The Molecular ISM in the Super Star Clusters of the Starburst NGC 253

Abstract

We present submillimeter spectra of the (proto-)super star cluster (SSC) candidates in the starbursting center of the nearby galaxy NGC 253 identified by Leroy et al. (2018). The 2.5pc resolution of our ALMA cycle 3 observations approach the size of the SSCs and allows the study of physical and chemical properties of the molecular gas in these sources. In the 14 SSC sources and in the frequency ranges 342.0-345.8 GHz and 353.9-357.7 GHz we detect 55 lines belonging to 19 different chemical species. The SSCs differ significantly in chemical complexity, with the richest clusters showing 19 species and the least complex showing 4 species. We detect HCN isotopologues and isomers (H${}^{13}$CN, HC${}^{15}$N, H${}^{15}$NC), abundant HC${}_3$N, SO and S${}^{18}$O, SO${}_2$, and H${}_2$CS. The gas ratios CO/HCN, CO/HCO${}^{+}$ are low, ~1-10, implying high dense gas fractions in the SSCs. Line ratio analyses suggests chemistry consistent with photon-dominated regions and mechanical heating. None of the SSCs near the galaxy center show line ratios that imply an X-ray dominated region, suggesting that heating by any (still unknown) AGN does not play a major role. The gas temperatures are high in most sources, with an average rotational temperature of ~130 K in SO${}_2$. The widespread existence of vibrationally excited HCN and HC${}_3$N transitions implies strong IR radiation fields, potentially trapped by a greenhouse effect due to high continuum opacities.

20 pages, 4 figures, 6 tables; accepted for publication in the Astrophysical Journal

References in corpus (32)

• Massive molecular outflows and negative feedback in ULIRGs observed by Herschel-PACS
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• Diagnostics of irradiated dense gas in galaxy nuclei. II. A grid of XDR and PDR models
• A multi-transition HCN and HCO+ study of 12 nearby active galaxies: AGN versus SB environments
• A 2 mm spectral line survey of the starburst galaxy NGC 253
• ALMA Reveals the Molecular Medium Fueling the Nearest Nuclear Starburst
• The anatomy of the Orion B Giant Molecular Cloud: A local template for studies of nearby galaxies
• Dense gas in luminous infrared galaxies
• Vibrationally Excited HCN in the Luminous Infrared Galaxy NGC 4418
• Molecular Line Emission as a Tool for Galaxy Observations (LEGO). I. HCN as a tracer of moderate gas densities in molecular clouds and galaxies
• Dense Molecular Gas Tracers in the Outflow of the Starburst Galaxy NGC 253
• The HNC/HCN Ratio in Star-Forming Regions
• Overluminous HNC Line Emission in Arp220, NGC4418 and Mrk231 - Global IR Pumping or XDRs?
• Lambda = 3 mm line survey of nearby active galaxies
• Mechanical feedback in the molecular ISM of luminous IR galaxies
• On carbon and oxygen isotope ratios in starburst galaxies: New data from NGC253 and Mrk231 and their implications
• Multi-molecule ALMA observations towards the Seyfert 1 galaxy NGC 1097
• Nobeyama Millimeter Interferometric HCN(1-0) and HCO+(1-0) Observations of Further Luminous Infrared Galaxies
• New insights on the dense molecular gas in NGC253 as traced by HCN and HCO+
• ALMA observations of 99 GHz free-free and H40$\alpha$ line emission from star formation in the centre of NGC 253
• Optical Depth Estimates and Effective Critical Densities of Dense Gas Tracers in the Inner Parts of Nearby Galaxy Discs
• Luminous HC3N line emission in NGC4418 - buried AGN or nascent starburst?
• Super Hot Cores in NGC 253: Witnessing the formation and early evolution of Super Star Clusters
• Survey of Water and Ammonia in Nearby galaxies (SWAN): Resolved Ammonia Thermometry, Water and Methanol Masers in the Nuclear Starburst of NGC 253
• The Greenhouse Effect in Buried Galactic Nuclei and the Resonant HCN Vibrational Emission
• Origins of Scatter in the Relationship Between HCN 1-0 and Dense Gas Mass in the Galactic Center
• Spatially resolved carbon and oxygen isotopic ratios in NGC 253 using optically thin tracers
• Diverse nuclear star-forming activities in the heart of NGC 253 resolved with ten-pc scale ALMA images
• VLA H53alpha and H92alpha line observations of the central region of NGC 253
• ALMA Multiple-Transition Molecular Line Observations of the Ultraluminous Infrared Galaxy IRAS 20551-4250: Different HCN, HCO+, HNC Excitation and Implications for Infrared Radiative Pumping
• A hidden molecular outflow in the LIRG Zw 049.057
• Nitrogen Fractionation in External Galaxies

Cited by in corpus (17)

• Photodissociation and X-Ray Dominated Regions
• ALCHEMI: an ALMA Comprehensive High-resolution Extragalactic Molecular Inventory. Survey presentation and first results from the ACA array
• CON-quest: Searching for the most obscured galaxy nuclei
• Tracing Interstellar Heating: An ALCHEMI Measurement of the HCN Isomers in NGC 253
• Outflows from Super Star Clusters in the Central Starburst of NGC253
• The Distribution and Origin of C${}_2$H in NGC 253 from ALCHEMI
• Starburst Energy Feedback Seen Through HCO${}^{+}$/HOC${}^{+}$ Emission in NGC 253 from ALCHEMI
• The Morpho-Kinematic Architecture of Super Star Clusters in the Center of NGC253
• PDFchem: A new fast method to determine ISM properties and infer environmental parameters using probability distributions
• A 2-3 mm high-resolution molecular line survey towards the centre of the nearby spiral galaxy NGC 6946
• The turbulent gas structure in the centers of NGC253 and the Milky Way
• Understanding if molecular ratios can be used as diagnostics of AGN and starburst activity: The case of NGC 1068
• An ALCHEMI inspection of sulphur-bearing species towards the central molecular zone of NGC 253
• ALMA Sub-arcsec-resolution 183 GHz H2O and Dense Molecular Line Observations of Nearby Ultraluminous Infrared Galaxies
• Complex Organic Molecules towards the central molecular zone of NGC 253
• Surveying the Whirlpool at Arcseconds with NOEMA (SWAN) II: Survey design and observations
• A ring-shaped starburst as a galactic wind-generating mechanism: Morphology, emission, and mass ejection