Search

Aims. To constrain models of high-mass star formation it is important to identify the massive dense cores (MDCs) that are able to form high-mass star(s). This is one of the purposes of the Herschel/HOBYS key programme. Here, we carry out the census and characterise of the properties of the MDCs population of the NGC 6357 H II region. Methods. Our study is based on the Herschel/PACS and SPIRE 70−500 μm images of NGC 6357 complemented with (sub-)millimetre and mid-infrared data. We followed the procedure established by the Herschel/HOBYS consortium to extract ~0.1 pc massive dense cores using the getsources software. We estimated their physical parameters (temperatures, masses, luminosities) from spectral energy distribution (SED) fitting. Results. We obtain a complete census of 23 massive dense cores, amongst which one is found to be IR-quiet and twelve are starless, representing very early stages of the star-formation process. Focussing on the starless MDCs, we have considered their evolutionary status, and suggest that only five of them are likely to form a high-mass star. Conclusions. We find that, contrarily to the case in NGC 6334, the NGC 6357 region does not exhibit any ridge or hub features that are believed to be crucial to the massive star formation process. This study adds support for an empirical model in which massive dense cores and protostars simultaneously accrete mass from the surrounding filaments. In addition, the massive star formation in NGC 6357 seems to have stopped and the hottest stars in Pismis 24 have disrupted the filaments. [ABSTRACT FROM AUTHOR]

G351.776-0.527 is among the most massive, closest, and youngest filaments in the inner Galactic plane and therefore it is an ideal laboratory to study the kinematics of dense gas and mass replenishment on a large scale. In this paper, we present far-infrared and submillimetre wavelength continuum observations combined with spectroscopic C18O (2–1) data of the entire region to study its temperature, mass distribution, and kinematics. The structure is composed of a main elongated region with an aspect ratio of ~23, which is associated with a network of filamentary structures. The main filament has a remarkably constant width of 0.2 pc. The total mass of the network (including the main filament) is ≥2600M⊙, while we estimate a mass of ~2000M⊙ for the main structure. Therefore, the network harbours a large reservoir of gas and dust that could still be accreted onto the main structure. From the analysis of the gas kinematics, we detect two velocity components in the northern part of the main filament. The data also reveal velocity oscillations in C18O along the spine in the main filament and in at least one of the branches. Considering the region as a single structure, we find that it is globally close to virial equilibrium indicating that the entire structure is approximately in a stable state. [ABSTRACT FROM AUTHOR]

Context. How the diffuse medium of molecular clouds condenses in dense cores and how many of these cores will evolve in protostars is still a poorly understood step of the star formation process. Much progress is being made in this field, thanks to the extensive imaging of star-forming regions carried out with the Herschel Space Observatory. Aims. The Herschel Gould Belt Survey key project mapped the bulk of nearby star-forming molecular clouds in five far-infrared bands with the aim of compiling complete census of prestellar cores and young, embedded protostars. From the complete sample of prestellar cores, we aim at defining the core mass function and studying its relationship with the stellar initial mass function. Young stellar objects (YSOs) with a residual circumstellar envelope are also detected. Methods. In this paper, we present the catalogue of the dense cores and YSOs/protostars extracted from the Herschel maps of the Lupus I, III, and IV molecular clouds. The physical properties of the detected objects were derived by fitting their spectral energy distributions. Results. A total of 532 dense cores, out of which 103 are presumably prestellar in nature, and 38 YSOs/protostars have been detected in the three clouds. Almost all the prestellar cores are associated with filaments against only about one third of the unbound cores and YSOs/protostars. Prestellar core candidates are found even in filaments that are on average thermally subcritical and over a background column density lower than that measured in other star-forming regions so far. The core mass function of the prestellar cores peaks between 0.2 and 0.3 M⊙, and it is compatible with the log-normal shape found in other regions. Herschel data reveal several, previously undetected, protostars and new candidates of Class 0 and Class II with transitional disks. We estimate the evolutionary status of the YSOs/protostars using two independent indicators: the α index and the fitting of the spectral energy distribution from near- to far-infrared wavelengths. For 70% of the objects, the evolutionary stages derived with the two methods are in agreement. Conclusions. Lupus is confirmed to be a very low-mass star-forming region, in terms of both the prestellar condensations and the diffuse medium. Noticeably, in the Lupus clouds we have found star formation activity associated with interstellar medium at low column density, usually quiescent in other (more massive) star-forming regions. [ABSTRACT FROM AUTHOR]

