The Evolution of Far-Infrared Co Emission From Protostars

Manoj, P.; Green, Joel D.; Megeath, S. Thomas; Evans, Neal J.; Stutz, Amelia M.; Tobin, John J.; Watson, D. M.; Fischer, William J.; Furlan, Elise; Henning, Thomas

doi:10.3847/0004-637x/831/1/69

Cited by 27 publications

(34 citation statements)

References 90 publications

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“…We found a strong linear relation between L CO and L bol , which can be expressed as log(L CO ) = (0.62 ± 0.14)log(L bol ) − 2.10 ± 0.13, (5) but no systematic offset of L CO distinguished by the T bol of the sources. The same scenario is also found for the HOPS and DIGIT programs (Manoj et al 2013(Manoj et al , 2016. We found that the classification of embedded protostars still remains uncertain with the addition of Herschel -SPIRE spectra.…”

Section: Sed Classificationsupporting

confidence: 80%

Co in Protostars (Cops): Herschel-Spire Spectroscopy of Embedded Protostars

Yang¹,

Green²,

Team³

2017

Proceedings of the 72nd International Symposium on Molecular Spectroscopy

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We present full spectral scans from 200-670 µm of 26 Class 0+I protostellar sources, obtained with Herschel -SPIRE, as part of the "COPS-SPIRE" Open Time program, complementary to the DIGIT and WISH Key programs. Based on our nearly continuous, line-free spectra from 200-670 µm, the calculated bolometric luminosities (L bol ) increase by 50% on average, and the bolometric temperatures (T bol ) decrease by 10% on average, in comparison with the measurements without Herschel. Fifteen protostars have the same Class using T bol and L bol /L smm . We identify rotational transitions of CO lines from J = 4 → 3 to J = 13 → 12, along with emission lines of 13 CO, HCO + , H 2 O, and [C I]. The ratios of 12 CO to 13 CO indicate that 12 CO emission remains optically thick for J up < 13. We fit up to four components of temperature from the rotational diagram with flexible break points to separate the components. The distribution of rotational temperatures shows a primary population around 100 K with a secondary population at ∼350 K. We quantify the correlations of each line pair found in our dataset, and find the strength of correlation of CO lines decreases as the difference between J-level between two CO lines increases. The multiple origins of CO emission previously revealed by velocity-resolved profiles are consistent with this smooth distribution if each physical component contributes to a wide range of CO lines with significant overlap in the CO ladder. We investigate the spatial extent of CO emission and find that the morphology is more centrally peaked and less bipolar at high-J lines. We find the CO emission observed with SPIRE related to outflows, which consists two components, the entrained gas and shocked gas, as revealed by our rotational diagram analysis as well as the studies with velocity-resolved CO emission.

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Section: Sed Classificationsupporting

confidence: 80%

Co in Protostars (Cops): Herschel-Spire Spectroscopy of Embedded Protostars

Yang¹,

Green²,

Team³

2017

Proceedings of the 72nd International Symposium on Molecular Spectroscopy

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“…The lack of an obvious outflow from HOPS-108 has implications for the interpretation of its far-infrared CO emission. HOPS-108 is among the strongest far-infrared CO emitters, significantly above the relationship found by Manoj et al (2016). Thus, HOPS-108 may not actually be responsible for generating the CO emission and instead it is dominated by the terminal shock from the nearby HOPS-370 outflow as suggested by González-García et al (2016b).…”

Section: Remaining Questionsmentioning

confidence: 81%

The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. I. Identifying and Characterizing the Protostellar Content of the OMC-2 FIR4 and OMC-2 FIR3 Regions

