GLOSTAR — Radio Source Catalog II: 28◦ < l < 36◦ and |b| < 1◦,VLA B-configuration

As part of the Global View on Star Formation (GLOSTAR) survey we have used the Karl G. Jansky Very Large Array (VLA) in its B-configuration to observe the part of the Galactic plane between longitudes of 28◦ and 36◦ and latitudes from −1◦ to +1◦ at the C-band (4–8 GHz). To reduce the contamination of extended sources that are not well recovered by our coverage of the (u, v)-plane we discarded short baselines that are sensitive to emission on angular scales < 4′′. The resulting radio continuum images have an angular resolution of 1.′′0, and a sensitivity of ∼ 60 μJy beam−1; making it the most sensitive radio survey covering a large area of the Galactic plane with this angular resolution. An automatic source extraction algorithm was used in combination with visual inspection to identify a total of 3325 radio sources. A total of 1457 radio sources are ≥ 7σ and comprise our highly reliable catalog; 72 of these are grouped as 22 fragmented sources, e.g., multiple components of an extended and resolved source. To explore the nature of the catalogued radio sources we searched for counterparts at millimeter and infrared wavelengths. Our classification attempts resulted in 93 H ii region candidates, 104 radio stars, 64 planetary nebulae, while most of the remaining radio sources are suggested to be extragalactic sources. We investigated the spectral indices (α, S ν ∝ να) of radio sources classified as H ii region candidates and found that many have negative values. This may imply that these radio sources represent young stellar objects that are members of the star clusters around the high mass stars that excite the H ii regions, but not these H ii regions themselves. By comparing the peak flux densities from the GLOSTAR and CORNISH surveys we have identified 49 variable radio sources, most of them with an unknown nature. Additionally, we provide the list of 1866 radio sources detected within 5 to 7σ levels

A Global View on Star Formation: The GLOSTAR Galactic PlaneSurvey: V: 6.7 GHz Methanol Maser Catalogue

Class II methanol (CH3OH) masers are amongst the clearest signposts of recent high-mass star formation (HMSF). A complete catalogue outlines the distribution of star formation in the Galaxy, the number of young star-forming cores, and the physical conditions of their environment. The Global View on Star Formation (GLOSTAR) survey, which is a blind survey in the radio regime of 4–8 GHz, maps the Galactic mid-plane in the radio continuum, 6.7 GHz methanol line, the 4.8 GHz formaldehyde line, and several radio recombination lines. We present the analysis of the observations of the 6.7 GHz CH3OH maser transition using data from the D-configuration of the Very Large Array (VLA). We analyse the data covering Galactic longitudes from −2 ◦ < l < 60◦ and Galactic latitudes of |b| < 1 ◦ . We detect a total of 554 methanol masers, out of which 84 are new, and catalogue their positions, velocity components, and integrated fluxes. With a typical noise level of ∼18 mJy beam−1 , this is the most sensitive unbiased methanol survey for methanol masers to date. We search for dust continuum and radio continuum associations, and find that 97% of the sources are associated with dust, and 12% are associated with radio continuum emission

A global view on star formation: The GLOSTAR Galactic plane survey VIII. Formaldehyde absorption in Cygnus X

Context. Cygnus X is one of the closest and most active high-mass star-forming regions in our Galaxy, making it one of the best laboratories for studying massive star formation. Aims. We aim to investigate the properties of molecular gas structures on different linear scales with 4.8 GHz formaldehyde (H2CO) absorption line in Cygnus X. Methods. As part of the GLOSTAR Galactic plane survey, we performed large scale (7◦×3◦) simultaneous H2CO (11,0–11,1) spectral line and radio continuum imaging observations toward Cygnus X at λ ∼6 cm with the Karl G. Jansky Very Large Array and the Effelsberg-100 m radio telescope. We used auxiliary HI, 13CO (1–0), dust continuum, and dust polarization data for our analysis. Results. Our Effelsberg observations reveal widespread H2CO (11,0–11,1) absorption with a spatial extent of ≳50 pc in Cygnus X for the first time. On large scales of 4.4 pc, the relative orientation between local velocity gradient and magnetic field tends to be more parallel at H2 column densities of ≳1.8×1022cm−2. On the smaller scale of 0.17 pc, our VLA+Effelsberg combined data reveal H2CO (11,0–11,1) absorption only toward three bright HII regions. Our observations demonstrate that H2CO (11,0–11,1) is commonly optically thin. Kinematic analysis supports the assertion that molecular clouds generally exhibit supersonic motions on scales of 0.17–4.4 pc. We show a non-negligible contribution of the cosmic microwave background radiation in producing extended absorption features in Cygnus X. Our observations suggest that H2CO (11,0 − 11,1) can trace molecular gas with H2 column densities of ≳ 5 × 1021 cm−2 (i.e., AV ≳ 5). The ortho-H2CO fractional abundance with respect to H2 has a mean value of 7.0×10−10. A comparison of velocity dispersions on different linear scales suggests that the dominant −3 km s−1 velocity component in the prominent DR21 region has nearly identical velocity dispersions on scales of 0.17–4.4 pc, which deviates from the expected behavior of classic turbulence