Context. We present the physical and evolutionary properties of prestellar and protostellar clumps in the Herschel Infrared GALactic plane survey (Hi-GAL) in two large areas centered in the Galactic plane and covering the tips of the long Galactic bar at the intersection with the spiral arms. The areas fall in the longitude ranges 19° < ɭ < 33° and 340° < ɭ < 350°, while latitude is-1° < b < 1°. Newly formed high mass stars and prestellar objects are identified and their properties derived and compared. A study is also presented on five giant molecular complexes at the further edge of the bar, identified through ancillary 12CO(1-0) data from the NANTEN observatory. Aims. One of the goals of this analysis is assessing the role of spiral arms in the star-formation processes in the Milky Way. It is, in fact, still a matter of debate if the particular configuration of the Galactic rotation and potential at the tips of the bar can trigger star formation. Methods. The star-formation rate was estimated from the quantity of proto-stars expected to form during the collapse of massive turbulent clumps into star clusters. The expected quantity of proto-stars was estimated by the possible final cluster configurations of a given initial turbulent clump. This new method was developed by applying a Monte Carlo procedure to an evolutionary model of turbulent cores and takes into account the wide multiplicity of sources produced during the collapse. Results. The star-formation rate density values at the tips are 1:2 ± 0:3 × 10-3M/yr kpc2 and 1:5 ± 0:3 × 10-3M/yr kpc2 in the first and fourth quadrant, respectively. The same values estimated on the entire field of view, that is including the tips of the bar and background and foreground regions, are 0:9 ± 0:2 × 10-3M/yr kpc2 and 0:8 ± 0:2 × 10-3M yr kpc2. The conversion e°ciency indicates the percentage amount of material converted into stars and is approximately 0.8% in the first quadrant and 0.5% in the fourth quadrant, and does not show a significant di erence in proximity of the bar. The star forming regions identified through CO contours at the further edge of the bar show star-formation rate and star-formation rate densities larger than the surrounding regions but their conversion e°ciencies are comparable. Conclusions. The tips of the bar show an enhanced star-formation rate with respect to background and foreground regions. However, the conversion e°ciency shows little change across the observed fields suggesting that the star-formation activity at the bar is due to a large amount of dust and molecular material rather than being due to a triggering process. [ABSTRACT FROM AUTHOR]

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° ≳ ℓ ≳ −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. [ABSTRACT FROM AUTHOR]

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° ≳ ℓ ≳ −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. [ABSTRACT FROM AUTHOR]