Tobin

Megeath

Hoff

et al. 2019

ApJ

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We present ALMA (0.87 mm) and VLA (9 mm) observations toward OMC2-FIR4 and OMC2-FIR3 within the Orion integral-shaped filament that are thought to be the nearest regions of intermediate mass star formation. We characterize the continuum sources within these regions on ∼40 AU (0. 1) scales and associated molecular line emission at a factor of ∼30 better resolution than previous observations at similar wavelengths. We identify six compact continuum sources within OMC2-FIR4, four in OMC2-FIR3, and one additional source just outside OMC2-FIR4. This continuum emission is tracing the inner envelope and/or disk emission on less than 100 AU scales. HOPS-108 is the only protostar in OMC2-FIR4 that exhibits emission from high-excitation transitions of complex organic molecules (e.g., methanol and other lines) coincident with the continuum emission. HOPS-370 in OMC2-FIR3 with L ∼ 360 L , also exhibits emission from high-excitation methanol and other lines. The methanol emission toward these two protostars is indicative of temperatures high enough to thermally evaporate methanol from icy dust grains; overall these protostars have characteristics similar to hot corinos. We do not identify a clear outflow from HOPS-108 in 12 CO, but find evidence of interaction between the

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“…Karska et al (2018) and Galametz et al (2019) for IRAS4A. Chini et al (1997) and Manoj et al (2016) for OMC3 MMS6. (b) Internal luminosity.…”

Section: Discussionmentioning

confidence: 99%

A statistical analysis of dust polarization properties in ALMA observations of Class 0 protostellar cores

Gouellec

Maury

Guillet

et al. 2020

A&A

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Context. Recent observational progress has challenged the dust grain-alignment theories used to explain the polarized dust emission routinely observed in star-forming cores. Aims. In an effort to improve our understanding of the dust grain alignment mechanism(s), we have gathered a dozen ALMA maps of (sub)millimeter-wavelength polarized dust emission from Class 0 protostars and carried out a comprehensive statistical analysis of dust polarization quantities. Methods. We analyze the statistical properties of the polarization fraction Pfrac and the dispersion of polarization position angles S. More specifically, we investigate the relationship between S and Pfrac as well as the evolution of the product S × Pfrac as a function of the column density of the gas in the protostellar envelopes. We compare the observed trends with those found in polarization observations of dust in the interstellar medium and in synthetic observations of non-ideal magneto-hydrodynamic (MHD) simulations of protostellar cores. Results. We find a significant S ∝ Pfrac−0.79 correlation in the polarized dust emission from protostellar envelopes seen with ALMA; the power-law index significantly differs from the one observed by Planck in star-forming clouds. The product S × Pfrac, which is sensitive to the dust grain alignment efficiency, is approximately constant across three orders of magnitude in envelope column density (from NH2 = 1022 cm−2 to NH2 = 1025 cm−2), with a mean value of 0.36−0.17+0.10. This suggests that the grain alignment mechanism producing the bulk of the polarized dust emission in star-forming cores may not systematically depend on the local conditions such as the local gas density. However, in the lowest-luminosity sources in our sample, we find a hint of less efficient dust grain alignment with increasing column density. Our observations and their comparison with synthetic observations of MHD models suggest that the total intensity versus the polarized dust are distributed at different intrinsic spatial scales, which can affect the statistics from the ALMA observations, for example, by producing artificially high Pfrac. Finally, synthetic observations of MHD models implementing radiative alignment torques (RATs) show that the statistical estimator S × Pfrac is sensitive to the strength of the radiation field in the core. Moreover, we find that the simulations with a uniform perfect alignment (PA) of dust grains yield, on average, much higher S × Pfrac values than those implementing RATs; the ALMA values lie among those predicted by PA, and they are significantly higher than the ones obtained with RATs, especially at large column densities. Conclusions. Ultimately, our results suggest that dust alignment mechanism(s) are efficient at producing dust polarized emission in the various local conditions typical of Class 0 protostars. The grain alignment efficiency found in these objects seems to be higher than the efficiency produced by the standard RAT alignment of paramagnetic grains. Further studies will be needed to understand how more efficient grain alignment via, for example, different irradiation conditions, dust grain characteristics, or additional grain alignment mechanisms can reproduce the observations.

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The Evolution of Far-Infrared Co Emission From Protostars

Cited by 27 publications

References 90 publications

Co in Protostars (Cops): Herschel-Spire Spectroscopy of Embedded Protostars

Co in Protostars (Cops): Herschel-Spire Spectroscopy of Embedded Protostars

The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. I. Identifying and Characterizing the Protostellar Content of the OMC-2 FIR4 and OMC-2 FIR3 Regions

A statistical analysis of dust polarization properties in ALMA observations of Class 0 protostellar cores

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