The physical conditions in IRDC clumps from<i>Herschel</i>/HIFI observations of H<sub>2</sub>O

Shipman, R.; Tak, F. F. S. van der; Wyrowski, F.; Herpin, Fabrice; Frieswijk, W.

doi:10.1051/0004-6361/201423912

Cited by 12 publications

(16 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because we have no complementary 13 CO data, the global collapse scenario there is more tentative. However, single pointings in H 2 O in G11.11.-0.12 (Shipman et al 2014) already show infall signatures similar to G28.37+0.07, so that we conclude that global collapse could probably be a feature shared by all massive IRDCs that are embedded in GMCs. Higher angular resolution molecular line observations using, e.g.…”

Section: Collapse Signatures In Molecular Line Profilesmentioning

confidence: 64%

“…8. The same velocity of sources 2 and 6 are also derived by Shipman et al (2014) based on pointed observations of optically thin lines, such as N 2 H + and C 17 O, using Herschel and APEX.…”

Section: Collapse Signatures In Molecular Line Profilesmentioning

confidence: 86%

“…Local infall on the pre-and protostellar sources is seen in H 2 O observations (Shipman et al 2014) of source 2 and source 6 (labelled G28-MM and G28-NH 3 in Shipman et al 2014), where the water line appears in absorption and is systematically redshifted relative to the systemic velocity of the clump. However, comparing 12 CO and 13 CO spectra across the whole IRDC (the two off-source spectra in Figs.…”

Section: Collapse Signatures In Molecular Line Profilesmentioning

confidence: 99%

See 2 more Smart Citations

Understanding star formation in molecular clouds

Schneider

Csengeri

Klessen

et al. 2015

A&A

View full text Add to dashboard Cite

We analyse column density and temperature maps derived from Herschel dust continuum observations of a sample of prominent, massive infrared dark clouds (IRDCs) i.e. G11.11-0.12, G18.82-0.28, G28.37+0.07, and G28.53-0.25. We disentangle the velocity structure of the clouds using 13 CO 1→0 and 12 CO 3→2 data, showing that these IRDCs are the densest regions in massive giant molecular clouds (GMCs) and not isolated features. The probability distribution function (PDF) of column densities for all clouds have a power-law distribution over all (high) column densities, regardless of the evolutionary stage of the cloud: G11.11-0.12, G18.82-0.28, and G28.37+0.07 contain (proto)-stars, while G28.53-0.25 shows no signs of star formation. This is in contrast to the purely log-normal PDFs reported for near and/or mid-IR extinction maps. We only find a log-normal distribution for lower column densities, if we perform PDFs of the column density maps of the whole GMC in which the IRDCs are embedded. By comparing the PDF slope and the radial column density profile of three of our clouds, we attribute the power law to the effect of large-scale gravitational collapse and to local free-fall collapse of pre-and protostellar cores for the highest column densities. A significant impact on the cloud properties from radiative feedback is unlikely because the clouds are mostly devoid of star formation. Independent from the PDF analysis, we find infall signatures in the spectral profiles of 12 CO for G28.37+0.07 and G11.11-0.12, supporting the scenario of gravitational collapse. Our results are in line with earlier interpretations that see massive IRDCs as the densest regions within GMCs, which may be the progenitors of massive stars or clusters. At least some of the IRDCs are probably the same features as ridges (high column density regions with N > 10 23 cm −2 over small areas), which were defined for nearby IR-bright GMCs. Because IRDCs are only confined to the densest (gravity dominated) cloud regions, the PDF constructed from this kind of a clipped image does not represent the (turbulence dominated) low column density regime of the cloud.

show abstract

Section: Collapse Signatures In Molecular Line Profilesmentioning

confidence: 64%

Section: Collapse Signatures In Molecular Line Profilesmentioning

confidence: 86%

Section: Collapse Signatures In Molecular Line Profilesmentioning

confidence: 99%

See 1 more Smart Citation

Understanding star formation in molecular clouds

Schneider

Csengeri

Klessen

et al. 2015

A&A

View full text Add to dashboard Cite

show abstract

“…So far, no prestellar cores have been detected with such a large mass. Indeed, follow-up observations of many suggested high-mass starless core candidates revealed molecular outflows or maser emission, irrefutable signs of star formation (e.g., Bontemps et al 2010;Duarte-Cabral et al 2013;Tan et al 2013;Shipman et al 2014;Tan et al 2016;Feng et al 2016b).…”

