The radio - far infrared correlation in the faintest star forming dwarf galaxies

Abstract

We study the radio - far-infrared (FIR) correlation in a sample of faint dwarf irregular galaxies using NVSS data for 1.4 GHz radio flux, Spitzer MIPS 70 um data for FIR flux, and GALEX FUV data to estimate the star formation rates (SFR). Since our target galaxies are extremely faint, we stack images of many galaxies together to estimate the average radio and FIR fluxes. We find that for a given SFR both 70 um and 1.4 GHz fluxes are low compared to the calibration for large spirals. Nonetheless, the ratio of 70 um to 1.4 GHz flux agrees within errorbars with that seen for large galaxies. The radio-FIR correlation thus appears to be the result of a 'conspiracy'. We use the SFR to estimate the non-thermal fraction of the 1.4 GHz radio emission and find it to be around 50%, much smaller than the 90% typical for spirals. We also estimate the equipartition magnetic field and find it to be ~ 2 microgauss, about five times smaller than that typical for spirals.

5 pages, 1 figure, 3 tables. Accepted for publication in MNRAS Letters. The definitive version is available at www.blackwell-synergy.com

References in corpus (11)

• Common-Resolution Convolution Kernels for Space- and Ground-Based Telescopes
• Revised equipartition & minimum energy formula for magnetic field strength estimates from radio synchrotron observations
• FIGGS: Faint Irregular Galaxies GMRT Survey - Overview, observations and first results
• Magnetic Fields in Starburst Galaxies and The Origin of the FIR-Radio Correlation
• Magnetic Field Seeding by Galactic Winds
• Magnetic fields in Local Group dwarf irregulars
• A Radio and Optical Polarization Study of the Magnetic Field in the Small Magellanic Cloud
• The MicroJy and NanoJy Radio Sky: Source Population and Multi-wavelength Properties
• GMRT 333 MHz observations of 6 nearby normal galaxies
• Deep Radio Continuum Imaging of the Dwarf Irregular Galaxy IC10: Tracing Star Formation and Magnetic Fields
• Small Bites: Star formation recipes in extreme dwarfs

Cited by in corpus (20)

• A new interpretation of the far-infrared - radio correlation and the expected breakdown at high redshift
• Radio jets from AGN in dwarf galaxies in the COSMOS survey: mechanical feedback out to redshift $\sim$3.4
• A Radio Source Coincident with the Superluminous Supernova PTF10hgi: Evidence for a Central Engine and an Analogue of the Repeating FRB121102?
• The non-linear infrared-radio correlation of low-z galaxies: implications for redshift evolution, a new radio SFR recipe, and how to minimize selection bias
• Radio--Far infrared correlation in "blue cloud" galaxies with 0<z<1.2
• Local Group dSph radio survey with ATCA (II): Non-thermal diffuse emission
• Late-Time Radio and Millimeter Observations of Superluminous Supernovae and Long Gamma Ray Bursts: Implications for Obscured Star Formation, Central Engines, and Fast Radio Bursts
• The far-infrared - radio correlation in dwarf galaxies
• New insights into the interstellar medium of the dwarf galaxy IC 10: connection between magnetic fields, the radio--infrared correlation and star formation
• A Radio Continuum Study of Dwarf Galaxies: 6 cm imaging of Little Things
• Magnetic fields and star formation in low-mass Magellanic-type and peculiar galaxies
• What drives galactic magnetism?
• Global Correlations Between the Radio Continuum, Infrared and CO Emission in Dwarf Galaxies
• Local Volume HI Survey: the far-infrared radio correlation
• Deep uGMRT observations of the ELAIS-North 1 field: statistical properties of radio--infrared relations up to $z\sim$2
• A Spatially Resolved Radio Spectral Index Study of the Dwarf Irregular Galaxy NGC\,1569
• Radio continuum emission from local analogs of high-z faint LAEs: Blueberry galaxies
• Radio properties of Green Pea galaxies
• Far-infrared - radio correlation and magnetic field strength in star-forming early-type galaxies
• Galactic Traversability: A New Concept for Extragalactic SETI