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Register a new userMIRIS Pa{alpha} Galactic Plane Survey. I. Comparison with IPHAS H{alpha} in l = 96{deg}-116{deg}
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The Multipurpose InfraRed Imaging System (MIRIS) performed the MIRIS Pa{alpha} Galactic Plane Survey (MIPAPS), which covers the entire Galactic plane within the latitude range of -3{deg} < b < +3{deg} at Pa{alpha} (1.87 um). We present the first result of the MIPAPS data extracted from the longitude range of l = 96.5{deg}-116.3{deg}, and demonstrate the data quality and scientific potential of the data by comparing them with H{alpha} maps obtained from the INT Photometric H{alpha} Survey (IPHAS) data. We newly identify 90 H II region candidates in the WISE H II region catalog as definite H II regions by detecting the Pa{alpha} and/or H{alpha} recombination lines, out of which 53 H II regions are detected at Pa{alpha}. We also report the detection of additional 29 extended and 18 point-like sources at Pa{alpha}. We estimate the E(B-V) color excesses and the total Lyman continuum luminosities for H II regions by combining the MIPAPS Pa{alpha} and IPHAS H{alpha} fluxes. The E(B-V) values are found to be systematically lower than those estimated from point stars associated with H II regions. Utilizing the MIPAPS Pa{alpha} and IPHAS H{alpha} images, we obtain an E(B-V) map for the entire region of the H II region Sh2-131 with an angular size of ~2.5{deg}. The E(B-V) map shows not only numerous high-extinction filamentary features but also negative E(B-V) regions, indicating H{alpha} excess. The H{alpha} excess and the systematic underestimation of E(B-V) are attributed to light scattered by dust.
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We present the Forgotten Quadrant Survey (FQS), an ESO large project that used the 12m antenna of the Arizona Radio Observatory to map the Galactic Plane in the range 220deg$<l<$240deg and -2.5deg$<b<$0deg, both in $^{12}$CO(1-0) and $^{13}$CO(1-0), at a spectral resolution of 0.65 km s$^{-1}$ and 0.26 km s$^{-1}$. Our dataset allows us to easily identify how the molecular dense gas is organised at different spatial scales: from the giant clouds with their denser filamentary networks, down to the clumps and cores that host the newborn stars and to obtain reliable estimates of their key physical parameters. We present the first release of the FQS data and discuss their quality. Spectra with 0.65 km s$^{-1}$ velocity channels have a noise ranging from 0.8 K to 1.3 K for $^{12}$CO(1-0) and from 0.3 K to 0.6 K for $^{13}$CO(1-0). In this paper, we used the $^{12}$CO(1-0) spectral cubes to produce a catalogue of 263 molecular clouds. This is the first selfconsistent, statistical catalogue of molecular clouds of the outer Galaxy, obtained with a subarcminute spatial resolution and therefore able to detect not only the classical giant molecular clouds, but also the small clouds and to resolve the cloud structure at the subparsec scale up to a distance of a few kpc. We found two classes of objects: structures with size above a few parsecs that are typical molecular clouds and may be self-gravitating, and subparsec structures that cannot be in gravitational equilibrium and are likely transient or confined by external pressure. We used the ratio between the Herschel H$_2$ column density and the integrated intensity of the CO lines to calculate the CO conversion factor and we found mean values of (3.3$pm$1.4)$times 10^{20}$ cm$^{-2}$(K km s$^{-1})^{-1}$ and (1.2$pm$0.4)$times 10^{21}$ cm$^{-2}$(K km s$^{-1})^{-1}$, for $^{12}$CO(1-0) and $^{13}$CO(1-0), respectively.
Surveys of the Milky Way at various wavelengths have changed our view of star formation in our Galaxy considerably in recent years. In this paper we give an overview of the GLOSTAR survey, a new survey covering large parts (145 square degrees) of the northern Galactic plane using the Karl G. Jansky Very Large Array (JVLA) in the frequency range 4-8 GHz and the Effelsberg 100-m telescope. This provides for the first time a radio survey covering all angular scales down to 1.5 arcsecond, similar to complementary near-IR and mid-IR galactic plane surveys. We outline the main goals of the survey and give a detailed description of the observations and the data reduction strategy. In our observations we covered the radio continuum in full polarization, as well as the 6.7 GHz methanol maser line, the 4.8~GHz formaldehyde line, and seven radio recombination lines. The observations were conducted in the most compact D configuration of the VLA and in the more extended B configuration. This yielded spatial resolutions of 18 and 1.5 for the two configurations, respectively. We also combined the D configuration images with the Effelsberg 100-m data to provide zero spacing information, and we jointly imaged the D- and B-configuration data for optimal sensitivity of the intermediate spatial ranges. Here we show selected results for the first part of the survey, covering the range of 28 deg <l<36 deg and |b|< 1 deg, including the full low-resolution continuum image, examples of high-resolution images of selected sources, and the first results from the spectral line data.
