Carina Nebula Complex Research Articles

Diffuse γ-ray emission around the massive star forming region of Carina Nebula Complex

ABSTRACT We report the Fermi Large Area Telescope (Fermi-LAT) detection of the γ-ray emission toward the massive star forming region of Carina Nebula Complex (CNC). Using the latest source catalogue and diffuse background models, we found that the GeV γ-ray emission in this region can be resolved into three different components. The GeV γ-ray emission from the central point source is considered to originate from the η Carina (η Car). We further found the diffuse GeV γ-ray emission around the CNC which can be modelled by two Gaussian discs with radii of 0.4○ (region A) and 0.75○ (region B), respectively. The GeV γ-ray emission from both the regions A and B have good spatial consistency with the derived molecular gas in projection on the sky. The GeV γ-ray emission of region A reveals a characteristic spectral shape of the pion-decay process, which indicates that the γ-rays are produced by the interactions of hadronic cosmic rays with ambient gas. The γ-rays spectrum of region B has a hard photon index of 2.12 ± 0.02, which is similar to other young massive star clusters. We argue that the diffuse GeV γ-ray emission in region A and region B likely originate from the interaction of accelerated protons in clusters with the ambient gas.

GaiaEDR3 distances of the young stellar clusters in the extended Carina Nebula complex

Context.The Carina Nebula complex (CNC) is one of the most massive and active star-forming regions in our Galaxy and it contains several large young star clusters. The distances of the individual clusters and their physical connection were poorly known up to now, with strongly discrepant results reported in the literature.Aims.We want to determine reliable distances of the young stellar clusters in the central Carina Nebula region (in particular, Tr 14, 15, and 16) and the prominent clusters NGC 3324 and NGC 3293 in the northwestern periphery of the CNC.Methods.We analyzed the parallaxes inGaiaEDR3 for a comprehensive sample of 237 spectroscopically identified OB stars, as well as for 9562 X-ray-selected young stars throughout the complex. We also performed an astrometric analysis to identify members of the young cluster vdBH 99, which is located in the foreground of the northwestern part of the Carina Nebula.Results.We find that the distances of the investigated clusters in the CNC are equal within ≤2%, and yield very consistent most likely mean distance values of 2.36−0.05+0.05kpc for the OB star sample and 2.34−0.06+0.05kpc for the sample of X-ray-selected young stars.Conclusions.Our results show that the clusters in the CNC constitute a coherent star-forming region, in particular with regard to NGC 3324 and NGC 3293 at the northwestern periphery, which are (within ≤2%) at the same distance as the central Carina Nebula. For the foreground cluster vdBH 99, we find a mean distance of 441−2+2pc and an age of ≃60 Myr. We quantified the contamination of X-ray-selected samples of Carina Nebula stars based on members of this foreground cluster.

Probing Polarization and the Role of Magnetic Fields in Cloud Destruction in the Keyhole Nebula

Abstract We present polarimetric observations of the Keyhole Nebula in the Carina Nebula Complex carried out using the Stratospheric Observatory for Infrared Astronomy. The Keyhole Nebula, located to the west of η Carinae, is believed to be disturbed by the stellar winds from the massive star. We observed the Keyhole Nebula at 89 μm wavelength with the HAWC+ instrument. The observations cover the entire Keyhole Nebula spanning 8′ by 5′ with central position R.A. = 10:44:43 and decl. = −59:38:04. The typical uncertainty of polarization measurement is less than 0.5% in the region with intensity above 5500 MJy sr−1. The polarization fraction has a mean value of 2.4% with a standard deviation of 1.6% in the region above this intensity, similar to values in other high-mass star-forming regions. The magnetic field orientation in the bar-shaped structure is similar to the large-scale magnetic field orientation. On the other hand, the magnetic field direction in the loop is not aligned with the large-scale magnetic fields but is tightly aligned with the loop itself. Analysis of the magnetic field angles and the gas turbulence suggests that the field strength is ∼70 μG in the loop. A simple comparison of the magnetic field tension to the ram pressure of η Carinae’s stellar wind suggests that the magnetic fields in the Keyhole Nebula are not strong enough to maintain the current structure against the impact of the stellar wind and that the role of the magnetic field in resisting stellar feedback in this region is limited.