Context. Theoretical scenarios propose that high-mass stars are formed by disk-mediated accretion. Aims. To test the theoretical predictions on the formation of massive stars, we wish to make a thorough study at high-angular resolution of the structure and kinematics of the dust and gas emission toward the high-mass star-forming region G35.03+0.35, which harbors a disk candidate around a B-type (proto)star. Methods. We carried out ALMA Cycle 0 observations at 870 μm of dust of typical high-density, molecular outflow, and cloud tracers with resolutions of <0.''5. Complementary Subaru COMICS 25 μm observations were carried out to trace the mid-infrared emission toward this star-forming region. Results. The submillimeter continuum emission has revealed a filamentary structure fragmented into six cores, called A-F. The filament could be in quasi-equilibrium taking into account that the mass per unit length of the filament, 200-375 M☉/pc, is similar to the critical mass of a thermally and turbulently supported infinite cylinder, ∼335 M☉/pc. The cores, which are on average separated by ∼0.02 pc, have deconvolved sizes of 1300-3400 AU, temperatures of 35-240 K, H2 densities >107 cm -3, and masses in the range 1-5 M☉, and they are subcritical. Core A, which is associated with a hypercompact Hii region and could be the driving source of the molecular outflow observed in the region, is the most chemically rich source in G35.03+0.35 with strong emission of typical hot core tracers such as CH3CN. Tracers of high density and excitation show a clear velocity gradient along the major axis of the core, which is consistent with a disk rotating about the axis of the associated outflow. The PV plots along the SE-NW direction of the velocity gradient show clear signatures of Keplerian rotation, although infall could also be present, and they are consistent with the pattern of an edge-on Keplerian disk rotating about a star with a mass in the range 5-13 M☉. The high tff/trot ratio for core A suggests that the structure rotates fast and that the accreting material has time to settle into a centrifugally supported disk. Conclusions. G35.03+0.35 is one of the most convincing examples of Keplerian disks rotating about high-mass (proto)stars. This supports theoretical scenarios according to which high-mass stars, at least B-type stars, would form through disk-mediated accretion. [ABSTRACT FROM AUTHOR]

Context. The formation process of high-mass stars (with masses >8 M☉) is still poorly understood, and represents a challenge from both the theoretical and observational points of view. The advent of the Atacama Large Millimeter Array (ALMA) is expected to provide observational evidence to better constrain the theoretical scenarios. Aims. The present study aims at characterizing the high-mass star forming region G35.20-0.74 N, which is found associated with at least one massive outflow and contains multiple dense cores, one of them recently found associated with a Keplerian rotating disk. Methods. We used the radio-interferometer ALMA to observe the G35.20-0.74 N region in the submillimeter continuum and line emission at 350 GHz. The observed frequency range covers tracers of dense gas (e.g., H13CO+, C17O), molecular outflows (e.g., SiO), and hot cores (e.g., CH3CN, CH3OH). These observations were complemented with infrared and centimeter data. Results. The ALMA 870 μm continuum emission map reveals an elongated dust structure (∼0.15 pc long and ∼0.013 pc wide; full width at half maximum) perpendicular to the large-scale molecular outflow detected in the region, and fragmented into a number of cores with masses ∼1-10 M☉ and sizes ∼1600 AU (spatial resolution ∼960 AU). The cores appear regularly spaced with a separation of ∼0.023 pc. The emission of dense gas tracers such as H13CO+, C17O is extended and coincident with the dust elongated structure. The three strongest dust cores show emission of complex organic molecules characteristic of hot cores, with temperatures around 200 K, and relative abundances 0.2-2 × 10-8 for CH3CN and 0.6-5 × 10-6 for CH3OH. The two cores with highest mass (cores A and B) show coherent velocity fields, with gradients almost aligned with the dust elongated structure. Those velocity gradients are consistent with Keplerian disks rotating about central masses of 4-18 M☉. Perpendicular to the velocity gradients we have identified a large-scale precessing jet/outflow associated with core B, and hints of an east-west jet/outflow associated with core A. Conclusions. The elongated dust structure in G35.20-0.74 N is fragmented into a number of dense cores that may form high-mass stars. Based on the velocity field of the dense gas, the orientation of the magnetic field, and the regularly spaced fragmentation, we interpret this elongated structure as the densest part of a 1D filament fragmenting and forming high-mass stars. [ABSTRACT FROM AUTHOR]