Section: Uncertainties In the Determination Of Physical Parametersmentioning

confidence: 99%

A Massive Prestellar Clump Hosting No High-mass Cores

Sanhueza¹,

Jackson

Zhang

et al. 2017

ApJ

125

160

View full text Add to dashboard Cite

The Infrared Dark Cloud (IRDC) G028.23-00.19 hosts a massive (1,500 M ), cold (12 K), and 3.6-70 µm IR dark clump (MM1) that has the potential to form high-mass stars. We observed this prestellar clump candidate with the SMA (∼3. 5 resolution) and JVLA (∼2. 1 resolution) in order to characterize the early stages of high-mass star formation and to constrain theoretical models. Dust emission at 1.3 mm wavelength reveals 5 cores with masses ≤15 M . None of the cores currently have the mass reservoir to form a high-mass star in the prestellar phase. If the MM1 clump will ultimately form high-mass stars, its embedded cores must gather a significant amount of additional mass over time. No molecular outflows are detected in the CO (2-1) and SiO (5-4) transitions, suggesting that the SMA cores are starless. By using the NH 3 (1,1) line, the velocity dispersion of the gas is determined to be transonic or mildly supersonic (∆V nt /∆V th ∼1.1-1.8). The cores are not highly supersonic as some theories of high-mass star formation predict. The embedded cores are 4 to 7 times more massive than the clump thermal Jeans mass and the most massive core (SMA1) is 9 times less massive than the clump turbulent Jeans mass. These values indicate that neither thermal pressure nor turbulent pressure dominates the fragmentation of MM1. The low virial parameters of the cores (0.1-0.5) suggest that they are not in virial equilibrium, unless strong magnetic fields of ∼1-2 mG are present. We discuss high-mass star formation scenarios in a context based on IRDC G028.23-00.19, a study case believed to represent the initial fragmentation of molecular clouds that will form high-mass stars.

show abstract

“…In addition, four pre-stellar cores have been studied by Shipman et al (2014). The velocity profiles of the lowexcitation H 2 O lines toward this sample have been presented by van der Tak et al (2013), without detailed modeling.…”

Section: Introductionmentioning

confidence: 99%

Herschel-HIFI view of mid-IR quiet massive protostellar objects

Herpin

Chavarría

Jacq

et al. 2016

A&A

Self Cite

View full text Add to dashboard Cite

Aims. We present Herschel/HIFI observations of 14 water lines in a small sample of Galactic massive protostellar objects: NGC 6334I(N), DR21(OH), IRAS 16272-4837, and IRAS 05358+3543. Using water as a tracer of the structure and kinematics, we individually study each of these objects with the aim to estimate the amount of water around them, but to also to shed light on the high-mass star formation process. Methods. We analyzed the gas dynamics from the line profiles using Herschel-HIFI observations acquired as part of the WISH keyproject of 14 far-IR water lines (H 2 O) and several other species. Then through modeling the observations using the RATRAN radiative transfer code, we estimated outflow, infall, turbulent velocities, and molecular abundances and investigated the correlation with the evolutionary status of each source. Results. The four sources (and the previously studied W43-MM1) have been ordered in terms of evolution based on their spectral energy distribution from youngest to older: 1) NGC 64334I(N); 2) W43-MM1; 3) DR21(OH); 4) IRAS 16272-4837; 5) IRAS 05358+3543. The molecular line profiles exhibit a broad component coming from the shocks along the cavity walls that is associated with the protostars, and an infalling (or expanding, for IRAS 05358+3543) and passively heated envelope component, with highly supersonic turbulence that probably increases with the distance from the center. Accretion rates between 6.3 × 10 −5 and 5.6 × 10 −4 M yr −1 are derived from the infall observed in three of our sources. The outer water abundance is estimated to be at the typical value of a few 10 −8 , while the inner abundance varies from 1.7 × 10 −6 to 1.4 × 10 −4 with respect to H 2 depending on the source. Conclusions. We confirm that regions of massive star formation are highly turbulent and that the turbulence probably increases in the envelope with the distance to the star. The inner abundances are lower than the expected, 10 −4 , perhaps because our observed lines do not probe deep enough into the inner envelope or because photodissociation through protostellar UV photons is more efficient than expected. We show that the higher the infall or expansion velocity in the protostellar envelope, the higher the inner abundance. This may indicate that higher infall or expansion velocities generate shocks that will sputter water from the ice mantles of dust grains in the inner region. High-velocity water must be formed in the gas phase from shocked material.

show abstract

The physical conditions in IRDC clumps fromHerschel/HIFI observations of H₂O

Cited by 12 publications

References 52 publications

Understanding star formation in molecular clouds

Understanding star formation in molecular clouds

A Massive Prestellar Clump Hosting No High-mass Cores

Herschel-HIFI view of mid-IR quiet massive protostellar objects

Contact Info

Product

Resources

About

The physical conditions in IRDC clumps fromHerschel/HIFI observations of H2O

Cited by 12 publications

References 52 publications

Understanding star formation in molecular clouds

Understanding star formation in molecular clouds

A Massive Prestellar Clump Hosting No High-mass Cores

Herschel-HIFI view of mid-IR quiet massive protostellar objects

Contact Info

Product

Resources

About

The physical conditions in IRDC clumps fromHerschel/HIFI observations of H₂O