Sulphur and carbon isotopes towards Galactic centre clouds

Abstract

Measuring isotopic ratios is a sensitive technique used to obtain information on stellar nucleosynthesis and chemical evolution. We present measurements of the carbon and sulphur abundances in the interstellar medium of the central region of our Galaxy. The selected targets are the +50km/s Cloud and several l.o.s. clouds towards Sgr B2(N). Towards the +50km/s Cloud, we observed the J=2-1 rotational transitions of CS, C34S, 13CS, C33S, and 13C34S, and the J=3-2 transitions of CS and C34S with the IRAM-30m telescope, as well as the J=6-5 transitions of C34S and 13CS with the APEX 12m telescope, all in emission. The J=2-1 rotational transitions of CS, C34S, 13CS, and 13C34S were observed with ALMA in the envelope of Sgr B2(N), with those of CS and C34S also observed in the l.o.s. clouds towards Sgr B2(N), all in absorption. In the +50km/s Cloud we derive a 12C13C isotopic ratio of ~22.1, that leads, with the measured 13CS/C34S line intensity ratio, to a 32S/34S ratio of 16.3+3.0-2.4. We also derive the 32S/34S isotopic ratio more directly from the two isotopologues 13CS and 13C34S, which leads to an independent 32S/34S estimation of 16.3+2.1-1.7 and 17.9+-5.0 for the +50km/s Cloud and Sgr B2(N), respectively. We also obtain a 34S/33S ratio of ~4.3 in the +50 km/s Cloud. Previous studies observed a decreasing trend in the 32S/34S isotopic ratios when approaching the Galactic centre. Our result indicates a termination of this tendency at least at a galactocentric distance of 130-30+60 pc. This is at variance with findings based on 12C/13C, 14N/15N and 18O/17O isotope ratios, where the above-mentioned trend is observed to continue right to the central molecular zone. This can indicate a drop in the production of massive stars at the Galactic centre, in the same line as recent metallicity gradient studies, and opens the work towards a comparison with Galactic and stellar evolution models.

arXiv comment16 pages, 7 figures, accepted for publication by A&A

References in corpus (74)