Massive star formation in the Carina nebula complex and Gum 31. II. A cloud–cloud collision in Gum 31

Abstract We present the results of analyses of the 12CO (J = 1–0), 13CO (J = 1–0), and 12CO (J = 2–1) emission data toward Gum 31. Three molecular clouds separated in velocity were detected at −25, −20, and −10 km s−1. The velocity structure of the molecular clouds in Gum 31 cannot be interpreted as an expanding motion. Two of them, the −25 km s−1 cloud and the −20 km s−1 cloud, are likely to be associated with Gum 31, because their 12CO (J = 2–1)$/$12CO (J = 1–0) intensity ratios are high. We found that these two clouds show the observational signatures of cloud–cloud collisions (CCCs): a complementary spatial distribution and a V-shaped structure (bridge features) in the position–velocity diagram. In addition, their morphology and velocity structures are very similar to the numerical simulations conducted by the previous studies. We propose a scenario that the −25 km s−1 cloud and the −20 km s−1 cloud collided and triggered the formation of the massive star system HD 92206 in Gum 31. This scenario can explain the offset of the stars from the center and the morphology of Gum 31 simultaneously. The timescale of the collision was estimated to be ∼1 Myr by using the ratio between the path length of the collision and the assumed velocity separation. This is consistent with that of the CCCs in the Carina Nebula Complex in our previous study.

Small-scale star formation as revealed by VVVX galactic cluster candidates

ABSTRACT We report a search and analysis of obscured cluster candidates in the ‘VISTA Variables in the Via Lactea eXtended (VVVX)’ ESO Public Survey area encompassing the region between 229${_{.}^{\circ}}$4 < l < 295${_{.}^{\circ}}$2 and −4${_{.}^{\circ}}$3 < b < 4${_{.}^{\circ}}$4 of the southern Galactic disc. We discover and propose 88 new clusters. We improve the completeness of the embedded cluster population in this region, adding small size (linear diameters of 0.2–1.4 pc) and relatively far objects (heliocentric distance between 2 and 4 kpc) to existing catalogues. Nine candidates are proposed to be older open cluster candidates. Three of them (VVVX CL 204, CL 207, CL 208) have sufficient numbers of well-resolved stellar members to allow us to determine some basic cluster parameters. We confirm their nature as older, low-mass open clusters. Photometric analysis of 15 known clusters shows that they have ages above 20 Myr, and masses below 2000 M⊙: in general, their proper motions follow the motion of the disc. We outline some groups of clusters, most probably formed within the same dust complex. Broadly, our candidates follow the network of filamentary structure in the remaining dust. Thus, in this part of the southern disc of the Galaxy, we have found recent star formation, producing small size and young clusters, in addition to the well-known, massive young clusters, including NGC 3603, Westerlund 2, and the Carina Nebula Complex.

Massive star formation in the Carina nebula complex and Gum 31. I. the Carina nebula complex

Abstract Herein, we present results from observations of the 12CO (J = 1–0), 13CO (J = 1–0), and 12CO (J = 2–1) emission lines toward the Carina nebula complex (CNC) obtained with the Mopra and NANTEN2 telescopes. We focused on massive-star-forming regions associated with the CNC including the three star clusters Tr 14, Tr 15, and Tr 16, and the isolated WR-star HD 92740. We found that the molecular clouds in the CNC are separated into mainly four clouds at velocities −27, −20, −14, and −8 km s−1. Their masses are 0.7 × 104 M⊙, 5.0 × 104 M⊙, 1.6 × 104 M⊙, and 0.7 × 104 M⊙, respectively. Most are likely associated with the star clusters, because of their high 12CO (J = 2–1)/12CO (J = 1–0) intensity ratios and their correspondence to the Spitzer 8 μm distributions. In addition, these clouds show the observational signatures of cloud–cloud collisions. In particular, there is a V-shaped structure in the position–velocity diagram and a complementary spatial distribution between the −20 km s−1 cloud and the −14 km s−1 cloud. Furthermore, we found that SiO emission, which is a tracer of a shocked molecular gas, is enhanced between the colliding clouds by using ALMA archive data. Based on these observational signatures, we propose a scenario wherein the formation of massive stars in the clusters was triggered by a collision between the two clouds. By using the path length of the collision and the assumed velocity separation, we estimate the timescale of the collision to be ∼1 Myr. This is comparable to the ages of the clusters estimated in previous studies.

