The Herschel-PACS Legacy of Low-mass Protostars: The Properties of Warm and Hot Gas Components and Their Origin in Far-UV Illuminated Shocks

Karska, A.; Kaufman, Michael J.; Kristensen, L. E.; Dishoeck, E. F. van; Herczeg, Gregory J.; Mottram, J. C.; Tychoniec, Łukasz; Lindberg, Johan E.; Evans, Neal J.; Green, Joel D.; Yang, Yao-Lun; Gusdorf, A.; Itrich, Dominika; Siódmiak, N.

doi:10.3847/1538-4365/aaaec5

Cited by 68 publications

(131 citation statements)

References 102 publications

(234 reference statements)

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“…Nisini et al (2007) showed, based on SiO observations for a broader range of E up , that the conditions in the outflow may exhibit much higher kinetic temperatures. Their work showed an increase in temperature (up to 500 K) and density (up to 10 6 cm −3 ) for the high-velocity jet, consistent with the values derived from CO Herschel data (Karska et al 2018). For SiO, H 2 CO, and HCN we ran RADEX (van der Tak et al 2007) calculations to constrain excitation temperatures under the conditions expected in the protostellar outflow (n H2 = 10 4 -10 6 cm −3 ; T kin = 75 -700 K; ∆ = 10 km s −1 ).…”

Section: Analysis Methodssupporting

confidence: 81%

Chemical and kinematic structure of extremely high-velocity molecular jets in the Serpens Main star-forming region

Tychoniec

Hull

Kristensen

et al. 2019

A&A

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Context. Outflows are one of the first signposts of ongoing star formation. The fastest molecular component to the protostellar outflows -extremely high-velocity (EHV) molecular jets -are still puzzling since they are seen only rarely. As they originate deep inside the embedded protostar-disk system, they provide vital information about the outflow-launching process in the earliest stages. Aims. The first aim is to analyze the interaction between the EHV jet and the slow outflow by comparing their outflow force content. The second aim is to analyze the chemical composition of the different outflow velocity components and to reveal the spatial location of molecules. Methods. ALMA 3 mm (Band 3) and 1.3 mm (Band 6) observations of five outflow sources at 0 . 3 -0 . 6 (130 -260 au) resolution in the Serpens Main cloud are presented. Observations of CO, SiO, H 2 CO and HCN reveal the kinematic and chemical structure of those flows. Three velocity components are distinguished: the slow and the fast wing, and the EHV jet. Results. Out of five sources, three have the EHV component. Comparison of outflow forces reveals that only the EHV jet in the youngest source Ser-emb 8 (N) has enough momentum to power the slow outflow. The SiO abundance is generally enhanced with velocity, while HCN is present in the slow and the fast wing, but disappears in the EHV jet. For Ser-emb 8 (N), HCN and SiO show a bow-shock shaped structure surrounding one of the EHV peaks suggesting sideways ejection creating secondary shocks upon interaction with the surroundings. Also, the SiO abundance in the EHV gas decreases with distance from this protostar, whereas that in the fast wing increases. H 2 CO is mostly associated with low-velocity gas but also appears surprisingly in one of the bullets in the Ser-emb 8 (N) EHV jet. No complex organic molecules are found to be associated with the outflows. Conclusions. The high detection rate suggests that the presence of the EHV jet may be more common than previously expected. The EHV jet alone does not contain enough outflow force to explain the entirety of the outflowing gas. The origin and temporal evolution of the abundances of SiO, HCN and H 2 CO through high-temperature chemistry are discussed. The data are consistent with a low C/O ratio in the EHV gas versus high C/O ratio in the fast and slow wings.

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Section: Analysis Methodssupporting

confidence: 81%

Chemical and kinematic structure of extremely high-velocity molecular jets in the Serpens Main star-forming region

Tychoniec

Hull

Kristensen

et al. 2019

A&A

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“…Referring to the Karska et al (2014) study of Galactic massive YSOs, while most sources show some OH emission, the OH doublets at 84 µm and 79 µm are seen mostly in absorption for most sources. This is in contrast with low-and intermediate-mass YSOs, for which these OH doublets are seen mostly in emission, e.g., 63% sources show the 84 µm doublet in emission (Karska et al 2018). Based on the samples described in Wampfler et al (2013), the typical flux ratios are F(79.11)/F(79.18) ∼ 1.0 (range 0.6 − 1.8) and F(84.42)/F(84.60) ∼ 1.34 (range 0.8 − 2.9) for the doublet components, F(79.18)/F(84.42) ∼ 0.7 (range 0.3 − 0.86), and F(79)/F(84) ∼ 0.77 (range 0.4 − 1.23).…”

