Star formation in the centre of NGC 1808 as observed by ALMA

Abstract

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of 85.69 and 99.02 GHz continuum emission and H42$\alpha$ and H40$\alpha$ lines emission from the central 1~kpc of NGC 1808. These forms of emission are tracers of photoionizing stars but unaffected by dust obscuration that we use to test the applicability of other commonly star formation metrics. An analysis of the spectral energy distributions shows that free-free emission contributes about 60 to 90 per cent of the continuum emission in the 85-100 GHz frequency range, dependent on the region. The star formation rate (SFR) derived from the ALMA free-free emission is $3.1\pm 0.3$~M${}_{\odot }$~yr${}^{-1}$. This is comparable to the SFRs measured from the infrared emission, mainly because most of the bolometric energy from the heavily obscured region is emitted as infrared emission. The radio 1.5~GHz emission yields a SFR 25 per cent lower than the ALMA value, probably because of the diffusion of the electrons producing the synchrotron emission beyond the star-forming regions. The SFRs measured from the extinction-corrected H$\alpha$ line emission are about 40 to 65 per cent of the SFR derived from the ALMA data, likely because this metric was not calibrated for high extinction regions. Some SFRs based on extinction-corrected ultraviolet emission are similar to those from ALMA and infrared data, but given that the ultraviolet terms in the extinction correction equations are very small, these metrics seem inappropriate to apply to this dusty starburst.

18 pages, 7 figures, 10 tables, accepted for publication in MNRAS

References in corpus (24)

• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• CASA, the Common Astronomy Software Applications for Radio Astronomy
• The MUSE second-generation VLT instrument
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• The GALEX Ultraviolet Atlas of Nearby Galaxies
• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• The Data Processing Pipeline for the MUSE Instrument
• ALMA Imaging of HCN, CS and dust in Arp 220 and NGC 6240
• The Effect of Active Galactic Nuclei on the Mid-Infrared Aromatic Features
• The Incidence of Highly-Obscured Star-Forming Regions in SINGS Galaxies
• Probing the Physics of Narrow Line Regions in Active Galaxies II: The Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7)
• ALMA observations of 99 GHz free-free and H40$\alpha$ line emission from star formation in the centre of NGC 253
• PHANGS-JWST First Results: Destruction of the PAH molecules in HII regions probed by JWST and MUSE
• PAH Strength and the Interstellar Radiation Field around the Massive Young Cluster NGC3603
• Super Star Clusters in the Central Starburst of NGC 4945
• Free-free and H42alpha emission from the dusty starburst within NGC 4945 as observed by ALMA
• Physics of ULIRGs with MUSE and ALMA: The PUMA project I. Properties of the survey and first MUSE data results
• Star formation and gas flows in the centre of the NUGA galaxy NGC 1808 observed with SINFONI
• ALMA Observations of Atomic Carbon [C I] (${{}^3\mathrm{P}}_1\to {{}^3\mathrm{P}}_0$) and Low-$J$ CO Lines in the Starburst Galaxy NGC 1808
• Tests of star formation metrics in the low metallicity galaxy NGC 5253 using ALMA observations of H30$\alpha$ line emission
• Evolution of Molecular Clouds in the Superwind Galaxy NGC 1808 Probed by ALMA Observations
• Star formation traced by optical and millimeter hydrogen recombination lines and free-free emissions in the dusty merging galaxy NGC 3256 -- MUSE/VLT and ALMA synergy
• The relationship between polycyclic aromatic hydrocarbon emission and far-infrared dust emission from NGC 2403 and M83
• Non-detection of Broad Hydrogen Radio Recombination Lines in Circinus Galaxy

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