Carina Nebula Research Articles

Diffuse X-Ray Emission from the Carina Nebula Observed with Suzaku

A number of giant HII regions are associated with soft diffuse X-ray emission. Among these, the Carina nebula possesses the brightest soft diffuse emission. The required plasma temperature and thermal energy can be produced by collisions or termination of fast winds from main-sequence or embedded young O stars, but the extended emission is often observed from regions apart from massive stellar clusters. The origin of the X-ray emission is unknown. The XIS CCD camera onboard Suzaku has the best spectral resolution for extended soft sources so far, and is therefore capable of measuring key emission lines in the soft band. Suzaku observed the core and the eastern side of the Carina nebula (Car-D1) in 2005 Aug and 2006 June, respectively. Spectra of the south part of the core and Car-D1 similarly showed strong L-shell lines of iron ions and K-shell lines of silicon ions, while in the north of the core these lines were much weaker. Fitting the spectra with an absorbed thin-thermal plasma model showed kT~0.2, 0.6 keV and NH~1-2e21 cm-2 with a factor of 2-3 abundance variation in oxygen, magnesium, silicon and iron. The plasma might originate from an old supernova, or a super shell of multiple supernovae.

Predicted radio-continuum emission from the little Homunculus of the Carinae nebula

In this paper, we compute theoretically the flux density and the spectral index of the free-free radiation at radio wavelengths produced by shocks in the inner bipolar emission nebula called the little Homunculus around the star η Carinae. The little Homunculus is believed to have formed as a result of the minor eruption suffered by the star in the 1890s. In our model, we consider a simplified interacting stellar wind scenario where the post-outburst η Carinae wind collides with the eruptive outflow (both assumed to be bipolar with conical symmetry). As a result of the interaction, shock-wave structures are formed and generate the development of two polar caps moving in opposite directions. After ∼100 yr (i.e. at present times), the polar caps are located ±2.3 arcsec on each side of the star, and remain embedded within the larger bipolar Homunculus that extends from -8 to +8 arcsec along its major axis. Using observational estimates of the characteristics of the eruptive event of the 1890s, and of the ambient wind powered by η Carinae in the decades after the eruption ended, we study the evolution of the polar caps formed as a result of a sudden increase in the wind velocity and an instantaneous drop in the mass-loss rate (just after the eruption) at the injection radius. We found that the little Homunculus emits continuum radiation that can be detected at radio frequencies and that indeed represents an important contribution to the total free-free emission detected from the η Carinae nebula.

Results of SPARO 2003: Mapping Magnetic Fields in Giant Molecular Clouds

We present results from the Austral Winter 2003 observing campaign of SPARO, a 450 μm polarimeter used with a 2 m telescope at the South Pole. We mapped large-scale magnetic fields in four GMCs in the Galactic disk: NGC 6334, the Carina Nebula, G333.6-0.2, and G331.5-0.1. We find a statistically significant correlation of the inferred field directions with the orientation of the Galactic plane. Specifically, three of the four GMCs (NGC 6334 is the exception) have mean field directions that are within 15° of the plane. The simplest interpretation is that the field direction tends to be preserved during the process of GMC formation. We have also carried out an analysis of published optical polarimetry data. For the closest of the SPARO GMCs, NGC 6334, we can compare the field direction in the cloud as measured by SPARO with the field direction in a larger region surrounding the cloud, as determined from optical polarimetry. For purposes of comparison, we also use optical polarimetry to determine field directions for 9-10 other regions of similar size. We find that the region surrounding NGC 6334 is an outlier in the distribution of field directions determined from optical polarimetry, just as the NGC 6334 cloud is an outlier in the distribution of cloud field directions determined by SPARO. In both cases the field direction corresponding to NGC 6334 is rotated away from the direction of the plane by a large angle. This finding is consistent with our suggestion that field direction tends to be preserved during GMC formation. Finally, by comparing the disorder in our magnetic field maps with the disorder seen in magnetic field maps derived from MHD turbulence simulations, we conclude that the magnetic energy density in our clouds is comparable to the turbulent energy density.