A global view on star formation: The GLOSTAR Galactic plane survey. IX. Radio Source Catalog III: 2◦ < ℓ < 28◦, 36◦ < ℓ < 40◦, 56◦ < ℓ < 60◦ and |b| < 1◦, VLA B-configuration

As part of the GLOSTAR (GLObal view of STAR formation in the Milky Way) survey, we present the high-resolution continuum source catalog for the regions (ℓ = 2◦ − 28◦, 36◦ − 40◦, 56◦ − 60◦, & |b| < 1.0◦), observed with the Karl G. Jansky Very Large Array(VLA) in its B-configuration. The continuum images are optimized to detect compact sources on angular scales up to 4′′, and have a typical noise level of 1σ ∼ 0.08 mJy beam−1 for an angular resolution of 1′′, which makes GLOSTAR currently the highest resolution as well as the most sensitive radio survey of the northern Galactic plane at 4–8 GHz. We extracted 13354 sources above a threshold of 5σ and 5437 sources above 7σ that represent the high-reliability catalog. We determined the in band spectral index (α) for the sources in the 7σ-threshold catalog. The mean value is α = −0.6, which indicates that the catalog is dominated by sources emitting non-thermal radio emission. We identified the most common source types detected in radio surveys: 251 H ii region candidates (113 new), 282 planetary nebulae (PNe) candidates (127 new), 784 radio star candidates (581 new), and 4080 extragalactic radio source candidates (2175 new). A significant fraction of H ii regions and PNe candidates have α < −0.1 indicating that these candidates could contain radio jets, winds or outflows from high-mass and low-mass stellar objects. We identified 245 variable radio sources by comparing the flux densities of compact sources from the GLOSTAR survey and the Co-Ordinated Radio ‘N’ Infrared Survey for High-mass star formation (CORNISH), and find that most of them are infrared quiet. The catalog is typically 95% complete for point sources at a flux density of 0.6 mJy ( i.e. typical 7σ level) and the systematic positional uncertainty is ≲ 0 ′′ .1. The GLOSTAR data and catalogs are available online at https://glostar.mpifr-bonn.mpg.de

A global view on star formation: The GLOSTAR Galactic plane survey VIII. Formaldehyde absorption in Cygnus X

Context. Cygnus X is one of the closest and most active high-mass star-forming regions in our Galaxy, making it one of the best laboratories for studying massive star formation. Aims. We aim to investigate the properties of molecular gas structures on different linear scales with 4.8 GHz formaldehyde (H2CO) absorption line in Cygnus X. Methods. As part of the GLOSTAR Galactic plane survey, we performed large scale (7◦×3◦) simultaneous H2CO (11,0–11,1) spectral line and radio continuum imaging observations toward Cygnus X at λ ∼6 cm with the Karl G. Jansky Very Large Array and the Effelsberg-100 m radio telescope. We used auxiliary HI, 13CO (1–0), dust continuum, and dust polarization data for our analysis. Results. Our Effelsberg observations reveal widespread H2CO (11,0–11,1) absorption with a spatial extent of ≳50 pc in Cygnus X for the first time. On large scales of 4.4 pc, the relative orientation between local velocity gradient and magnetic field tends to be more parallel at H2 column densities of ≳1.8×1022 cm−2. On the smaller scale of 0.17 pc, our VLA+Effelsberg combined data reveal H2CO (11,0–11,1) absorption only toward three bright HII regions. Our observations demonstrate that H2CO (11,0–11,1) is commonly optically thin. Kinematic analysis supports the assertion that molecular clouds generally exhibit supersonic motions on scales of 0.17–4.4 pc. We show a non-negligible contribution of the cosmic microwave background radiation in producing extended absorption features in Cygnus X. Our observations suggest that H2CO (11,0 − 11,1) can trace molecular gas with H2 column densities of ≳ 5 × 1021 cm−2 (i.e., AV ≳ 5). The ortho-H2CO fractional abundance with respect to H2 has a mean value of 7.0×10−10. A comparison of velocity dispersions on different linear scales suggests that the dominant −3 km s−1 velocity component in the prominent DR21 region has nearly identical velocity dispersions on scales of 0.17–4.4 pc, which deviates from the expected behavior of classic turbulence