The Duration of Star Formation in Galactic Giant Molecular Clouds. I. The Great Nebula in Carina

Abstract We present a novel infrared spectral energy distribution (SED) modeling methodology that uses likelihood-based weighting of the model fitting results to construct probabilistic Hertzsprung–Russell diagrams (pHRD) for X-ray-identified, intermediate-mass (2–8 M ⊙), pre-main-sequence young stellar populations. This methodology is designed specifically for application to young stellar populations suffering strong, differential extinction (ΔA V > 10 mag), typical of Galactic massive star-forming regions. We pilot this technique in the Carina Nebula Complex (CNC) by modeling the 1–8 μm SEDs of 2269 likely stellar members that exhibit no excess emission from circumstellar dust disks at 4.5 μm or shorter wavelengths. A subset of ∼100 intermediate-mass stars in the lightly obscured Trumpler 14 and 16 clusters have available spectroscopic T eff, measured from the Gaia-ESO survey. We correctly identify the stellar temperature in 85% of cases, and the aggregate pHRD for all sources returns the same peak in the stellar age distribution as obtained using the spectroscopic T eff. The SED model parameter distributions of stellar mass and evolutionary age reveal significant variation in the duration of star formation among four large-scale stellar overdensities within the CNC and a large distributed stellar population. Star formation began ∼10 Myr ago and continues to the present day, with the star formation rate peaking ≲3 Myr ago when the massive Trumpler 14 and 16 clusters formed. We make public the set of 100,000 SED models generated from standard pre-main-sequence evolutionary tracks and our custom software package for generating pHRDs and mass–age distributions from the SED fitting results.

Probing ISM Structure in Trumpler 14 and Carina I Using the Stratospheric Terahertz Observatory 2

Abstract We present observations of the Trumpler 14/Carina I region carried out using the Stratospheric Terahertz Observatory 2. The Trumpler 14/Carina I region is in the western part of the Carina Nebula Complex (CNC), which is one of the most extreme star-forming regions in the Milky Way. We observed Trumpler 14/Carina I in the 158 μm transition of [C ii] with a spatial resolution of 48″ and a velocity resolution of 0.17 km s−1. The observations cover a 0.°25 by 0.°28 area with central position l = 297.°34, b = −0.°60. The kinematics show that bright [C ii] structures are spatially and spectrally correlated with the surfaces of CO clouds, tracing the photodissociation region (PDR) and ionization front of each molecular cloud. Along seven lines of sight (LOSs) that traverse Tr 14 into the dark ridge to the southwest, we find that the [C ii] luminosity from the H ii region is 3.7 times that from the PDR. In the same LOS, we find in the PDRs an average ratio of 1 : 4.1 : 5.6 for the mass in atomic gas : dark CO gas : molecular gas traced by CO. Comparing multiple gas tracers, including H i 21 cm, [C ii], CO, and radio recombination lines, we find that the H ii regions of the CNC are well described as H ii regions with one side freely expanding toward us, consistent with the Champagne model of ionized gas evolution. The dispersal of the GMC in this region is dominated by EUV photoevaporation; the dispersal timescale is 20–30 Myr.

On the diagnostic power of FIR/sub-mm SED fitting in massive galactic molecular clumps