Diffuse X-ray emission from the Carina Nebula observed with Suzaku

AbstractThe Carina Nebula possesses the brightest soft diffuse X-ray emission among the Galactic giant HII regions, but the origin has not been known yet. The XIS1 back-illuminated CCD camera onboard the Suzaku X-ray observatory has the best spectral resolution for extended soft sources so far, and is therefore capable of measuring these key emission lines in the soft diffuse plasma. Suzaku observed the Carina nebula on 2005 Aug. 29. The XIS1 spectra of the Carina nebula clearly showed spatial variations in emission line strengths. In the south, the spectrum showed strong L-shell lines of iron ions and K-shell lines of silicon ions, while in the north these lines were much weaker. Fitting the spectra with an absorbed thin-thermal plasma model with kT ~ 0.2, 0.6 keV and NH ~ −2 × 1021 cm−2 showed that the silicon and iron abundance is about 2–3 times higher in the south than in the north. Because of its large size (~40 pc), the diffuse emission in the Carina nebula might have been produced by an old supernova, or a super shell produced by multiple supernovae.

Triggered star formation in OB associations

AbstractWe present causal and positional evidence of triggered star formation in bright-rimmed clouds in OB associations, e.g., Ori OB1, and Lac OB1, by photoionization. The triggering process is seen also on a much larger scale in the Orion-Monoceros Complex by the Orion-Eridanus Superbubble. We also show how the positioning of young stellar groups surrounding the H II region associated with Trumpler 16 in Carina Nebula supports the triggering process of star formation by the collect-and-collapse scenario.

Optical spectroscopy of X-Mega targets in the Carina nebula - VI. FO 15: a new O-type double-lined eclipsing binary

We report the discovery of a new O-type double-lined spectroscopic binary with a short orbital period of 1.4 d. We find the primary component of this binary, FO 15, to have an approximate spectral type 05.5Vz, i.e. a zero-age main-sequence (ZAMS) star. The secondary appears to be of spectral type 09.5V. We have performed a numerical model fit to the public All Sky Automated Survey photometry, which shows that FO 15 is also an eclipsing binary. We find an orbital inclination of ∼80°. From a simultaneous light curve and radial velocity solution, we find the masses and radii of the two components to be 30 ± 1 and 16 ± 1M ⊙ and 7.5 ± 0.5 and 5.3 ± 0.5 R ⊙ . These radii, and hence also the luminosities, are smaller than those of normal O-type stars, but similar to recently bom ZAMS O-type stars. The absolute magnitudes derived from our analysis locate FO 15 at the same distance as η Carinae. From Chandra and XMM X-ray images, we also find that there are two close X-ray sources: one coincident with FO 15 and the other one without optical counterpart. The latter seems to be a highly variable source, presumably due to a pre-main-sequence stellar neighbour of FO 15.

A census of the Carina Nebula -- I. Cumulative energy input from massive stars

The Carina Nebula (NGC 3372) is our richest nearby laboratory in which to study feedback through ultraviolet radiation and stellar winds from very massive stars during the formation of an OB association, at an early phase in the evolution of the surrounding proto-superbubble before supernova explosions have influenced the environment. This feedback is triggering successive generations of new star formation around the periphery of the nebula, while simultaneously evaporating the gas and dust reservoirs out of which young stars are trying to accrete material. This paper takes inventory of the combined effect from all the known massive stars that power the Carina Nebula through their total ionizing flux and integrated mechanical energy from their stellar winds. Carina is close enough and accessible enough that spectral types for individual stars are available, and many close binary and multiple systems have recently been spatially resolved, so that one can simply add them. Adopting values from the literature for corresponding spectral types, the present-day total ionizing photon luminosity produced by the 65 O stars and three WNL stars in Carina is Q H ≃ 10 51 s -1 , the total bolometric luminosity of all stars earlier than B2 is 2.5 x 10 7 L ⊙ , and the total mechanical luminosity of stellar winds is L SW ≃ 10 5 L ⊙ . The total Q H was about 25 per cent higher when η Carinae was on the main sequence, before it and its companion were surrounded by its obscuring dust shell; for the first 3 Myr, the net ionizing flux of the 70 O stars in Carina was about 150 times greater than in the Orion Nebula. About 400-500 M ⊙ has been contributed to the H II region by stellar wind mass-loss during the past 3 Myr. Values for Q H and Lsw are also given for the individual clusters Trl4, 15 and 16, and BolO and 11, which are more relevant on smaller spatial scales than the total values for the whole nebula.

