Far infrared CO and H${}_2$O emission in intermediate-mass protostars

Abstract

Intermediate-mass young stellar objects (YSOs) provide a link to understand how feedback from shocks and UV radiation scales from low to high-mass star forming regions. Aims: Our aim is to analyze excitation of CO and H${}_2$O in deeply-embedded intermediate-mass YSOs and compare with low-mass and high-mass YSOs. Methods: Herschel/PACS spectral maps are analyzed for 6 YSOs with bolometric luminosities of $L_{\mathrm{bol}}\sim 10^2-10^3$ $L_{\odot }$. The maps cover spatial scales of $\sim 10^4$ AU in several CO and H${}_2$O lines located in the $\sim 55-210$ $\mu$m range. Results: Rotational diagrams of CO show two temperature components at $T_{\mathrm{rot}}\sim 320$ K and $T_{\mathrm{rot}}\sim 700-800$ K, comparable to low- and high-mass protostars probed at similar spatial scales. The diagrams for H${}_2$O show a single component at $T_{\mathrm{rot}}\sim 130$ K, as seen in low-mass protostars, and about $100$ K lower than in high-mass protostars. Since the uncertainties in $T_{\mathrm{rot}}$ are of the same order as the difference between the intermediate and high-mass protostars, we cannot conclude whether the change in rotational temperature occurs at a specific luminosity, or whether the change is more gradual from low- to high-mass YSOs. Conclusions: Molecular excitation in intermediate-mass protostars is comparable to the central $10^3$ AU of low-mass protostars and consistent within the uncertainties with the high-mass protostars probed at $3\cdot 10^3$ AU scales, suggesting similar shock conditions in all those sources.

arXiv commentAccepted to Astronomy & Astrophysics. 4 pages, 5 figures, 3 tables

References in corpus (22)

• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• Physical Conditions in Regions of Star Formation
• The Effects of Radiative Transfer on Low-Mass Star Formation
• Water in Star-Forming Regions with the Herschel Space Observatory (WISH): Overview of key program and first results
• Evolutionary Signatures in the Formation of Low-Mass Protostars. II. Towards Reconciling Models and Observations
• Evolutionary Signatures in the Formation of Low-Mass Protostars
• Embedded Protostars in the Dust, Ice, and Gas In Time (DIGIT) Key Program: Continuum SEDs, and an Inventory of Characteristic Far-Infrared Lines from PACS Spectroscopy
• Modelling Herschel observations of hot molecular gas emission from embedded low-mass protostars
• Origin of the hot gas in low-mass protostars: Herschel-PACS spectroscopy of HH 46
• Herschel/PACS Spectroscopic Survey of Protostars in Orion: The Origin of Far-Infrared CO Emission
• Water in star-forming regions with Herschel: highly excited molecular emission from the NGC 1333 IRAS 4B outflow
• High-J CO survey of low-mass protostars observed with Herschel-HIFI
• Water in star-forming regions with Herschel (WISH). IV. A survey of low-J H2O line profiles toward high-mass protostars
• Far-infrared molecular lines from Low- to High-Mass Star Forming Regions observed with Herschel
• Herschel Far-Infrared Spectral-mapping of Orion BN/KL Outflows: Spatial distribution of excited CO, H2O, OH, O and C+ in shocked gas
• Herschel-HIFI observations of high-J CO and isotopologues in star-forming regions: from low- to high-mass
• OH far-infrared emission from low- and intermediate-mass protostars surveyed with Herschel-PACS
• Shockingly low water abundances in Herschel / PACS observations of low-mass protostars in Perseus
• Observational evidence for dissociative shocks in the inner 100 AU of low-mass protostars using Herschel-HIFI
• Warm gas towards young stellar objects in Corona Australis - Herschel/PACS observations from the DIGIT key programme
• Herschel-PACS spectroscopy of the intermediate mass protostar NGC7129 FIRS 2
• The water abundance behind interstellar shocks: results from $Herschel$/PACS and $Spitzer$/IRS observations of H${}_2$O, CO, and H${}_2$

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• The Herschel-PACS legacy of low-mass protostars: Properties of warm and hot gas and its origin in far-UV illuminated shocks
• 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
• CO in Protostars (COPS): $Herschel$-SPIRE Spectroscopy of Embedded Protostars
• The importance of radiative pumping on the emission of the H_2O submillimeter lines in galaxies
• Velocity-resolved high-J CO emission from massive star-forming clumps
• Far-infrared line emission from the outer Galaxy cluster Gy 3-7 with SOFIA/FIFI-LS: Physical conditions and UV fields