We used FIR and submillimeter continuum data from Herschel and the Atacama Pathfinder EXperiment (APEX) to fit pixel-by-pixel modified Planck SEDs to prestellar and protostellar clumps in the Census of High- and Medium-mass Protostars (CHaMP) ($280^{\circ}<\ell<300^{\circ}$, $-4^{\circ}<b<+2^{\circ}$). We present maps of dust temperature ($T_{\text{d}}$) and H$_2$ column density (\ncol) for molecular clumps in the Carina Nebula complex (Regions 9 through 11), and surrounding RCW 64 (Region 26). We compare the column densities of CO and H$_2$ to chart regional variations in their correspondence, and derive maps of the CO abundance. We find the CO abundance varies by an order of magnitude or more across each region, averaging a few$\times$10$^{-5}$ CO per H$_2$, and that the CO abundance distribution across each clump is correlated in both form and magnitude with environmental conditions, especially $T_{\text{d}}$. This demonstrates that no single CO abundance suffices to convert from $N_{\text{CO}}$ to \ncol, even within a single molecular cloud. We also find that $L/M$ traces $T_{\text{d}}$ almost exclusively, and therefore is not an independent star formation tracer, but minima in $T_{\text{d}}$ almost universally coincide with maxima in \ncol, implying that cooling and density enhancement must be simultaneous steps in prestellar clump evolution. Finally, based on generalized histogram N-PDFs of clump-scale (1-5 pc) and cloud-scale ($\gtrsim10$ pc) samples, we could only obtain dual log-normal and power-law fits to $\sim10\%$ of the clumps. The physical parameters derived from these fits approach theoretical expectations, but have largely unknown uncertainties, so we advise treating the results of N-PDF fitting with caution.

Chandra X-ray observation of the young stellar cluster NGC 3293 in the Carina Nebula Complex

Context. NGC 3293 is a young stellar cluster at the northwestern periphery of the Carina Nebula Complex that has remained poorly explored until now.

The Carina Nebula and Gum 31 molecular complex – II. The distribution of the atomic gas revealed in unprecedented detail

We report high spatial resolution observations of the H i 21cm line in the Carina Nebula and the Gum 31 region obtained with the Australia Telescope Compact Array. The observations covered ∼12 |$\deg ^2$| centred on l = 287|$_{.}^{\circ}$|5, b = −1°, achieving an angular resolution of ∼35 arcsec. The H i map revealed complex filamentary structures across a wide range of velocities. Several ‘bubbles’ are clearly identified in the Carina Nebula complex, produced by the impact of the massive star clusters located in this region. An H i absorption profile obtained towards the strong extragalactic radio source PMN J1032−5917 showed the distribution of the cold component of the atomic gas along the Galactic disc, with the Sagittarius–Carina and Perseus spiral arms clearly distinguishable. Preliminary calculations of the optical depth and spin temperatures of the cold atomic gas show that the H i line is opaque (τ ≳ 2) at several velocities in the Sagittarius–Carina spiral arm. The spin temperature is ∼100 K in the regions with the highest optical depth, although this value might be lower for the saturated components. The atomic mass budget of Gum 31 is ∼35 per cent of the total gas mass. H i self-absorption features have molecular counterparts and good spatial correlation with the regions of cold dust as traced by the infrared maps. We suggest that in Gum 31 regions of cold temperature and high density are where the atomic to molecular gas-phase transition is likely to be occurring.

GRAVITY Spectro-interferometric Study of the Massive Multiple Stellar System HD 93206 A

Abstract Characterization of the dynamics of massive star systems and the astrophysical properties of the interacting components are a prerequisite for understanding their formation and evolution. Optical interferometry at milliarcsecond resolution is a key observing technique for resolving high-mass multiple compact systems. Here, we report on Very Large Telescope Interferometer/GRAVITY, Magellan/Folded-port InfraRed Echellette, and MPG2.2 m/FEROS observations of the late-O/early-B type system HD 93206 A, which is a member of the massive cluster Collinder 228 in the Carina nebula complex. With a total mass of about , it is one of the most compact massive quadruple systems known. In addition to measuring the separation and position angle of the outer binary Aa–Ac, we observe Brγ and He i variability in phase with the orbital motion of the two inner binaries. From the differential phase ( ) analysis, we conclude that the Brγ emission arises from the interaction regions within the components of the individual binaries, which is consistent with previous models for the X-ray emission of the system based on wind–wind interaction. With an average 3σ deviation of , we establish an upper limit of p ∼ 0.157 mas (0.35 au) for the size of the Brγ line-emitting region. Future interferometric observations with GRAVITY using the 8 m Unit Telescopes will allow us to constrain the line-emitting regions down to angular sizes of 20 μas (0.05 au at the distance of the Carina nebula).

