Report
View in EDS

Origin of warm and hot gas emission from low-mass protostars: Herschel-HIFI observations of CO J=16-15. I. Line profiles, physical conditions, and H2O abundance

Bibliographic Details
Title: Origin of warm and hot gas emission from low-mass protostars: Herschel-HIFI observations of CO J=16-15. I. Line profiles, physical conditions, and H2O abundance
Authors: Kristensen, L. E., van Dishoeck, E. F., Mottram, J. C., Karska, A., Yildiz, U. A., Bergin, E. A., Bjerkeli, P., Cabrit, S., Doty, S., Evans II, N. J., Gusdorf, A., Harsono, D., Herczeg, G. J., Johnstone, D., Jørgensen, J. K., van Kempen, T. A., Lee, J. -E., Maret, S., Tafalla, M., Visser, R., Wampfler, S. F.
Source: A&A 605, A93 (2017)
Publication Year: 2017
Collection: Astrophysics
Subject Terms: Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics
More Details: (Abridged) Through spectrally unresolved observations of high-J CO transitions, Herschel-PACS has revealed large reservoirs of warm (300 K) and hot (700 K) molecular gas around low-mass protostars. We aim to shed light on the excitation and origin of the CO ladder observed toward protostars, and on the water abundance in different physical components using spectrally resolved Herschel-HIFI data. Observations are presented of the highly excited CO line J=16-15 with Herschel-HIFI toward 24 low-mass protostellar objects. The spectrally resolved profiles show two distinct velocity components: a broad component with an average FWHM of 20 km/s, and a narrower component with a FWHM of 5 km/s that is often offset from the source velocity. The average rotational temperature over the entire profile, as measured from comparison between CO J=16-15 and 10-9 emission, is ~300 K. A radiative-transfer analysis shows that the average H2O/CO column-density ratio is ~0.02, suggesting a total H2O abundance of ~2x10^-6. Two distinct velocity profiles observed in the HIFI line profiles suggest that the CO ladder observed with PACS consists of two excitation components. The warm component (300 K) is associated with the broad HIFI component, and the hot component (700 K) is associated with the offset HIFI component. The former originates in either outflow cavity shocks or the disk wind, and the latter in irradiated shocks. The ubiquity of the warm and hot CO components suggests that fundamental mechanisms govern the excitation of these components; we hypothesize that the warm component arises when H2 stops being the dominant coolant. In this scenario, the hot component arises in cooling molecular H2-poor gas just prior to the onset of H2 formation. High spectral resolution observations of highly excited CO transitions uniquely shed light on the origin of warm and hot gas in low-mass protostellar objects.
Comment: Accepted for publication in A&A
Document Type: Working Paper
DOI: 10.1051/0004-6361/201630127
Access URL: http://arxiv.org/abs/1705.10269
Accession Number: edsarx.1705.10269
Database: arXiv
FullText Text:
  Availability: 0
CustomLinks:
  – Url: http://arxiv.org/abs/1705.10269
    Name: EDS - Arxiv
    Category: fullText
    Text: View this record from Arxiv
    MouseOverText: View this record from Arxiv
  – Url: https://resolver.ebsco.com/c/xy5jbn/result?sid=EBSCO:edsarx&genre=article&issn=&ISBN=&volume=&issue=&date=20170529&spage=&pages=&title=Origin of warm and hot gas emission from low-mass protostars: Herschel-HIFI observations of CO J=16-15. I. Line profiles, physical conditions, and H2O abundance&atitle=Origin%20of%20warm%20and%20hot%20gas%20emission%20from%20low-mass%20protostars%3A%20Herschel-HIFI%20observations%20of%20CO%20J%3D16-15.%20I.%20Line%20profiles%2C%20physical%20conditions%2C%20and%20H2O%20abundance&aulast=Kristensen%2C%20L.%20E.&id=DOI:10.1051/0004-6361/201630127
    Name: Full Text Finder (for New FTF UI) (s8985755)
    Category: fullText
    Text: Find It @ SCU Libraries
