. 4.1).…”

Section: Employing Shock Models: Energeticsmentioning

confidence: 90%

Impacts of pure shocks in the BHR71 bipolar outflow

Gusdorf

Riquelme

Anderl

et al. 2015

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Context. During the formation of a star, material is ejected along powerful jets that impact the ambient material. This outflow regulates star formation by e.g. inducing turbulence and heating the surrounding gas. Understanding the associated shocks is therefore essential to the study of star formation. Aims. We present comparisons of shock models with CO, H 2 , and SiO observations in a "pure" shock position in the BHR71 bipolar outflow. These comparisons provide an insight into the shock and pre-shock characteristics, and allow us to understand the energetic and chemical feedback of star formation on Galactic scales. Methods. New CO (J up = 16, 11, 7, 6, 4, 3) observations from the shocked regions with the SOFIA and APEX telescopes are presented and combined with earlier H 2 and SiO data (from the Spitzer and APEX telescopes). The integrated intensities are compared to a grid of models that were obtained from a magneto-hydrodynamical shock code, which calculates the dynamical and chemical structure of these regions combined with a radiative transfer module based on the "large velocity gradient" approximation. Results. The CO emission leads us to update the conclusions of our previous shock analysis: pre-shock densities of 10 4 cm −3 and shock velocities around 20−25 km s −1 are still constrained, but older ages are inferred (∼4000 years). Conclusions. We evaluate the contribution of shocks to the excitation of CO around forming stars. The SiO observations are compatible with a scenario where less than 4% of the pre-shock SiO belongs to the grain mantles. We infer outflow parameters: a mass of 1.8 × 10 −2 M was measured in our beam, in which a momentum of 0.4 M km s −1 is dissipated, corresponding to an energy of 4.2 × 10 43 erg. We analyse the energetics of the outflow species by species. Comparing our results with previous studies highlights their dependence on the method: H 2 observations only are not sufficient to evaluate the mass of outflows.

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“…The Heterodyne Instrument for Far-Infrared (HIFI; de Graauw et al 2010) on Herschel offers a unique opportunity to observe spectrally resolved high-J CO lines of various isotopologs with unprecendented sensitivity (see Yıldız et al 2010;Plume et al 2012, for early results). Even higher transitions of CO up to J u = 50 are now routinely observed with the Photoconducting Array and Spectrometer (PACS; Poglitsch et al 2010) and the Spectral and Photometric Imaging Receiver (SPIRE; Griffin et al 2010) instruments on Herschel, but those data are spectrally unresolved, detect mostly 12 CO, and probe primarily a hot shocked gas component associated with the source (e.g., van Kempen et al 2010;Herczeg et al 2012;Goicoechea et al 2012;Karska et al 2013;Manoj et al 2013;Green et al 2013). To study the bulk of the protostellar system and disentangle the various physical components, velocity resolved lines of isotopologs including optically thin C 18 O are needed.…”

Section: Introductionmentioning

confidence: 99%

High-JCO survey of low-mass protostars observed withHerschel-HIFI

Yıldız

Kristensen

Dishoeck

et al. 2013

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Context. In the deeply embedded stage of star formation, protostars start to heat and disperse their surrounding cloud cores. The evolution of these sources has traditionally been traced through dust continuum spectral energy distributions (SEDs), but the use of CO excitation as an evolutionary probe has not yet been explored due to the lack of high-J CO observations. Aims. The aim is to constrain the physical characteristics (excitation, kinematics, column density) of the warm gas in low-mass protostellar envelopes using spectrally resolved Herschel data of CO and compare those with the colder gas traced by lower excitation lines. Methods. Herschel-HIFI observations of high-J lines of 12 CO, 13 CO, and C 18 O (up to J u = 10, E u up to 300 K) are presented toward 26 deeply embedded low-mass Class 0 and Class I young stellar objects, obtained as part of the Water In Star-forming regions with Herschel (WISH) key program. This is the first large spectrally resolved high-J CO survey conducted for these types of sources. Complementary lower J CO maps were observed using ground-based telescopes, such as the JCMT and APEX and convolved to matching beam sizes. Results. The 12 CO 10-9 line is detected for all objects and can generally be decomposed into a narrow and a broad component owing to the quiescent envelope and entrained outflow material, respectively. The 12 CO excitation temperature increases with velocity from ∼60 K up to ∼130 K. The median excitation temperatures for 12 CO, 13 CO, and C 18 O derived from single-temperature fits to the J u = 2-10 integrated intensities are ∼70 K, 48 K and 37 K, respectively, with no significant difference between Class 0 and Class I sources and no trend with M env or L bol . Thus, in contrast to the continuum SEDs, the spectral line energy distributions (SLEDs) do not show any evolution during the embedded stage. In contrast, the integrated line intensities of all CO isotopologs show a clear decrease with evolutionary stage as the envelope is dispersed. Models of the collapse and evolution of protostellar envelopes reproduce the C 18 O results well, but underproduce the 13 CO and 12 CO excitation temperatures, due to lack of UV heating and outflow components in those models. The H 2 O 1 10 − 1 01 /CO 10-9 intensity ratio does not change significantly with velocity, in contrast to the H 2 O/CO 3-2 ratio, indicating that CO 10-9 is the lowest transition for which the line wings probe the same warm shocked gas as H 2 O. Modeling of the full suite of C 18 O lines indicates an abundance profile for Class 0 sources that is consistent with a freeze-out zone below 25 K and evaporation at higher temperatures, but with some fraction of the CO transformed into other species in the cold phase. In contrast, the observations for two Class I sources in Ophiuchus are consistent with a constant high CO abundance profile. Conclusions. The velocity resolved line profiles trace the evolution from the Class 0 to the Class I phase through decreasing line intensities, less prominent outflow...

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

Cited by 89 publications

References 60 publications

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

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

Impacts of pure shocks in the BHR71 bipolar outflow

High-JCO survey of low-mass protostars observed withHerschel-HIFI

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