The VISTA Carina Nebula Survey

We performed a deep wide-field (6.76 sq. deg) near-infrared survey with the VISTA telescope that covers the entire extent of the Carina nebula complex (CNC). The point-source catalog created from these data contains around four million individual objects down to masses of 0.1 M⊙. We present a statistical study of the large-scale spatial distribution and an investigation of the clustering properties of infrared-excesses objects, which are used to trace disk-bearing young stellar objects (YSOs). A selection based on a near-infrared (J−H) versus (H−Ks) color–color diagram shows an almost uniform distribution over the entire observed area. We interpret this as a result of the very high degree of background contamination that arises from the Carina Nebula’s location close to the Galactic plane. Complementing the VISTA near-infrared catalog with Spitzer IRAC mid-infrared photometry improves the situation of the background contamination considerably. We find that a (J−H) versus (Ks− [4.5]) color–color diagram is well suited to tracing the population of YSO-candidates (cYSOs) by their infrared excess. We identify 8781 sources with strong infrared excess, which we consider as cYSOs. This sample is used to investigate the spatial distribution of the cYSOs with a nearest-neighbor analysis. The surface density distribution of cYSOs agrees well with the shape of the clouds as seen in our Herschel far-infrared survey. The strong decline in the surface density of excess sources outside the area of the clouds supports the hypothesis that our excess-selected sample consists predominantly of cYSOs with a low level of background contamination. This analysis allows us to identify 14 groups of cYSOs outside the central area.Our results suggest that the total population of cYSOs in the CNC comprises about 164 000 objects, with a substantial fraction (~35%) located in the northern, still not well studied parts. Our cluster analysis suggests that roughly half of the cYSOs constitute a non-clustered, dispersed population.

The VISTA Carina Nebula Survey

Context. The Carina Nebula is one of the most massive and active star-forming regions in our Galaxy and has been studied with numerous multiwavelength observations in the past five years. However, most of these studies were restricted to the inner parts (≲1 square-degree) of the nebula, and thus covered only a small fraction of the whole cloud complex. Aims. Our aim was to conduct a near-infrared survey that covers the full spatial extent (~5 square-degrees) of the Carina Nebula complex and is sensitive enough to detect all associated young stars through extinctions of up to A V ≈ 6 mag. Methods. We used the 4m Visible and Infrared Survey Telescope for Astronomy (VISTA) of ESO to map an area of 6.7 square-degrees around the Carina Nebula in the near-infrared J -, H -, K s -bands. Results. The analysis of our VISTA data revealed 4 840 807 individual near-infrared sources, 3 951 580 of which are detected in at least two bands. The faintest S /N ≥ 3 detections have magnitudes of J ≈ 21.2, H ≈ 19.9, and K s ≈ 19.3. For objects at the distance of the Carina Nebula (2.3 kpc), our catalog is estimated to be complete down to stellar masses of ≈0.1 M ⊙ for young stars with extinctions of A V ≈ 5 mag; for regions in the brightest parts of the central nebula with particularly strong diffuse emission, the completeness limit is at slightly higher stellar masses. We describe the photometric calibration, the characteristics, and the quality of these data. VISTA images of several newly detected or yet rarely studied clusters in the outer parts of the Carina Nebula complex are presented. Finally, a list of stars with high proper motions that were discovered in our analysis is provided in an appendix. Conclusions. Our catalog represents by far the most comprehensive deep near-infrared catalog of the Carina Nebula complex. It provides a new basis for spatially complete investigations of the young stellar population in this important star-forming complex.