Imaging study of NGC 3372, the Carina nebula -- II. Evidence of activity in the complex Trumpler 14/Car I photodissociation region

We present the results of an imaging survey, from the optical to the mid-infrared, of the dark cloud associated with Car I, a dense cloud that is subject to an intense ultraviolet radiation field from the rich stellar cluster Trumpler 14. New ground-based broad- and narrowband near-infrared and narrow-band optical images are analysed in combination with archived Spitzer/InfraRed Array Camera (IRAC) images to study this photodissociation region (PDR) and the triggering of a new generation of stars within the cloud, particularly close to its edges. Evidence is given of a clumpy morphology of the dense cloud. The ionization/dissociation front is delineated at the edges of these clumps. The existence of a number of embedded lowto intermediate-mass pre-main-sequence objects is confirmed by their considerable infrared excesses arising from discs and/or detectable X-ray emission. Most of the young stellar objects (YSOs) are located on or just behind ionization fronts, though a few are also outside the cloud. The infrared properties of the YSOs are discussed. Two Class I objects stand out, one of them is an FU Orionis system candidate that had an outburst of more than 3 mag in K between 1993 and 2003, with further evidence that it occurred in the 2000‐02 period. Molecular hydrogen line filamentary emission behind the Balmer and Brackett lines along the ionization front is seen delineating the edges of the dense cloud. This emission is also seen in all IRAC images. The diffuse, filamentary emission is very similar in all four 3.6, 4.5, 5.8 and 8 μm bands, though there seem to be subtle differences. Across a bright section of the ionization/dissociation front, we found that, within the observational uncertainties, the maximum emission in all four IRAC channels coincides with that of H2 2.12 μm. The western, embedded, dissociation front close to the CO peak (Car I-W) is seen delineated by a bright, long bar of emission in the 3‐12 μm images, in the Midcourse Space Experiment bands A and C and also in radio continuum and hydrogen line emission. These occur in the vicinity of a region of previously reported strong [C I], [C II] and [O I] emission, tracers of PDRs. A few bright, compact knots of H2 emission, some possibly associated with [S II] emission, are found within the cloud. These may be shock-excited.

Evidence for colliding winds in from XMM-Newton observations of X-ray variability

The Wolf-Rayet star WR 25 in the Carina Nebula is a surprisingly bright X-ray source, and amongst the brightest WR stars in X-rays. It is a suspected binary star, though its binary nature has been a matter of controversy. We report here observations of WR 25 from the XMM-Newton archive which showed an increase in X-ray luminosity of more than a factor of two. The X-ray absorption also increased. Such a large change in X-ray output is unknown in single massive stars, though large changes in X-ray brightness are seen in binaries. The most likely explanation of the observed X-ray variability is as a result of colliding-wind emission in a moderately eccentric binary with a period of about 4 years. The next periastron passage is expected in 2007. The X-ray spectrum is similar to that of the archetype colliding-wind binary WR 140.

The [Oiii] Veil: Astropause of η Carinae's Wind?

We present narrowband images of η Carinae in the light of [O III] λ5007 obtained with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2, as well as a ground-based image in the same emission line with a larger field of view. These images show a thin veil of [O III] emission around η Car and its ejecta, confirming the existence of an oxygen-bearing cocoon inferred from spectra. This [O III] veil may be the remnant of the preoutburst wind of η Car, and its outer edge probably marks the interface where η Car's ejecta meet the stellar wind of the nearby O4 V((f)) star HD 303308 or other ambient material in the Carina Nebula; i.e., it marks the astropause in η Car's wind. This veil is part of a more extensive [O III] shell that appears to be shaped and ionized by HD 303308. A pair of HST images with a 10 yr baseline shows no significant proper motion, limiting the expansion speed away from η Car to 12 ± 13 km s-1, or an expansion age of a few times 104 yr. Thus, this is probably the decelerated preoutburst luminous blue variable wind of η Car. The [O III] morphology is very different from that seen in [N II], which traces younger dense knots of CNO-processed material; this represents a dramatic shift in the chemical makeup of material recently ejected by η Car. This change in the chemical abundances of the ejecta may have resulted from the sudden removal of the star's outer envelope during η Car's 19th century outburst or an earlier but similar event.

