Where's the Dust?: The Deepening Anomaly of Microwave Emission in NGC 4725 B

Abstract

We present new Atacama Large Millimeter Array (ALMA) observations towards NGC 4725 B, a discrete, compact, optically-faint region within the star-forming disk of the nearby galaxy NGC 4725 that exhibits strong anomalous microwave emission (AME). These new ALMA data include continuum observations centered at 92, 133, 203, and 221 GHz accompanied by spectral observations of the ${}^{12}$CO ($J=2\to 1$) line. NGC 4725 B is detected in the continuum at all frequencies, although the detection at 203 GHz is marginal. While molecular gas is not detected at the exact location of NGC 4725 B, there is molecular gas in the immediate vicinity (i.e., $\lesssim 100$ pc) along with associated diffuse 8 $\mu$m emission. When combined with existing Very Large Array continuum data at 1.5, 3, 5.5, 9, 14, 22, 33, and 44 GHz, the spectrum is best fit by a combination of AME, synchrotron, and free-free emission that is free-free absorbed below $\sim 6$ GHz. Given the strength of the AME, there is surprisingly no indication of millimeter dust emission associated with NGC 4725 B on $\lesssim$6\arcsec~spatial scales at the sensitivity of the ALMA interferometric data. Based on the properties of the nearest molecular gas complex and the inferred star formation rate, NGC 4725 B is consistent with being an extremely young ($\sim 3-5$ Myr) massive ($\lesssim 10^5{M}_{\odot }$) cluster that is undergoing active cluster feedback. However, the lack of millimeter thermal dust emission is difficult to reconcile with a spinning dust origin of the 30 GHz emission. On the other hand, modeling NGC 4725 B as a new class of background radio galaxy is also unsatisfactory.

arXiv comment15 pages, 4 figures, accepted for publication in ApJ Letters

References in corpus (61)

• emcee: The MCMC Hammer
• The NumPy array: a structure for efficient numerical computation
• On the variation of the Initial Mass Function
• Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant
• Embedded Clusters in Molecular Clouds
• The CO-to-H2 Conversion Factor
• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• SINGS: The SIRTF Nearby Galaxies Survey
• Young massive star clusters
• Molecular Gas at High Redshift
• Calibrating Extinction-Free Star Formation Rate Diagnostics with 33GHz Free-Free Emission in NGC6946
• HERACLES: The HERA CO-Line Extragalactic Survey
• A multi-scale multi-frequency deconvolution algorithm for synthesis imaging in radio interferometry
• Optical Spectroscopy and Nebular Oxygen Abundances of the Spitzer/SINGS Galaxies
• Multi-Scale CLEAN deconvolution of radio synthesis images
• Electric Dipole Radiation from Spinning Dust Grains
• KINGFISH -- Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel: Survey Description and Image Atlas
• GOALS: The Great Observatories All-Sky LIRG Survey
• An Anomalous Component of Galactic Emission
• Detection and Characterization of Cold Interstellar Dust and PAH Emission from COBE Observations
• Microwave Emission at High Galactic Latitudes
• Legacy ExtraGalactic UV Survey (LEGUS) with The Hubble Space Telescope. I. Survey Description
• Magnetic Dipole Microwave Emission from Dust Grains
• Ionizing Photon Emission Rates from O- and Early B-type Stars and Clusters
• Planck 2018 results. XI. Polarized dust foregrounds
• Planck early results. XX. New light on anomalous microwave emission from spinning dust grains
• Planck intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization
• Planck intermediate results. XVII. Emission of dust in the diffuse interstellar medium from the far-infrared to microwave frequencies
• A refined model for spinning dust radiation
• Legacy ExtraGalactic UV Survey with The Hubble Space Telescope. Stellar cluster catalogues and first insights into cluster formation and evolution in NGC 628
• Magnetic Nanoparticles in the Interstellar Medium: Emission Spectrum and Polarization
• The Star Formation Efficiency per Free Fall Time in Nearby Galaxies
• ALMA Observations of the Antennae Galaxies: I. A New Window on a Prototypical Merger
• Spinning dust emission: the effect of rotation around a non-principal axis
• The State-of-Play of Anomalous Microwave Emission (AME) Research
• The Detection of Anomalous Dust Emission in the Nearby Galaxy NGC 6946
• The Australia Telescope 20GHz (AT20G) Survey: analysis of the extragalactic source sample
• Effective Radii of Young, Massive Star Clusters in Two LEGUS Galaxies
• GMC Evolutions in the Nearby Spiral Galaxy M33
• Modeling the Anomalous Microwave Emission with Spinning Nanoparticles: No PAHs Required
• Physical properties in young radio sources. VLBA observations of high frequency peaking radio sources
• The young star cluster population of M51 with LEGUS - II. Testing environmental dependencies
• Spinning Dust Emission: Effects of irregular grain shape, transient heating and comparison with WMAP results
• A Case Against Spinning PAHs as the Source of the Anomalous Microwave Emission
• Anomalous Microwave Emission from the HII region RCW175
• Molecular gas and dust properties of galaxies from the Great Observatories All-sky LIRG Survey
• Spinning dust emission from ultrasmall silicates: emissivity and polarization spectrum
• Spitzer characterisation of dust in an anomalous emission region: the Perseus cloud
• Microwave observations of spinning dust emission in NGC6946
• Spatially Resoved 12CO(2-1)/12CO(1-0) in the Starburst Galaxy NGC 253: Assessing Optical Depth to Constrain the Molecular Mass Outflow Rate
• The Star Formation in Radio Survey: 3 - 33 GHz Imaging of Nearby Galaxy Nuclei and Extranuclear Star-forming Regions
• Anomalous microwave emission from spinning nanodiamonds around stars
• Characterizing Extragalactic Anomalous Microwave Emission in NGC 6946 with CARMA
• The Star Formation in Radio Survey: Jansky Very Large Array 33 GHz Observations of Nearby Galaxy Nuclei and Extranuclear Star-Forming Regions
• Strong evidence of Anomalous Microwave Emission from the flux density spectrum of M31
• A New Detection of Extragalactic Anomalous Microwave Emission in a Compact, Optically-Faint Region of NGC\,4725
• Microwave Continuum Emission and Dense Gas Tracers in NGC 3627: Combining Jansky VLA and ALMA Observations
• Derivation of an Analytical Approximation of the Spectrum of Spinning Dust Emission
• Asymmetric Drift in the Andromeda Galaxy (M31) as a Function of Stellar Age
• Determining Star Formation Thresholds from Observations
• Excess in the High Frequency Radio Background: Insights from Planck

Cited by in corpus (6)

• Characterizing Compact 15-33 GHz Radio Continuum Sources in Local U/LIRGs
• COLDz: Probing Cosmic Star Formation With Radio Free-free Emission
• QUIJOTE Scientific Results -- VII. Galactic AME sources in the QUIJOTE-MFI Northern Hemisphere Wide-Survey
• Millimeter emission from supermassive black hole coronae
• Far-infrared to centimeter emission of very nearby galaxies with archival data
• The mm-to-cm SED of spiral galaxies. Synergies between NIKA2 and SRT instruments