An official website of the United States government
Abstract We present early results from the CO Mapping Array Project (COMAP) Galactic Plane Survey conducted between 2019 June and 2021 April, spanning 20° <ℓ< 40° in Galactic longitude and ∣b∣ < 1.°5 in Galactic latitude with an angular resolution of 4.′5. We present initial results from the first part of the survey, including the diffuse emission and spectral energy distributions of Hiiregions and supernova remnants (SNRs). Using low- and high-frequency surveys to constrain free–free and thermal dust emission contributions, we find evidence of excess flux density at 30 GHz in six regions, which we interpret as anomalous microwave emission. Furthermore we model ultracompact Hiicontributions using data from the 5 GHz CORNISH catalog and reject these as the cause of the 30 GHz excess. Six known SNRs are detected at 30 GHz, and we measure spectral indices consistent with the literature or show evidence of steepening. The flux density of the SNR W44 at 30 GHz is consistent with a power-law extrapolation from lower frequencies with no indication of spectral steepening in contrast with recent results from the Sardinia Radio Telescope. We also extract five hydrogen radio recombination lines (RRLs) to map the warm ionized gas, which can be used to estimate electron temperatures or to constrain continuum free–free emission. The full COMAP Galactic Plane Survey, to be released in 2023/2024, will spanℓ∼ 20°–220° and will be the first large-scale radio continuum and RRL survey at 30 GHz with 4.′5 resolution.
more »
« less
COMAP Galactic science I: observations of spinning dust emission at 30 GHz in dark clouds surrounding the λ-Orionis H ii region
ABSTRACT Anomalous microwave emission (AME) is a major component of Galactic emission in the frequency band 10–60 GHz and is commonly modelled as rapidly rotating spinning dust grains. The photodissociation region (PDR) at the boundary of the $$\lambda$$-Orionis H ii region has been identified by several recent analyses as one of the brightest spinning dust-emitting sources in the sky. We investigate the Barnard 30 dark cloud, a dark cloud embedded within the $$\lambda$$-Orionis PDR. We use total-power observations of Barnard 30 from the CO Mapping Array Project (COMAP) pathfinder instrument at 26–34GHz with a resolution of 4.5 arcmin alongside existing data from Planck, WISE, IRAS, ACT, and the 1.447 GHz GALFACTS survey. We use aperture photometry and template fitting to measure the spectral energy distribution of Barnard 30. We find that the spinning dust is the dominant emission component in the 26–34GHz range at the $$6\, \sigma$$ level ($$S_{30\, \mathrm{GHz}} = 3.35\pm 0.56$$ Jy). From correlating COMAP data with dust templates we find no evidence that polycyclic aromatic hydrocarbons are the preferred carrier for the spinning dust emission, suggesting that the spinning dust carriers are due to a mixed population of very small grains. Finally, we find evidence for variations in spinning dust emissivity and peak frequency within Barnard 30, and that these variations are possibly driven by changes in dust grain population and the total radiation field. Confirming the origin of the variations in the spinning dust spectrum will require both future COMAP observations at 15 GHz combined with spectroscopic mid-infrared data of Barnard 30.