A Survey of N iv and O iv Features near 3400 Å in O2–O5 Spectra

ABSTRACTWe have conducted a survey of little‐known N iv and O iv multiplets near 3400 Å in an extensive sample of well‐classified, very early O‐type spectra. The initial motivation was to search for additional useful classification criteria for these types, but an unexpected result is the high sensitivity of these features to evolutionary CNO processing. We have found a useful discriminant between O2 and later types in the relative strengths of the O iv multiplets, one of which is subject to selective emission in the hottest spectra; the overall strengths of these lines also decrease between spectral types O4 and O5. More remarkable, however, are the variations in the N/O ratios among both individual stars and clusters. For instance, several O4 If+ spectra have very large ratios, while main‐sequence stars in the Carina Nebula generally have smaller values than others of the same spectral types in other regions. These effects correspond to different degrees of mixing of processed material as a function of evolutionary age and initial rotational velocities; the second effect provides significant further evidence that very massive stars mix while still on the main sequence. Thus, further analysis of these features will likely provide valuable diagnostics of important evolutionary parameters.

Opening the Treasure Chest: A Newborn Star Cluster Emerges from Its Dust Pillar in Carina

We present detailed observations of the Treasure Chest, a compact nebula at the head of a dust pillar in the southern Carina Nebula. This object is of interest because it is an example of a dense young cluster containing at least one massive star, the formation of which may have been triggered by feedback from the very massive stars in the Carina Nebula, and possibly η Carinae itself. Our observations include narrowband images of Hα, [S II], [O III], Paβ, [Fe II], and H2, broadband JHK images, and a visual wavelength spectrum of the nebula. We use these data to investigate both the nebular and stellar content of the object. The near-infrared emission-line images reveal a cavity inside the head of the dust pillar, which contains a dense cluster of young stars, whereas the observed spectrum of the nebula is consistent with an H II region ionized by the O9.5 V star CPD -59°2661. The embedded infrared cluster was discovered in Two Micron All Sky Survey data, but our new JHK images have improved spatial resolution and sensitivity, allowing an analysis of the stellar content of the newborn cluster. After subtracting contamination of field stars within the Carina Nebula itself, we compare the cluster's color-magnitude diagram with pre–main-sequence isochrones to derive a likely cluster age of less than about 0.1 Myr. This is in reasonable agreement with the dynamical age of a few times 104 yr for the expanding nebular cavity, indicating extreme youth. Stars in the Treasure Chest cluster are highly reddened, with extinction values as large as AV ~ 50. Two-thirds of cluster members show strong infrared excess colors indicative of circumstellar disks, which may prove to be among the highest fraction yet seen for a young cluster once L-band photometry is considered. All evidence suggests that the Treasure Chest is an extremely young cluster that is just now breaking out of its natal cloud into the surrounding massive star-forming region and is a good target for more detailed study.

Results from the South Pole Infra-Red EXplorer Telescope

AbstractThe SPIREX telescope, located at the Amundsen-Scott South Pole Station, was a prototype system developed to exploit the excellent conditions for IR observing at the South Pole. Observations over two winter seasons achieved remarkably deep, high-resolution, wide-field images in the 3-5 μm wavelength regime. Several star forming complexes were observed, including NGC 6334, Chamaeleon I, η Chamaeleontis, the Carina Nebula, 30 Doradus, RCW 57, RCW 38, as well as the Galactic Center. Images were obtained of lines at 2.42/μm H2, 3.29/μm PAH and 4.05/μm Br α, as well as 3.5/μm L-band and 4.7 μm M-band continuum emission. These data, combined with near-IR, mid-IR, and radio continuum maps, reveal the environments of these star forming sites, as well as any protostars lying within them. The SPIREX project, its observing and reduction methods, and some sample data are summarized here.