Context. Stars form in dense, dusty clumps of molecular clouds, but little is known about their origin, their evolution, and their detailed physical properties. In particular, the relationship between the mass distribution of these clumps (also known as the "clump mass function", or CMF) and the stellar initial mass function (IMF) is still poorly understood. Aims. To better understand how the CMF evolve toward the IMF and to discern the "true" shape of the CMF, large samples of bona-fide pre- and proto-stellar clumps are required. Two such datasets obtained from the Herschel infrared GALactic Plane Survey (Hi-GAL) have been described in Paper I. Robust statistical methods are needed to infer the parameters describing the models used to fit the CMF and to compare the competing models themselves. Methods. In this paper, we apply Bayesian inference to the analysis of the CMF of the two regions discussed in Paper I. First, we determine the posterior probability distribution for each of the fitted parameters. Then, we carry out a quantitative comparison of the models used to fit the CMF. Results. We have compared several methods of sampling posterior distributions and calculating global likelihoods, and we have also analyzed the impact of the choice of priors and the influence of various constraints on the statistical conclusions for the values of model parameters. We find that both parameter estimation and model comparison depend on the choice of parameter priors. Conclusions. Our results confirm our earlier conclusion that the CMFs of the two Hi-GAL regions studied here have very similar shapes but different mass scales. Furthermore, the lognormal model appears to better describe the CMF measured in the two Hi-GAL regions studied here. However, this preliminary conclusion is dependent on the choice of parameter priors. [ABSTRACT FROM AUTHOR]

Context. G29.9-60.02 is a high-mass star-forming cloud observed at 70, 160, 250, 350, and 500 μm as part of the Herschel survey of the Galactic plane (Hi-GAL) during the science demonstration phase. Aims. We wish to conduct a far-infrared study of the sources associated with this star-forming region by estimating their physical properties and evolutionary stage, and investigating the clump mass function, the star formation efficiency and rate in the cloud. Methods. We have identified the Hi-GAL sources associated with the cloud, searched for possible counterparts at centimeter and infrared wavelengths, fitted their spectral energy distribution and estimated their physical parameters. Results. A total of 198 sources have been detected in all 5 Hi-GAL bands, 117 of which are associated with 24 μm emission and 87 of which are not associated with 24 μm emission. We called the former sources 24 μm-bright and the latter ones 24 μm-dark. The [70–160] color of the 24 μm-dark sources is smaller than that of the 24 μm-bright ones. The 24 μm-dark sources have lower Lbol and Lbol/Menv than the 24 μm-bright ones for similar Menv, which suggests that they are in an earlier evolutionary phase. The G29-SFR cloud is associated with 10 NVSS sources and with extended centimeter continuum emission well correlated with the 70 μm emission. Most of the NVSS sources appear to be early B or late O-type stars. The most massive and luminous Hi-GAL sources in the cloud are located close to the G29-UC region, which suggests that there is a privileged area for massive star formation toward the center of the G29-SFR cloud. Almost all the Hi-GAL sources have masses well above the Jeans mass but only 5% have masses above the virial mass, which indicates that most of the sources are stable against gravitational collapse. The sources with Menv > Mvirial and that should be undergoing collapse and forming stars are preferentially located at ≲4' of the G29-UC region, which is the most luminous source in the cloud. The overall SFE of the G29-SFR cloud ranges from 0.7 to 5%, and the SFR ranges from 0.001 to 0.008 M⊙ yr-1, consistent with the values estimated for Galactic Hii regions. The mass spectrum of the sources with masses above 300 M⊙, well above the completeness limit, can be well-fitted with a power law of slope α = 2.15 ± 0.30, consistent with the values obtained for the whole l = 30°, associated with high-mass star formation, and l = 59°, associated with low- to intermediate-mass star formation, Hi-GAL SDP fields. [ABSTRACT FROM AUTHOR]