    MouseOverText: Find It @ SCU Libraries
Header DbId: edsarx
DbLabel: arXiv
An: edsarx.1705.10269
RelevancyScore: 961
AccessLevel: 3
PubType: Report
PubTypeId: report
PreciseRelevancyScore: 961.163635253906
IllustrationInfo
Items – Name: Title
  Label: Title
  Group: Ti
  Data: Origin of warm and hot gas emission from low-mass protostars: Herschel-HIFI observations of CO J=16-15. I. Line profiles, physical conditions, and H2O abundance
– Name: Author
  Label: Authors
  Group: Au
  Data: <searchLink fieldCode="AR" term="%22Kristensen%2C+L%2E+E%2E%22">Kristensen, L. E.</searchLink><br /><searchLink fieldCode="AR" term="%22van+Dishoeck%2C+E%2E+F%2E%22">van Dishoeck, E. F.</searchLink><br /><searchLink fieldCode="AR" term="%22Mottram%2C+J%2E+C%2E%22">Mottram, J. C.</searchLink><br /><searchLink fieldCode="AR" term="%22Karska%2C+A%2E%22">Karska, A.</searchLink><br /><searchLink fieldCode="AR" term="%22Yildiz%2C+U%2E+A%2E%22">Yildiz, U. A.</searchLink><br /><searchLink fieldCode="AR" term="%22Bergin%2C+E%2E+A%2E%22">Bergin, E. A.</searchLink><br /><searchLink fieldCode="AR" term="%22Bjerkeli%2C+P%2E%22">Bjerkeli, P.</searchLink><br /><searchLink fieldCode="AR" term="%22Cabrit%2C+S%2E%22">Cabrit, S.</searchLink><br /><searchLink fieldCode="AR" term="%22Doty%2C+S%2E%22">Doty, S.</searchLink><br /><searchLink fieldCode="AR" term="%22Evans+II%2C+N%2E+J%2E%22">Evans II, N. J.</searchLink><br /><searchLink fieldCode="AR" term="%22Gusdorf%2C+A%2E%22">Gusdorf, A.</searchLink><br /><searchLink fieldCode="AR" term="%22Harsono%2C+D%2E%22">Harsono, D.</searchLink><br /><searchLink fieldCode="AR" term="%22Herczeg%2C+G%2E+J%2E%22">Herczeg, G. J.</searchLink><br /><searchLink fieldCode="AR" term="%22Johnstone%2C+D%2E%22">Johnstone, D.</searchLink><br /><searchLink fieldCode="AR" term="%22Jørgensen%2C+J%2E+K%2E%22">Jørgensen, J. K.</searchLink><br /><searchLink fieldCode="AR" term="%22van+Kempen%2C+T%2E+A%2E%22">van Kempen, T. A.</searchLink><br /><searchLink fieldCode="AR" term="%22Lee%2C+J%2E+-E%2E%22">Lee, J. -E.</searchLink><br /><searchLink fieldCode="AR" term="%22Maret%2C+S%2E%22">Maret, S.</searchLink><br /><searchLink fieldCode="AR" term="%22Tafalla%2C+M%2E%22">Tafalla, M.</searchLink><br /><searchLink fieldCode="AR" term="%22Visser%2C+R%2E%22">Visser, R.</searchLink><br /><searchLink fieldCode="AR" term="%22Wampfler%2C+S%2E+F%2E%22">Wampfler, S. F.</searchLink>
– Name: TitleSource
  Label: Source
  Group: Src
  Data: A&A 605, A93 (2017)
– Name: DatePubCY
  Label: Publication Year
  Group: Date
  Data: 2017
– Name: Subset
  Label: Collection
  Group: HoldingsInfo
  Data: Astrophysics
– Name: Subject
  Label: Subject Terms
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22Astrophysics+-+Astrophysics+of+Galaxies%22">Astrophysics - Astrophysics of Galaxies</searchLink><br /><searchLink fieldCode="DE" term="%22Astrophysics+-+Solar+and+Stellar+Astrophysics%22">Astrophysics - Solar and Stellar Astrophysics</searchLink>
– Name: Abstract
  Label: Description
  Group: Ab
  Data: (Abridged) Through spectrally unresolved observations of high-J CO transitions, Herschel-PACS has revealed large reservoirs of warm (300 K) and hot (700 K) molecular gas around low-mass protostars. We aim to shed light on the excitation and origin of the CO ladder observed toward protostars, and on the water abundance in different physical components using spectrally resolved Herschel-HIFI data. Observations are presented of the highly excited CO line J=16-15 with Herschel-HIFI toward 24 low-mass protostellar objects. The spectrally resolved profiles show two distinct velocity components: a broad component with an average FWHM of 20 km/s, and a narrower component with a FWHM of 5 km/s that is often offset from the source velocity. The average rotational temperature over the entire profile, as measured from comparison between CO J=16-15 and 10-9 emission, is ~300 K. A radiative-transfer analysis shows that the average H2O/CO column-density ratio is ~0.02, suggesting a total H2O abundance of ~2x10^-6. Two distinct velocity profiles observed in the HIFI line profiles suggest that the CO ladder observed with PACS consists of two excitation components. The warm component (300 K) is associated with the broad HIFI component, and the hot component (700 K) is associated with the offset HIFI component. The former originates in either outflow cavity shocks or the disk wind, and the latter in irradiated shocks. The ubiquity of the warm and hot CO components suggests that fundamental mechanisms govern the excitation of these components; we hypothesize that the warm component arises when H2 stops being the dominant coolant. In this scenario, the hot component arises in cooling molecular H2-poor gas just prior to the onset of H2 formation. High spectral resolution observations of highly excited CO transitions uniquely shed light on the origin of warm and hot gas in low-mass protostellar objects.<br />Comment: Accepted for publication in A&A
– Name: TypeDocument
  Label: Document Type
  Group: TypDoc
  Data: Working Paper
– Name: DOI
  Label: DOI
  Group: ID
  Data: 10.1051/0004-6361/201630127
– Name: URL
  Label: Access URL
  Group: URL
  Data: <link linkTarget="URL" linkTerm="http://arxiv.org/abs/1705.10269" linkWindow="_blank">http://arxiv.org/abs/1705.10269</link>
– Name: AN
  Label: Accession Number
  Group: ID
  Data: edsarx.1705.10269
PLink https://login.libproxy.scu.edu/login?url=https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&scope=site&db=edsarx&AN=edsarx.1705.10269
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1051/0004-6361/201630127
    Subjects:
      – SubjectFull: Astrophysics - Astrophysics of Galaxies
        Type: general
      – SubjectFull: Astrophysics - Solar and Stellar Astrophysics
        Type: general
    Titles:
      – TitleFull: Origin of warm and hot gas emission from low-mass protostars: Herschel-HIFI observations of CO J=16-15. I. Line profiles, physical conditions, and H2O abundance
        Type: main
  BibRelationships:
    HasContributorRelationships:
      – PersonEntity:
          Name:
            NameFull: Kristensen, L. E.
      – PersonEntity:
          Name:
            NameFull: van Dishoeck, E. F.
      – PersonEntity:
          Name:
            NameFull: Mottram, J. C.
      – PersonEntity:
          Name:
            NameFull: Karska, A.
      – PersonEntity:
          Name:
            NameFull: Yildiz, U. A.
      – PersonEntity:
          Name:
            NameFull: Bergin, E. A.
      – PersonEntity:
          Name:
            NameFull: Bjerkeli, P.
      – PersonEntity:
          Name:
            NameFull: Cabrit, S.
      – PersonEntity:
          Name:
            NameFull: Doty, S.
      – PersonEntity:
          Name:
            NameFull: Evans II, N. J.
      – PersonEntity:
          Name:
            NameFull: Gusdorf, A.
      – PersonEntity:
          Name:
            NameFull: Harsono, D.
      – PersonEntity:
          Name:
            NameFull: Herczeg, G. J.
      – PersonEntity:
          Name:
            NameFull: Johnstone, D.
      – PersonEntity:
          Name:
            NameFull: Jørgensen, J. K.
      – PersonEntity:
          Name:
            NameFull: van Kempen, T. A.
      – PersonEntity:
          Name:
            NameFull: Lee, J. -E.
      – PersonEntity:
          Name:
            NameFull: Maret, S.
      – PersonEntity:
          Name:
            NameFull: Tafalla, M.
      – PersonEntity:
          Name:
            NameFull: Visser, R.
      – PersonEntity:
          Name:
            NameFull: Wampfler, S. F.
    IsPartOfRelationships:
      – BibEntity:
          Dates:
            – D: 29
              M: 05
              Type: published
              Y: 2017
ResultId 1