G287.84-0.82: an infrared star cluster in the Carina nebula

We have studied the properties of an infrared cluster embedded in the gas and dust of the southern part of the Carina Nebula (NGC 3372), where the probable existence of current star formation has already been predicted. We used mid-infrared (A & C bands) and near-infrared (J H K$_{\rm s}$) images from the MSX and the 2MASS surveys respectively, combined with an optical H$_\alpha$ narrow-band filter image obtained at the CTIO. The infrared star cluster has at least 17 members, and its parameters, radius and stellar density are in very good agreement with high- to intermediate-mass star formation scenarios. The detected IR sources have roughly the same intrinsic infrared excess determined from their position in colour-colour and colour-magnitude diagrams, suggesting that these objects could be related to pre-main sequence stars of high to intermediate mass. Furthermore, we present a low-dispersion spectrum of LS 1883 (O9.5 V) star located near the centre of the IR cluster. The position of this object in the colour-colour and colour-magnitude IR diagrams lies close to the reddening vector of an ZAMS O9 V spectral type star, and it seems to be the first star of this cluster to emerge. All these facts are consistent with the current star-forming scenarios associated with highly embedded star clusters.

Origin of diffuse C II 158 micron and Si II 35 micron emission in the Carina nebula

We present the results of mapping observations with ISO of (O  )6 3µm, 145 µm, (N ) 122 µm, (C ) 158 µm, (Si  )3 5µm, and H2 9.66 µm line emissions for the Carina nebula, an active star-forming region in the Galactic plane. The observations were made for the central 40 � × 20 � area of the nebula, including the optically bright H  region and molecular cloud lying in front of the ionized gas. Around the center of the observed area is the interface between the H  region and the molecular cloud which creates a typical photodissociation region (PDR). The (C ) 158 µm emission shows a good correlation with the (O  )6 3µm emission and peaks around the H -molecular region interface. The correlated component has the ratio of (C ) 158 µ mt o (O )6 3µm of about 2.8. We estimate from the correlation that about 80% of (C ) emission comes from the PDR in the Carina nebula. The photoelectric heating efficiency estimated from the ratio of the ((C ) 158 µm + (O  )6 3µm) intensity to the total far-infrared intensity ranges from 0.06 to 1.2%. (O ) 145 µm is detected marginally at 10 positions. The average ratio of (O ) 145 µ mt o (O )6 3µm of these positions is about 0.09 ± 0.01 and is larger than model predictions. The observed (C ) 158 µ mt o (O )6 3µm ratio indicates a relatively low temperature (<500 K) of the gas, while the large (O ) 145 µ mt o 63µm ratio suggests a high temperature (∼1000 K). This discrepancy cannot be accounted for consistently by the latest PDR model with the efficient photoelectric heating via polycyclic aromatic hydrocarbons (PAHs) even if absorption of (O  )6 3µm by foreground cold gas is taken into account. We suggest that absorption of (C ) 158 µm together with (O  )6 3µm by overlapping PDRs, in which the heating via PAHs is suppressed due to the charge-up effect, may resolve the discrepancy. Quite strong (Si  )3 5µm emission has been detected over the observed area. It shows a good correlation with (N ) 122 µm, but the correlation with (O  )6 3µm is very weak, indicating that (Si  )3 5µm comes mainly from the diffuse ionized gas rather than the PDR. The ratio of (Si  )3 5µ mt o (N) 122 µm is about 8 and Si of about 50% of the solar abundance relative to N should be present in the gas phase. The present results suggest that efficient dust destruction takes place and a large fraction of Si returns to the gas in the Carina star-forming region.

Resolving OB Systems in the Carina Nebula with theHubble Space TelescopeFine Guidance Sensor