Synchrotron emission pervades the Galactic plane at low radio frequencies, originating from cosmic ray electrons interacting with the Galactic magnetic field. Using a low-frequency radio telescope, the Murchison Widefield Array (MWA), we measure the free-free absorption of this Galactic synchrotron emission by intervening HII regions along the line of sight. These absorption measurements allow us to calculate the Galactic cosmic-ray electron emissivity behind and in front of 47 detected HII regions in the region $250^circ < l < 355^circ$, $|b| < 2^circ$. We find that all average emissivities between the HII regions and the Galactic edge along the line of sight ($epsilon_b$) are in the range of 0.24$,,sim,,$0.70$,,$K$,,$pc$^{-1}$ with a mean of 0.40$,,$K$,,$pc$^{-1}$ and a variance of 0.10$,,$K$,,$pc$^{-1}$ at 88$,,$MHz. Our best model, the Two-circle model, divides the Galactic disk into three regions using two circles centring on the Galactic centre. It shows a high emissivity region near the Galactic centre, a low emissivity region near the Galactic edge, and a medium emissivity region between these two regions, contrary to the trend found by previous studies.
The INT Photometric Halpha Survey of the Northern Galactic Plane (IPHAS) is a 1800 square degrees CCD survey of the northern Milky Way spanning the latitude range -5 < b < +5 (degrees) and reaching down to r ~ 20 (10-sigma). It may increase the number of known northern emission line sources by an order of magnitude. Representative observations and an assessment of point-source data from IPHAS, now underway, are presented. The data obtained are Wide Field Camera images in Halpha narrow-band, and Sloan r and i broad-band, filters. We simulate IPHAS (r - Halpha, r - i) point-source colours using a spectrophotometric library of stellar spectra and available filter transmission profiles: this gives expected colours for (i) solar-metallicity stars, without Halpha emission, and (ii) emission line stars. Comparisons with Aquila field observations show that simulated normal star colours reproduce the data well for spectral types earlier than M. Spectroscopic follow-up of a Cepheus field confirms that sources lying above the main stellar locus in the (r - Halpha, r - i) plane are emission line objects, with very few failures. Examples of Halpha deficit objects -- a white dwarf and a carbon star -- are shown to be readily distinguished by their IPHAS colours. The role IPHAS can play in studies of nebulae is discussed briefly, and illustrated by a continuum-subtracted mosaic image of the SNR, Shajn 147. The final catalogue of IPHAS point sources will contain photometry on ~80 million objects. (abridged)
We report H$alpha$ filter photometry for 197 northern hemisphere planetary nebulae (PNe) obtained using imaging data from the IPHAS survey. H$alpha$+[N II] fluxes were measured for 46 confirmed or possible PNe discovered by the IPHAS survey and for 151 previously catalogued PNe that fell within the area of the northern Galactic Plane surveyed by IPHAS. After correcting for [N II] emission admitted by the IPHAS H$alpha$ filter, the resulting H$alpha$ fluxes were combined with published radio free-free fluxes and H$beta$ fluxes, in order to estimate mean optical extinctions to 143 PNe using ratios involving their integrated Balmer line fluxes and their extinction-free radio fluxes. Distances to the PNe were then estimated using three different 3D interstellar dust extinction mapping methods, including the IPHAS-based H-MEAD algorithm of Sale (2014). These methods were used to plot dust extinction versus distance relationships for the lines of sight to the PNe; the intercepts with the derived dust optical extinctions allowed distances to the PNe to be inferred. For 17 of the PNe in our sample reliable Gaia DR2 distances were available and these have been compared with the distances derived using three different extinction mapping algorithms as well as with distances from the nebular radius vs. H$alpha$ surface brightness relation of Frew et al. (2016). That relation and the H-MEAD extinction mapping algorithm yielded the closest agreement with the Gaia DR2 distances.
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