Aims. We present the first public release of high-quality data products (DR1) from Hi-GAL, the Herschel infrared Galactic Plane Survey. Hi-GAL is the keystone of a suite of continuum Galactic plane surveys from the near-IR to the radio and covers five wavebands at 70, 160, 250, 350 and 500 µm, encompassing the peak of the spectral energy distribution of cold dust for 8 < ∼ T < ∼ 50 K. This first Hi-GAL data release covers the inner Milky Way in the longitude range 68 • > ∼ > ∼ −70 • in a |b| ≤ 1 • latitude strip. Methods. Photometric maps have been produced with the ROMAGAL pipeline, which optimally capitalizes on the excellent sensitivity and stability of the bolometer arrays of the Herschel PACS and SPIRE photometric cameras. It delivers images of exquisite quality and dynamical range, absolutely calibrated with Planck and IRAS, and recovers extended emission at all wavelengths and all spatial scales, from the point-spread function to the size of an entire 2 • × 2 • "tile" that is the unit observing block of the survey. The compact source catalogues were generated with the CuTEx algorithm, which was specifically developed to optimise source detection and extraction in the extreme conditions of intense and spatially varying background that are found in the Galactic plane in the thermal infrared. Results. Hi-GAL DR1 images are cirrus noise limited and reach the 1σ-rms predicted by the Herschel Time Estimators for parallel-mode observations at 60 s −1 scanning speed in relatively low cirrus emission regions. Hi-GAL DR1 images will be accessible through a dedicated web-based image cutout service. The DR1 Compact Source Catalogues are delivered as single-band photometric lists containing, in addition to source position, peak, and integrated flux and source sizes, a variety of parameters useful to assess the quality and reliability of the extracted sources. Caveats and hints to help in this assessment are provided. Flux completeness limits in all bands are determined from extensive synthetic source experiments and greatly depend on the specific line of sight along the Galactic plane because the background strongly varies as a function of Galactic longitude. Hi-GAL DR1 catalogues contain 123210, 308509, 280685, 160972, and 85460 compact sources in the five bands.

We present a re-reduction and expansion of the Bolocam Galactic Plane Survey, first presented by Aguirre et al. (2011a) and Rosolowsky et al. (2010a). The BGPS is a 1.1 mm survey of dust emission in the Northern galactic plane, covering longitudes −10 • < < 90 • and latitudes |b| < 0.5 • with a typical 1 − σ RMS sensitivity of 30-100 mJy in a ∼ 33 beam. Version 2 of the survey includes an additional ∼ 20 square degrees of coverage in the 3rd and 4th quadrants and ∼ 2 square degrees in the 1st quadrant. The new data release has improved angular recovery, with complete recovery out to ∼ 80 and partial recovery to ∼ 300 , and reduced negative bowls around bright sources resulting from the atmospheric subtraction process. We resolve the factor of 1.5 flux calibration offset between the v1.0 data release and other data sets and determine that there is no offset between v2.0 and other data sets. The v2.0 pointing accuracy is tested against other surveys and demonstrated to be accurate and an improvement over v1.0. We present simulations and tests of the pipeline and its properties, including measurements of the pipeline's angular transfer function.The Bolocat cataloging tool was used to extract a new catalog, which includes 8594 sources, with 591 in the expanded regions. We have demonstrated that the Bolocat 40 and 80 apertures are accurate even in the presence of strong extended background emission. The number of sources is lower than in v1.0, but the amount of flux and area included in identified sources is larger.

Hi-GAL is a large-scale survey of the Galactic plane, performed with Herschel in five infrared continuum bands between 70 and 500 µm. We present a band-merged catalogue of spatially matched sources and their properties derived from fits to the spectral energy distributions (SEDs) and heliocentric distances, based on the photometric catalogs presented in Molinari et al. (2016a), covering the portion of Galactic plane −71.0 • < < 67.0 • . The band-merged catalogue contains 100922 sources with a regular SED, 24584 of which show a 70 µm counterpart and are thus considered proto-stellar, while the remainder are considered starless. Thanks to this huge number of sources, we are able to carry out a preliminary analysis of early stages of star formation, identifying the conditions that characterise different evolutionary phases on a statistically significant basis. We calculate surface densities to investigate the gravitational stability of clumps and their potential to form massive stars. We also explore evolutionary status metrics such as the dust temperature, luminosity and bolometric temperature, finding that these are higher in proto-stellar sources compared to prestellar ones. The surface density of sources follows an increasing trend as they evolve from pre-stellar to proto-stellar, but then it is found to decrease again in the majority of the most evolved clumps. Finally, we study the physical parameters of sources with respect to Galactic longitude and the association with spiral arms, finding only minor or no differences between the average evolutionary status of sources in the fourth and first Galactic quadrants, or between "on-arm" and "inter-arm" positions.