Context. Stars form in dense, dusty clumps of molecular clouds, but little is known about their origin and evolution. In particular, the relationship between the mass distribution of these clumps (also known as the clump mass function or CMF) and the stellar initial mass function (IMF), is still poorly understood. Aims. To discern the "true" shape of the CMF and to better understand how the CMF may evolve toward the IMF, large samples of bona-fide pre- and proto-stellar clumps are required. The sensitive observations of the Herschel Space Observatory (HSO) are now allowing us to look at large clump populations in various clouds with different physical conditions. Methods. We analyze two fields in the Galactic plane mapped by HSO during its science demonstration phase (SDP), as part of the more complete and unbiased Herschel infrared GALactic Plane Survey (Hi-GAL). These fields underwent a source-extraction and flux-estimation pipeline, which allowed us to obtain a sample with thousands of clumps. Starless and proto-stellar clumps were separated using both color and positional criteria to find those coincident with MIPS 24 μm sources. We describe the probability density functions of the power-law and lognormal models that were used to fit the CMFs. For the lognormal model we applied several statistical techniques to the data and compared their results. Results. The CMFs of the two SDP fields show very similar shapes, but very different mass scales. This similarity is confirmed by the values of the best-fit parameters of either the power-law or lognormal model. The power-law model leads to almost identical CMF slopes, whereas the lognormal model shows that the CMFs have similar widths. Conclusions. The similar CMF shape but different mass scale represents an evidence that the overall process of star formation in the two regions is very different. When comparing with the IMF, we find that the width of the IMF is narrower than the measured widths of the CMF in the two SDP fields. This may suggest that an additional mass selection occurs in later stages of gravitational collapse. [ABSTRACT FROM AUTHOR]

We present a study of the star formation histories of the Lupus I, III, and IV clouds using the Herschel 70-500 μm maps obtained by the Herschel Gould Belt Survey Key Project. By combining the new Herschel data with the existing Spitzer catalog we obtained an unprecedented census of prestellar sources and young stellar objects in the Lupus clouds, which allowed us to study the overall star formation rate (SFR) and efficiency (SFE). The high SFE of Lupus III, its decreasing SFR, and its large number of pre-main sequence stars with respect to proto- and prestellar sources, suggest that Lupus III is the most evolved cloud, and after having experienced a major star formation event in the past, is now approaching the end of its current star-forming cycle. Lupus I is currently undergoing a large star formation event, apparent by the increasing SFR, the large number of prestellar objects with respect to more evolved objects, and the high percentage of material at high extinction (e.g., above AV ≈ 8mag). Also Lupus IV has an increasing SFR; however, the relative number of prestellar sources is much lower, suggesting that its star formation has not yet reached its peak. [ABSTRACT FROM AUTHOR]

Aims. The Herschel survey of the Galactic plane (Hi-GAL) provides a unique opportunity to study star formation over large areas of the sky and different environments in the Milky Way. We use the best-studied Hi-GAL fields to date, two 2° · 2° tiles centered on (ℓ, b) = (30°, 0°) and (ℓ, b) = (59°, 0°), to study the star formation activity in these regions of the sky using a large sample of well-selected young stellar objects (YSOs). Methods. We used the science demonstration phase Hi-GAL fields, where a tremendous effort has been made to identify the newly formed stars and to derive their properties as accurately as possible, e.g. distance, bolometric luminosity, envelope mass, and stage of evolution. We estimated the star formation rate (SFR) for these fields using the number of candidate YSOs and their average time scale to reach the zero age main sequence, and compared it with the rate estimated using their integrated luminosity at 70 μm, combined with an extragalactic star formation indicator. Results. We measure an SFR of (9.5 ± 4.3) × 10-4 M⊕/yr and (1.6 ± 0.7) × 10-4 M⊕/yr with the source counting method, in ℓ = 30° and ℓ = 59°, respectively. Results with the 70 μm estimator are (2.4 ± 0.4) × 10-4 M⊕/yr and (2.6 ± 1.1) × 10-6 M⊕/yr. Since the 70 μm indicator is derived from averaging extragalactic star forming complexes, we extrapolated of these values to the whole Milky Way and obtain SFRMW = (0.71 ± 0.13) M⊕/yr from ℓ = 30° and SFRMW = (0.10 ± 0.04) M⊕/yr from ℓ = 59°. The estimates in ℓ = 30° agree with the most recent results for Galactic star formation activity. Conclusions. The source-counting method gives results that are only valid for the particular region under consideration. In contrast, the construction of the IR indicator leads to results that can be extrapolated to the whole Galaxy. In particular, when it is applied to the ℓ = 30° field, it provides an SFR that is consistent with previous estimates, indicating that the characteristics of this field are very likely close to those of the star formation-dominated galaxies used for its derivation. Since the sky coverage is limited, this analysis will improve when the full Hi-GAL survey is available. It will cover the whole Galactic plane, sampling almost the totality of Galactic star forming complexes. By means of the candidate YSO-counting method, it will then be possible to calibrate an SFR Galactic indicator and to test the validity of the extragalactic estimators. [ABSTRACT FROM AUTHOR]