more »
« less
- Award ID(s):
- 2206834
- PAR ID:
- 10563465
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 536
- Issue:
- 3
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 2914-2935
- Size(s):
- p. 2914-2935
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The CO Mapping Array Project (COMAP) is a carbon monoxide (CO) line intensity mapping experiment using a 19-feed 26–34 GHz focal plane spectrometer array on a 10.4 m dish at the Owens Valley Radio Observatory. We are developing a water vapor radiometer (WVR) that continuously measures the temporal variability of the atmosphere’s water vapor content along the telescope’s line of sight to better calibrate the COMAP science data. The WVR is designed to monitor the rotational transition line of water vapor around 22.2 GHz, with a spectral measurement between 18 and 26 GHz and a measurement of continuum at 28–30 GHz. Here we describe the COMAP WVR instrument system.more » « less
-
Abstract We introduce COMAP-EoR, the next generation of the Carbon Monoxide Mapping Array Project aimed at extending CO intensity mapping to the Epoch of Reionization. COMAP-EoRsupplements the existing 30 GHz COMAP Pathfinder with two additional 30 GHz instruments and a new 16 GHz receiver. This combination of frequencies will be able to simultaneously map CO(1–0) and CO(2–1) at reionization redshifts (z∼ 5–8) in addition to providing a significant boost to thez∼ 3 sensitivity of the Pathfinder. We examine a set of existing models of the EoR CO signal, and find power spectra spanning several orders of magnitude, highlighting our extreme ignorance about this period of cosmic history and the value of the COMAP-EoRmeasurement. We carry out the most detailed forecast to date of an intensity mapping cross correlation, and find that five out of the six models we consider yield signal to noise ratios (S/Ns) ≳ 20 for COMAP-EoR, with the brightest reaching a S/N above 400. We show that, for these models, COMAP-EoRcan make a detailed measurement of the cosmic molecular gas history fromz∼ 2–8, as well as probe the population of faint, star-forming galaxies predicted by these models to be undetectable by traditional surveys. We show that, for the single model that does not predict numerous faint emitters, a COMAP-EoR-type measurement is required to rule out their existence. We briefly explore prospects for a third-generation Expanded Reionization Array (COMAP-ERA) capable of detecting the faintest models and characterizing the brightest signals in extreme detail.more » « less
-
ABSTRACT We characterize the kinematic and magnetic properties of H i filaments located in a high Galactic latitude region (165° < α < 195° and 12° < δ < 24°). We extract three-dimensional filamentary structures using fil3d from the Galactic Arecibo L-Band Feed Array H i (GALFA-H i) survey 21-cm emission data. Our algorithm identifies coherent emission structures in neighbouring velocity channels. Based on the mean velocity, we identify a population of local and intermediate velocity cloud (IVC) filaments. We find the orientations of the local (but not the IVC) H i filaments are aligned with the magnetic field orientations inferred from Planck 353 GHz polarized dust emission. We analyse position–velocity diagrams of the velocity-coherent filaments, and find that only 15 per cent of filaments demonstrate significant major-axis velocity gradients with a median magnitude of 0.5 km s−1 pc−1, assuming a fiducial filament distance of 100 pc. We conclude that the typical diffuse H i filament does not exhibit a simple velocity gradient. The reported filament properties constrain future theoretical models of filament formation.more » « less
-
Context. The Milky Way’s central molecular zone (CMZ) has been measured to form stars ten times less efficiently than in the Galactic disk, based on emission from high-mass stars. However, the CMZ’s low-mass (⩽2M⊙) protostellar population, which accounts for most of the initial stellar mass budget and star formation rate (SFR), is poorly constrained observationally due to limited sensitivity and resolution. Aims. We aim to perform a cloud-wide census of the protostellar population in three massive CMZ clouds. Methods. We present the Dual-band Unified Exploration of three CMZ Clouds (DUET) survey, targeting the 20 km s−1cloud, Sgr C, and the dust ridge cloud “e” using the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 and 3 mm. The mosaicked observations achieve a comparable resolution of 0.′′2–0.′′3 (∼2000 au) and a sky coverage of 8.3–10.4 arcmin2, respectively. Results. We report 563 continuum sources at 1.3 mm and 330 at 3 mm, respectively, and a dual-band catalog with 450 continuum sources. These sources are marginally resolved at a resolution of 2000 au. We find a universal deviation (>70% of the source sample) from commonly used dust modified blackbody (MBB) models, characterized by either low spectral indices or low brightness temperatures. Conclusions. Three possible explanations are discussed for the deviation. (1) Optically thick class 0/I young stellar objects (YSOs) with a very small beam filling factor can lead to lower brightness temperatures than what MBB models predict. (2) Large dust grains with millimeter or centimeter in size have more significant self-scattering, and frequency-dependent albedo could therefore cause lower spectral indices. (3) Free-free emission over 30 μJy can severely contaminate dust emission and cause low spectral indices for milliJansky sources, although the number of massive protostars (embedded UCHIIregions) needed is infeasibly high for the normal stellar initial mass function. A reliable measurement of the SFR at low protostellar masses will require future work to distinguish between these possible explanations.more » « less