ChandraX-ray observation of the H ii region Gum 31 in the Carina nebula complex

(abridged) We used the Chandra observatory to perform a deep (70 ksec) X-ray observation of the Gum 31 region and detected 679 X-ray point sources. This extends and complements the X-ray survey of the central Carina nebula regions performed in the Chandra Carina Complex Project. Using deep near-infrared images from our recent VISTA survey of the Carina nebula complex, our Spitzer point-source catalog, and optical archive data, we identify counterparts for 75% of these X-ray sources. Their spatial distribution shows two major concentrations, the central cluster NGC 3324 and a partly embedded cluster in the southern rim of the HII region, but majority of X-ray sources constitute a rather homogeneously distributed population of young stars. Our color-magnitude diagram analysis suggests ages of ~1-2 Myr for the two clusters, whereas the distributed population shows a wider age range up to ~10 Myr. We also identify previously unknown companions to two of the three O-type members of NGC 3324 and detect diffuse X-ray emission in the region. Our results suggests that the observed region contains about 4000 young stars in total. The distributed population is probably part of the widely distributed population of ~ 1-10 Myr old stars, that was identified in the CCCP area. This implies that the global stellar configuration of the Carina nebula complex is a very extended stellar association, in which the (optically prominent) clusters contain only a minority of the stellar population.

Discovering young stars in the Gum 31 region with infrared observations

Context. The Gum 31 bubble containing the stellar cluster NGC 3324 is a poorly-studied young region close to the Carina Nebula. Aims. We are aiming to characterise the young stellar and protostellar population in and around Gum 31 and to investigate the star-formation process in this region. Methods. We identify candidate young stellar objects from Spitzer, WISE, and Herschel data. Combining these, we analyse the spectral energy distributions of the candidate young stellar objects. With density and temperature maps obtained from Herschel data and comparisons to a 'collect and collapse' scenario for the region we are able to further constrain the characteristics of the region as a whole. Results. 661 candidate young stellar objects are found from WISE data, 91 protostar candidates are detected through Herschel observations in a 1.0 deg x 1.1 deg area. Most of these objects are found in small clusters or are well aligned with the H II bubble. We also identify the sources of Herbig-Haro jets. The infrared morphology of the region suggests that it is part of the larger Carina Nebula complex. Conclusions. The location of the candidate young stellar objects in the rim of the H II bubble is suggestive of their being triggered by a 'collect and collapse' scenario, which agrees well with the observed parameters of the region. Some candidate young stellar objects are found in the heads of pillars, which points towards radiative triggering of star formation. Thus, we find evidence that in the region different mechanisms of triggered star formation are at work. Correcting the number of candidate young stellar objects for contamination we find ~ 600 young stellar objects in Gum 31 above our completeness limit of about 1 M_sol. Extrapolating the intital mass function down to 0.1 M_sol, we estimate a total population of ~ 5000 young stars for the region.

The clump mass function of the dense clouds in the Carina nebula complex

We want to characterize the properties of the cold dust clumps in the Carina Nebula Complex (CNC), which shows a very high level of massive star feedback. We derive the Clump Mass Function (ClMF), explore the reliability of different clump extraction algorithms, and investigate the influence of the temperatures within the clouds on the resulting shape of the ClMF. We analyze a 1.25x1.25 deg^2 wide-field sub-mm map obtained with LABOCA (APEX), which provides the first spatially complete survey of the clouds in the CNC. We use the three clump-finding algorithms CLUMPFIND (CF), GAUSSCLUMPS (GC) and SExtractor (SE) to identify individual clumps and determine their total fluxes. In addition to assuming a common `typical' temperature for all clouds, we also employ an empirical relation between cloud column densities and temperature to determine an estimate of the individual clump temperatures, and use this to determine individual clump masses. While the ClMF based on the CF extraction is very well described by a power-law, the ClMFs based on GC and SE are better represented by a log-normal distribution. We also find that the use of individual clump temperatures leads to a shallower ClMF slope than the assumption of a common temperature (e.g. 20 K) of all clumps. The power-law of dN/dM \propto M^-1.95 we find for the CF sample is in good agreement with ClMF slopes found in previous studies of other regions. The dependence of the ClMF shape (power-law vs. log-normal distribution) on the employed extraction method suggests that observational determinations of the ClMF shape yields only very limited information about the true structure of the cloud. Interpretations of log-normal ClMF shape as a signature of turbulent pre-stellar clouds vs. power-law ClMFs as a signature of star-forming clouds may be taken with caution for a single extraction algorithm without additional information.