We tested the validity of the three Larson relations in a sample of 213 massive clumps selected from the Herschel Hi-GAL survey and combined with data from the MALT90 survey of 3mm emission lines. The clumps have been divided in 5 evolutionary stages to discuss the Larson relations also as function of evolution. We show that this ensemble does not follow the three Larson relations, regardless of clump evolutionary phase. A consequence of this breakdown is that the virial parameter α vir dependence with mass (and radius) is only a function of the gravitational energy, independent of the kinetic energy of the system, and α vir is not a good descriptor of clump dynamics. Our results suggest that clumps with clear signatures of infall motions are statistically indistinguishable from clumps with no such signatures. The observed non-thermal motions are not necessarily ascribed to turbulence acting to sustain the gravity, but they may be due to the gravitational collapse at the clump scales. This seems particularly true for the most massive (M 1000 M ⊙ ) clumps in the sample, where also exceptionally high magnetic fields may not be enough to stabilize the collapse.

The Bolocam Galactic Plane Survey (BGPS) data for a six square degree region of the Galactic plane containing the Galactic center is analyzed and compared to infrared and radio continuum data. The BGPS 1.

The evolutionary classification of massive clumps that are candidate progenitors of high-mass young stars and clusters relies on a variety of independent diagnostics based on observables from the nearinfrared to the radio.A promising evolutionary indicator for massive and dense cluster-progenitor clumps is the L/M ratio between the bolometric luminosity and the mass of the clumps. With the aim of providing a quantitative calibration for this indicator we used SEPIA/APEX to obtain CH 3 C 2 H(J=12-11) observations, that is an excellent thermometer molecule probing densities ≥ 10 5 cm −3 , toward 51 dense clumps with M≥1000M , and uniformly spanning -2 < ∼ Log(L/M) [L /M ] < ∼ 2.3. We identify three distinct ranges of L/M that can be associated to three distinct phases of star formation in massive clumps. For L/M ≤1 no clump is detected in CH 3 C 2 H, suggesting an inner envelope temperature below ∼30K. For 1 < ∼ L/M < ∼ 10 we detect 58% of the clumps, with a temperature between ∼30 and ∼35 K independently from the exact value of L/M; such clumps are building up luminosity due to the formation of stars, but no star is yet able to significantly heat the inner clump regions. For L/M > ∼ 10 we detect all the clumps, with a gas temperature rising with Log(L/M), marking the appearance of a qualitatively different heating source within the clumps; such values are found towards clumps with UCHII counterparts, suggesting that the quantitative difference in T vs L/M behaviour above L/M∼10 is due to the first appearance of ZAMS stars in the clumps.

We present the 360○ catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500 μm. This release not only completes the analogous catalogue previously produced by the Hi-GAL collaboration for −71○ ≲ ℓ ≲ 67○, but also meaningfully improves it thanks to a new set of heliocentric distances, 120808 in total. About a third of the 150223 entries are located in the newly added portion of the Galactic plane. A first classification based on detection at 70 μm as a signature of ongoing star-forming activity distinguishes between protostellar sources (23 per cent of the total) and starless sources, with the latter further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including ancillary photometry from λ = 21 to 1100 μm, gives the source luminosity and other bolometric quantities, while a modified blackbody fitted to data for $\lambda \ge 160~\mu$m yields mass and temperature. All tabulated clump properties are then derived using photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidence of correlation with spiral arm positions.

We present the 1.1 millimeter Bolocam Galactic Plane Survey (BGPS) observations of the Gemini OB1 molecular cloud complex, and targeted NH 3 observations of the BGPS sources. When paired with molecular spectroscopy of a dense gas tracer, millimeter observations yield physical properties such as masses, radii, mean densities, kinetic temperatures and line widths. We detect 34 distinct BGPS sources above 5σ = 0.37 Jy beam −1 with corresponding 5σ detections in the NH 3 (1,1) transition. Eight of the objects show water maser emission (20%). We find a mean millimeter source FWHM of 1.12 pc, and a mean gas kinetic temperature of 20 K for the sample of 34 BGPS sources with detections in the NH 3 (1,1) line. The observed NH 3 line widths are dominated by non-thermal motions, typically found to be a few times the thermal sound speed expected for the derived kinetic temperature. We calculate the mass for each source from the millimeter flux assuming the sources are isothermal and find a mean isothermal mass within a 120 ′′ aperture of 230 ± 180 M ⊙ . We find a total mass of 8,400 M ⊙ for all BGPS sources in the Gemini OB1 molecular cloud, representing 6.5% of the cloud mass. By comparing the millimeter isothermal mass to the virial mass within a radius equal to the mm source size calculated from the NH 3 line widths, we find a mean virial parameter (M vir /M iso ) of 1.0±0.9 for the sample. We find mean values for the distributions of column densities of 1.0 × 10 22 cm −2 for H 2 , and 3.0 × 10 14 cm −2 for NH 3 , giving a mean NH 3 abundance of 3.0 × 10 −8 relative to H 2 . We find volume-averaged densities on the order of 10 3 − 10 4 cm −3 . The sizes and densities suggest that in the Gem OB 1 region the BGPS is detecting the clumps from which stellar clusters form, rather than smaller, higher density cores where single stars or small multiple systems form.