We report far-infrared Herschel observations obtained between 70 μm and 500 μm of two star-forming dusty condensations, [HKM99] B1-bS and [HKM99] B1-bN, in the B1 region of the Perseus star-forming cloud. In the western part of the Perseus cloud, B1-bS is the only source detected in all six PACS and SPIRE photometric bands, but it is not visible in the Spitzer map at 24 μm. B1-bN is clearly detected between 100 μm and 250 μm. We have fitted the spectral energy distributions of these sources to derive their physical properties, and find that a simple greybody model fails to reproduce the observed spectral energy distributions. At least a two-component model is required, consisting of a central source surrounded by a dusty envelope. The properties derived from the fit, however, suggest that the central source is not a Class 0 object. We then conclude that while B1-bS and B1-bN appear to be more evolved than a pre-stellar core, the best-fit models suggest that their central objects are younger than a Class 0 source. Hence, they may be good candidates to be examples of the first hydrostatic core phase. The projected distance between B1-bS and B1-bN is a few Jeans lengths. If their physical separation is close to this value, this pair would allow studying the mutual interactions between two forming stars at a very early stage of their evolution [ABSTRACT FROM AUTHOR]

Aims. As part of the Herschel guaranteed time key programme "HOBYS", we present the PACS and SPIRE photometric survey of the star-forming region Vela-C, one of the nearest sites of low-to-high-mass star formation in the Galactic plane. Our main objectives are to take a census of the cold sources and to derive their mass distribution down to a few solar masses. Methods. Vela-C was observed with PACS and SPIRE in parallel mode at five wavelengths between 70 μm and 500 μm over an area of about 3 square degrees. A photometric catalogue was extracted from the detections in each of the five bands, using a threshold of 5σ over the local background. Out of this catalogue we selected a robust sub-sample of 268 sources, of which ∼75% are cloud clumps (diameter between 0.05 pc and 0.13 pc) and 25% are cores (diameter between 0.025 pc and 0.05 pc). Their spectral energy distributions (SEDs) were fitted with a modified black body function. We classify 48 sources as protostellar, based on their detection at 70 μm or at shorther wavelengths, and 218 as starless, because of non-detections at 70 μm. For two other sources, we do not provide a secure classification, but suggest they are Class 0 protostars. Results. From the SED fitting we derived key physical parameters (i.e.mass, temperature, bolometric luminosity). Protostellar sources are in general warmer ([T] = 12.8K) and more compact ([diameter] = 0.040 pc) than starless sources ([T] = 10.3K, [diameter] = 0.067 pc). Both these findings can be ascribed to the presence of an internal source(s) of moderate heating, which also causes a temperature gradient and hence a more peaked intensity distribution. Moreover, the reduced dimensions of protostellar sources may indicate that they will not fragment further. A virial analysis of the starless sources gives an upper limit of 90% probability for the sources to be gravitationally bound and therefore prestellar in nature. A luminosity vs. mass diagram of the two populations shows that protostellar sources are in the early accretion phase, while prestellar sources populate a region of the diagram where mass accretion has not started yet. We fitted a power law N(log M) α M-1.1±0.2 to the linear portion of the mass distribution of prestellar sources. This is in between that typical of CO clumps and those of cores in nearby star-forming regions. We interpret this as a result of the inhomogeneity of our sample, which is composed of comparable fractions of clumps and cores. [ABSTRACT FROM AUTHOR]