Herschelfar-infrared observations of the Carina Nebula complex

The Carina Nebula represents one of the largest and most active star forming regions known in our Galaxy with numerous very massive stars.Our recently obtained Herschel PACS & SPIRE far-infrared maps cover the full area (about 8.7 deg^2) of the Carina Nebula complex and reveal the population of deeply embedded young stellar objects, most of which are not yet visible in the mid- or near-infrared.We study the properties of the 642 objects that are independently detected as point-like sources in at least two of the five Herschel bands.For those objects that can be identified with apparently single Spitzer counterparts, we use radiative transfer models to derive information about the basic stellar and circumstellar parameters.We find that about 75% of the Herschel-detected YSOs are Class 0 protostars.The luminosities of the Herschel-detected YSOs with SED fits are restricted to values of <=5400 Lsun, their masses (estimated from the radiative transfer modeling) range from about 1 Msun to 10 Msun.Taking the observational limits into account and extrapolating the observed number of Herschel-detected protostars over the IMF suggest that the star formation rate of the CNC is about 0.017 Msun/yr.The spatial distribution of the Herschel YSO candidates is highly inhomogeneous and does not follow the distribution of cloud mass.Most Herschel YSO candidates are found at the irradiated edges of clouds and pillars.This provides support to the picture that the formation of this latest stellar generation is triggered by the advancing ionization fronts.The currently ongoing star formation process forms only low-mass and intermediate-mass stars, but no massive stars.The far-infrared fluxes of the famous object EtaCar are about a factor of two lower than expected from observations with the ISO obtained 15 years ago; this may be due to dynamical changes in the circumstellar dust in the Homunculus Nebula.

Herschelfar-infrared observations of the Carina Nebula complex

The Carina Nebula represents one of the most massive galactic star forming regions and displays a high level of massive star feedback. We used SPIRE and PACS onboard of Herschel to map the full spatial extent of the clouds in the Carina Nebula complex at wavelengths between 70 and 500 micrometer. We determine color temperatures and column densities of the clouds in the complex. Our Herschel maps show that the clouds have a very complex and filamentary structure that is dominated by the radiation and wind feedback from the massive stars. In most locations, the column density of the clouds is N_H < 2x10^22 cm^-2; denser cloud structures are restricted to just a few locations. We find a clear large scale temperature gradient from 35-40 K in the central region to <20 K at the periphery and in the densest parts of individual pillars. The total mass of the clouds seen by Herschel in the central (1 deg radius) region is ~656000 M_sun. A simple radiative transfer model for the global spectral energy distribution suggests that the total mass of all the gas (including a warmer component that is not well traced by Herschel) is <=890000 M_sun. Despite the strong feedback from numerous massive stars that is going on since several million years, there are still several 10000 M_sun of cool cloud material present at column-densities sufficient for further star formation. Comparison of our total gas mass estimates to molecular cloud masses derived from CO line mapping suggests that as much as about 75% of all the gas is in atomic rather than molecular form.

Jet-driving protostars identified from infrared observations of the Carina Nebula complex

Aims: Jets are excellent signposts for very young embedded protostars, so we want to identify jet-driving protostars as a tracer of the currently forming generation of stars in the Carina Nebula, which is one of the most massive galactic star-forming regions and which is characterised by particularly high levels of massive-star feedback on the surrounding clouds. Methods: We used archive data to construct large (> 2 deg x 2 deg) Spitzer IRAC mosaics of the Carina Nebula and performed a spatially complete search for objects with excesses in the 4.5 micron band, typical of shock-excited molecular hydrogen emission. We also identified the mid-infrared point sources that are the likely drivers of previously discovered Herbig-Haro jets and molecular hydrogen emission line objects. We combined the Spitzer photometry with our recent Herschel far-infrared data to construct the spectral energy distributions, and used the Robitaille radiative-transfer modelling tool to infer the properties of the objects. Results: The radiative-transfer modelling suggests that the jet sources are protostars with masses between ~1 M_sol and ~10 M_sol that are surrounded by circumstellar disks and embedded in circumstellar envelopes. Conclusions: The estimated protostar masses < 10 M_sol suggest that the current star-formation activity in the Carina Nebula is restricted to low- and intermediate-mass stars. More optical than infrared jets can be observed, indicating that star formation predominantly takes place close to the surfaces of clouds.