• A computer program for fast non-LTE analysis of interstellar line spectra
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Galactic Chemical Evolution: Hydrogen Through Zinc
• The Cologne Database for Molecular Spectroscopy, CDMS, in the Virtual Atomic and Molecular Data Centre, VAMDC
• Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)
• How to Calculate Molecular Column Density
• The Evolution of Isotope Ratios in the Milky Way Galaxy
• Evaporation of ices near massive stars: models based on laboratory TPD data
• The Distribution Of Heavy Elements In Spiral And Elliptical Galaxies
• Chemistry of Dark Clouds: Databases, Networks, and Models
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• Reaction Networks For Interstellar Chemical Modelling: Improvements and Challenges
• A Trigonometric Parallax of Sgr B2
• The APOGEE red-clump catalog: Precise distances, velocities, and high-resolution elemental abundances over a large area of the Milky Way's disk
• Dense gas in the Galactic central molecular zone is warm and heated by turbulence
• NuGrid stellar data set I. Stellar yields from H to Bi for stars with metallicities Z = 0.02 and Z = 0.01
• The largest oxigen bearing organic molecule repository
• On the reservoir of sulphur in dark clouds : chemistry and elemental abundance reconciled
• On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk
• Modeling Sulfur Depletion in Interstellar Clouds
• Exploring Molecular Complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2)
• Weeds: a CLASS extension for the analysis of millimeter and sub-millimeter spectral surveys
• Re-exploring Molecular Complexity with ALMA (ReMoCA): Interstellar detection of urea
• The thermal state of molecular clouds in the Galactic Center: evidence for non-photon-driven heating
• The effect of uncertainties on chemical models of dark clouds
• Oxygen depletion in dense molecular clouds: a clue to a low O2 abundance?
• The physical and chemical structure of Sagittarius B2, I. Three-dimensional thermal dust and free-free continuum modeling on 100 au to 45 pc scales
• Isotopic fractionation of carbon, deuterium and nitrogen : a full chemical study
• Exploring molecular complexity with ALMA (EMoCA): Alkanethiols and alkanols in Sagittarius B2(N2)
• Sulphur chemistry in the L1544 pre-stellar core
• Dense gas in nearby galaxies XVI. The nuclear starburst environment in NGC4945
• Metallicity in the Galactic Center: The Quintuplet cluster
• Distributed star formation throughout the Galactic Center cloud Sgr B2
• The complex chemistry of hot cores in Sagittarius B2(N): Influence of cosmic-ray ionization and thermal history
• Exploring molecular complexity with ALMA (EMoCA): Detection of three new hot cores in Sagittarius B2(N)
• Comparative chemistry of diffuse clouds III: sulfur-bearing molecules
• On carbon and oxygen isotope ratios in starburst galaxies: New data from NGC253 and Mrk231 and their implications
• Galactic interstellar 18O/17O ratios - a radial gradient?
• Physical conditions in the central molecular zone inferred by H3+
• The physical and chemical structure of Sagittarius B2. II. Continuum millimeter emission of SgrB2(M) and SgrB2(N) with ALMA
• The chemical abundances in the Galactic Centre from the atmospheres of Red Supergiants
• Rotational spectroscopy of isotopic vinyl cyanide, H${}_2$C=CH$-$C$\equiv$N, in the laboratory and in space
• Detection of Widespread Hot Ammonia in the Galactic Center
• Probing isotopic ratios at z = 0.89: molecular line absorption in front of the quasar PKS 1830-211
• Comparisons of the radial distributions of core-collapse supernovae with those of young and old stellar populations
• Ionization fraction and the enhanced sulfur chemistry in Barnard 1
• A systematic TMRT observational study of Galactic ${}^{12}$C/${}^{13}$C ratios from Formaldehyde
• Interstellar gas within $\sim 10$ pc of Sgr A${}^{\ast }$
• Interstellar CN and CH+ in Diffuse Molecular Clouds: 12C/13C Ratios and CN Excitation
• A large 12C/13C isotopic ratio in M82 and NGC253
• The radial distribution of core-collapse supernovae in spiral host galaxies
• Extragalactic CS survey
• Large scale grain mantle disruption in the Galactic Center
• The Physical and chemical structure of Sagittarius B2 -- IV. Converging filaments in the high-mass cluster forming region Sgr B2(N)
• Molecular tracers of high mass star-formation in external galaxies
• The abundance of 36S in IRC+10216 and its production in the Galaxy
• Oxygen fractionation in dense molecular clouds
• The dynamical evolution of molecular clouds near the Galactic Centre -- III. Tidally--induced star formation in protocluster clouds
• 3 mm spectral line survey of two lines of sight toward two typical cloud complexes in the Galactic Center
• Oxygen isotopic ratios in galactic clouds along the line of sight towards Sagittarius B2
• First metallicity determination from Near-Infrared spectra for five obscured Cepheids discovered in the inner Disk
• Dense molecular cocoons in the massive protocluster W3 IRS5: a test case for models of massive star formation
• Ground-state ammonia and water in absorption towards Sgr B2
• VLT/UVES constraints on the carbon isotope ratio 12C/13C at z=1.15 toward the quasar HE 0515-4414
• The Molecular Chemistry of Diffuse and Translucent Clouds in the Line-of-Sight to Sgr B2
• Small-scale physical and chemical structure of diffuse and translucent molecular clouds along the line of sight to Sgr B2
• A sensitive 3 mm line survey of L483: a broad view of the chemical composition of a core around a Class 0 object
• Odin observations of the Galactic centre in the 118-GHz band. Upper limit to the O2 abundance
• Molecular Cloud Cores in the Galactic Center 50 $\mathrm{km}{\mathrm{s}}^{-1}$ Molecular Cloud
• Herschel HIFI Observations of the Sgr A +50 km/s Cloud. Deep Searches for O2 in Emission and Foreground Absorption
• Mapping CS in Starburst Galaxies: Disentangling and Characterising Dense Gas
• Astrochemistry in external galaxies: how to use molecules as probes of their physical conditions
• Rotational spectroscopy of isotopic species of methyl mercaptan at millimeter and submillimeter wavelengths: CH${}_3$${}^{34}$SH
• Gas physics and dynamics in the central 50 pc of the Galaxy

Cited by in corpus (17)

• ALCHEMI: an ALMA Comprehensive High-resolution Extragalactic Molecular Inventory. Survey presentation and first results from the ACA array
• Direct measurements of carbon and sulfur isotope ratios in the Milky Way
• The detection of a hot molecular core in the extreme outer Galaxy
• Sulphur-rich cold gas around the hot core precursor G328.2551-0.5321. An APEX unbiased spectral survey of the 2 mm, 1.2 mm, and 0.8 mm atmospheric windows
• The evolution of temperature and density structures of OB cluster-forming molecular clumps
• ALMA uncovers highly filamentary structure towards the Sgr E region
• The molecular environment of the solar-type protostar IRAS 16293-2422
• Living on the edge of the Central Molecular Zone: G1.3 is the more likely candidate for gas accretion into the CMZ
• Charting Circumstellar Chemistry of Carbon-rich AGB Stars: I. ALMA 3 mm spectral surveys
• Sulfur isotope ratios in the Large Magellanic Cloud
• The physical and chemical structure of Sagittarius B2, VIII. Full molecular line survey of hot cores
• An ALCHEMI inspection of sulphur-bearing species towards the central molecular zone of NGC 253
• Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri
• A Systematic Observational Study on Galactic Interstellar Ratio 18O/17O. II. C18O and C17O J=2-1 Data Analysis
• Complex Organic Molecules towards the central molecular zone of NGC 253
• CHIMPS2: ${}^{13}$CO $J=3\to 2$ emission in the Central Molecular Zone
• Identification of molecular line emission using Convolutional Neural Networks