Section: Oh Linesmentioning

confidence: 69%

“…There is no correlation between H 2 O emission at 179 µm and [O i] or [C ii] emission, supporting an origin in distinct gas components (see also Karska et al 2018). Since H 2 O emission is thought to originate from the warm and hot components (T > ∼ 300 K) of the outflow system in young stars (see discussion in Sect.…”

Section: Line Flux Correlationsmentioning

confidence: 80%

“…All sources exhibit H 2 O emission; 55% of the sources show emission at either 179.5 or 108 µm (see also Karska et al 2013;Mottram et al 2017). The 179.5 µm line accounts for ∼ 8% of the total H 2 O luminosity 9 with a large scatter (Karska et al 2013(Karska et al , 2018. Typically the ratio of 179.5 µm to 108 µm emission is ∼ 0.9 (range 0.6 − 1.3, Karska et al 2013), therefore both lines together account for ∼ 18% of the total H 2 O line luminosity.…”

Section: H 2 O Linesmentioning

confidence: 99%

“…More recently, Karska et al (2018) analysed a large sample of low-luminosity Galactic YSOs. All sources exhibit H 2 O emission; 55% of the sources show emission at either 179.5 or 108 µm (see also Karska et al 2013;Mottram et al 2017).…”

Section: H 2 O Linesmentioning

confidence: 99%

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Herschel spectroscopy of massive young stellar objects in the Magellanic Clouds

Oliveira

Loon

Sewiło

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present Herschel Space Observatory Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver Fourier Transform Spectrometer (SPIRE FTS) spectroscopy of a sample of twenty massive Young Stellar Objects (YSOs) in the Large and Small Magellanic Clouds (LMC and SMC). We analyse the brightest farinfrared (far-IR) emission lines, that diagnose the conditions of the heated gas in the YSO envelope and pinpoint their physical origin. We compare the properties of massive Magellanic and Galactic YSOs. We find that [O i] and [C ii] emission, that originates from the photodissociation region associated with the YSOs, is enhanced with respect to the dust continuum in the Magellanic sample. Furthermore the photoelectric heating efficiency is systematically higher for Magellanic YSOs, consistent with reduced grain charge in low metallicity environments. The observed CO emission is likely due to multiple shock components. The gas temperatures, derived from the analysis of CO rotational diagrams, are similar to Galactic estimates. This suggests a common origin to the observed CO excitation, from low-luminosity to massive YSOs, both in the Galaxy and the Magellanic Clouds. Bright far-IR line emission provides a mechanism to cool the YSO environment. We find that, even though [O i], CO and [C ii] are the main line coolants, there is an indication that CO becomes less important at low metallicity, especially for the SMC sources. This is consistent with a reduction in CO abundance in environments where the dust is warmer due to reduced ultraviolet-shielding. Weak H 2 O and OH emission is detected, consistent with a modest role in the energy balance of wider massive YSO environments.

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Shocks and UV radiation around low-mass protostars: the Herschel-PACS legacy

Karska

Kaufman²,

Kristensen³

et al. 2017

Proc. IAU

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Far-infrared spectroscopy reveals gas cooling and its underlying heating due to physical processes taking place in the surroundings of protostars. These processes are reflected in both the chemistry and excitation of abundant molecular species. Here, we present the Herschel -PACS far-IR spectroscopy of 90 embedded low-mass protostars from the WISH (van Dishoeck et al. 2011), DIGIT (Green et al. 2013), and WILL surveys (Mottram et al. 2017). The 5 × 5 spectra covering the ∼ 50 ′′ × 50 ′′ field-of-view include rotational transitions of CO, H2O, and OH lines, as well as fine-structure [O I] and [C II] in the ∼50-200 µm range. The CO rotational temperatures (for Ju 14) are typically ∼300 K, with some sources showing additional components with temperatures as high as ∼1000 K. The H2O / CO and H2O / OH flux ratios are low compared to stationary shock models, suggesting that UV photons may dissociate some H2O and decrease its abundance. Comparison to C shock models illuminated by UV photons shows good agreement between the line emission and the models for pre-shock densities of 10 5 cm −3 and UV fields 0.1-10 times the interstellar value. The far-infrared molecular and atomic lines are the unique diagnostic of shocks and UV fields in deeply-embedded sources.

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The Herschel-PACS Legacy of Low-mass Protostars: The Properties of Warm and Hot Gas Components and Their Origin in Far-UV Illuminated Shocks

Cited by 68 publications

References 102 publications

Chemical and kinematic structure of extremely high-velocity molecular jets in the Serpens Main star-forming region

Chemical and kinematic structure of extremely high-velocity molecular jets in the Serpens Main star-forming region

Herschel spectroscopy of massive young stellar objects in the Magellanic Clouds

Shocks and UV radiation around low-mass protostars: the Herschel-PACS legacy

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