Deuteration around the ultracompact HII region Mon R2

Abstract

The massive star-forming region Mon R2 hosts the closest ultra-compact HII region that can be spatially resolved with current single-dish telescopes. We used the IRAM-30m telescope to carry out an unbiased spectral survey toward two important positions (namely IF and MP2), in order to studying the chemistry of deuterated molecules toward Mon R2. We found a rich chemistry of deuterated species at both positions, with detections of C2D, DCN, DNC, DCO+, D2CO, HDCO, NH2D, and N2D+ and their corresponding hydrogenated species and isotopologs. Our high spectral resolution observations allowed us to resolve three velocity components: the component at 10 km/s is detected at both positions and seems associated with the layer most exposed to the UV radiation from IRS 1; the component at 12 km/s is found toward the IF position and seems related to the molecular gas; finally, a component at 8.5 km/s is only detected toward the MP2 position, most likely related to a low-UV irradiated PDR. We derived the column density of all the species, and determined the deuterium fractions (Dfrac). The values of Dfrac are around 0.01 for all the observed species, except for HCO+ and N2H+ which have values 10 times lower. The values found in Mon R2 are well explained with pseudo-time-dependent gas-phase model in which deuteration occurs mainly via ion-molecule reactions with H2D+, CH2D+ and C2HD+. Finally, the [H13CN]/[HN13C] ratio is very high (~11) for the 10 km/s component, which also agree with our model predictions for an age of ~0.01-0.1 Myr. The deuterium chemistry is a good tool for studying star-forming regions. The low-mass star-forming regions seem well characterized with Dfrac(N2H+) or Dfrac(HCO+), but it is required a complete chemical modeling to date massive star-forming regions, because the higher gas temperature together with the rapid evolution of massive protostars.

arXiv comment14 pages of manuscript, 17 pages of apendix, 7 figures in the main text, accepted for publication in A&A

References in corpus (35)

• Probing the evolutionary status of starless cores through N2H+ and N2D+ observations
• What is the Total Deuterium Abundance in the Local Galactic Disk?
• First detection of triply-deuterated methanol
• High-resolution wide-band Fast Fourier Transform spectrometers
• Are PAHs precursors of small hydrocarbons in Photo--Dissociation Regions? The Horsehead case
• Detection of doubly-deuterated methanol in the solar-type protostar IRAS16293-2422
• Abundant H2D+ in the pre-stellar core L1544
• Testing grain surface chemistry : a survey of deuterated formaldehyde and methanol in low-mass Class 0 protostars
• Survey of ortho-H2D+(1_{1,0}-1_{1,1}) in dense cloud cores
• The N2D+/N2H+ ratio as an evolutionary tracer of Class 0 protostars
• Interstellar deuterated ammonia: From NH3 to ND3
• Deuteration as an evolutionary tracer in massive-star formation
• Nitrogen isotopic ratios in Barnard 1: a consistent study of the N2H+, NH3, CN, HCN and HNC isotopologues
• H-D Substitution in Interstellar Solid Methanol: A Key Route for D Enrichment
• Ortho-H2 and the Age of Interstellar Dark Clouds
• Nitrogen hydrides and the H2 ortho-to-para ratio in dark clouds
• Deuterated Thioformaldehyde in the Barnard 1 Cloud
• Deuterium chemistry in the Orion Bar PDR - "warm" chemistry starring CH2D+
• H2CO in the Horsehead PDR: Photo-desorption of dust grain ice mantles
• Deuterated molecules in DM Tau: DCO+, but no HDO
• Deuterium fractionation on interstellar grains studied with the direct master equation approach
• APEX 1 mm line survey of the Orion Bar
• Spectral line survey of the ultracompact HII region Mon R2
• CH2D+, the Search for the Holy Grail
• Deuterium fractionation in the Horsehead edge
• Mid-infrared PAH and H2 emission as a probe of physical conditions in extreme PDRs
• Deuterium fractionation and the degree of ionisation in massive clumps within infrared dark clouds
• Spatial distribution of small hydrocarbons in the neighborhood of the Ultra Compact HII region Monoceros R2
• Detection of a hot core in the intermediate-mass (IM) Class 0 protostar NGC 7129--FIRS2
• Detection of reactive ions in the ultracompact HII regions Mon R2 and G29.96-0.02
• Low temperature rate constants for the N(4S) + CH(X2Πr) reaction. Implications for N2 formation cycles in dense interstellar clouds
• Herschel / HIFI observations of CO, H2O and NH3 in Mon R2
• The distribution of ND2H in LDN1689N
• A deep search for molecular gas in two massive Lyman break galaxies at z=3 and 4: vanishing CO-emission due to low metallicity?
• Review of important reactions for the nitrogen chemistry in the interstellar medium

Cited by in corpus (22)

• Dynamics of cluster-forming hub-filament systems: The case of the high-mass star-forming complex Monoceros R2
• STATCONT: A statistical continuum level determination method for line-rich sources
• Complex organic molecules in strongly UV-irradiated gas
• Abundances of sulphur molecules in the Horsehead nebula. First NS+ detection in a photodissociation region
• [CII] 158 μm self-absorption and optical depth effects
• Kinetic temperature of massive star forming molecular clumps measured with formaldehyde
• Non-thermal emission from cosmic rays accelerated in HII regions
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde. III. The Orion Molecular Cloud 1
• Far-infrared observations of a massive cluster forming in the Monoceros R2 filament hub
• Kinetic temperature of massive star forming molecular clumps measured with formaldehyde. II. The Large Magellanic Cloud
• From forced collapse to H ii region expansion in Mon R2: Envelope density structure and age determination with Herschel
• The first CO+ image: Probing the HI/H2 layer around the ultracompact HII region Mon R2
• Gas phase Elemental abundances in Molecular cloudS (GEMS) VI. A sulphur journey across star-forming regions: study of thioformaldehyde emission
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde IV. The ALMA view of N113 and N159W in the LMC
• Probing the massive star forming environment - a multiwavelength investigation of the filamentary IRDC G333.73+0.37
• Probing the kinematics and chemistry of the hot core Mon R 2 IRS 3 using ALMA observations
• Gas vs. solid phase deuterated chemistry: HDCO and D${}_2$CO in massive star-forming regions
• Non-thermal emission from massive star forming regions: A possible SNR candidate G351.7-1.2?
• Chemical modeling of internal photon-dominated regions surrounding deeply embedded HC/UCHII regions
• The [OI] fine structure line profiles in Mon R2 and M17 SW: the puzzling nature of cold foreground material identified by [12CII] self-absorption
• Molecular deuterations in massive Starless Clump Candidates
• Singly- and doubly-deuterated formaldehyde in massive star-forming regions