We observed 23 OB stars in the Carina Nebula (NGC 3372) with the Hubble Space Telescope's Fine Guidance Sensor 1r (FGS1r) in its high angular resolution mode. Five of these OB stars are newly resolved binaries with projected separations ranging from 0015 to 0352 (37 to 880 AU at a distance of 2.5 kpc), and V-band magnitude differences ranging from 0.9 to 2.8. The most important astrophysical result is the unexpected resolution of the prototype O2 If* star HD 93129A as a 55 milliarcsecond (mas) double with a ΔmV of 0.9. This object has served as a spectroscopic benchmark for the analysis of the most massive hot stars and their winds on the prior assumption that it is a single star. This discovery supports the interpretation of recent radio and X-ray observations as evidence of colliding-wind phenomena in HD 93129A. Another interesting result is the determination of an upper limit of about 35 AU for the projected separation of the binary pairs in the hierarchical double spectroscopic binary HD 93206. The high incidence of resolved binaries provides motivation for a more thorough, statistically meaningful study of multiplicity among the most massive stars in the young ionizing clusters of the nebula to obtain a complete sample of the long-period systems that have evaded spectroscopic detection. However, considering that the nine spectroscopic binaries with accurate orbits in the Carina Nebula have orbital dimensions 1 AU, which at a distance of 2.5 kpc subtends an angle of only 0.4 mas, well below the 10 mas angular resolution of FGS1r, there remains a significant range of orbital periods and separations over which it is very difficult to detect multiplicity in the nebula with currently available instruments.

Carina's defiant Finger:HSTobservations of a photoevaporating globule in NGC 3372★

We present Hubble Space Telescope Wide Field Planetary Camera 2 images of a prominent externally-ionized molecular globule in the Carina Nebula (NGC 3372), supplemented with ground-based infrared images and visual-wavelength spectra. This molecular globule has a shape resembling a human hand, with an extended finger that points toward its likely source of ionizing radiation. Following an analysis of the spatially-resolved ionization structure and spectrum of the photoevaporative flow from the Finger, we conclude that the dominant ionizing source is either the WNL star WR25 (HD 93162), the adjacent O4 If-type star Tr16-244, or perhaps both. We estimate a mass-loss rate of ∼2×10 −5 M⊙ yr −1 from the main evaporating surface of the globule, suggesting a remaining lifetime of 10 5.3 to 10 6 years. We find a total mass for the entire globule of more than 6 M⊙, in agreement with previous estimates. The hydrogen column density through the globule derived from extinction measurements is a few times 10 22 cm −2 , so the photodissociation region behind the ionization front should be limited to a thin layer compared to the size of the globule, in agreement with the morphology seen in H2 images. Although a few reddened stars are seen within the boundary of the globule in near-infrared continuum images, these may be background stars. We do not detect a reddened star at the apex of the finger, for example, down to a limiting magnitude of mK ≃17. However, considering the physical properties of the globule and the advancing ionization front, it appears that future star formation is likely in the Finger globule, induced by radiation-driven implosion.

The systemic velocity of Eta Carinae★

High-resolution spectra of molecular hydrogen in the Homunculus nebula allow for the first direct measurement of the systemic velocity of Eta Carinae. Near-infrared long-slit data for H2 1-0 S(1) lambda 21218 obtained with the Phoenix spectrometer on the Gemini South telescope give Vsys=-8.1pm1 km/s (heliocentric), or VLSR=-19.7pm1 km/s, from the average of the near and far sides of the Homunculus. This measurement considerably improves the precision for the value of -7pm10 km/s inferred from neighboring O-type stars in the Carina nebula. New near-infrared spectra also provide a high-resolution line profile of [Fe II] lambda 16435 emission from gas condensations known as the Weigelt objects without contamination from the central star, revealing a line shape with complex kinematic structure. Previously, uncertainty in the Weigelt knots' kinematics was dominated by the adopted systemic velocity of Eta Car.

HH 666: The Axis of Evil in the Carina Nebula

We report the discovery of the iniquitous parsec-scale outflow HH 666—the first protostellar jet in the Carina Nebula—as well as the infrared identification of its embedded driving source. The HH 666 jet emanates from a bright-rimmed molecular globule (G287.57-0.91) at the head of a dust pillar in the southern part of Carina. Optical and near-infrared images reveal structures that resemble bow shocks and internal working surfaces in other Herbig-Haro (HH) jets, and which are especially bright in [Fe II] λ16435. Except for extended bow shock wings, all features lie within a few degrees of a single axis oriented roughly southeast to northwest, with a remarkable highly collimated flow breaking out of the natal globule. Long-slit echelle spectra reveal only redshifted velocities toward the southeast of the globule and blueshifted velocities toward the northwest. The observed features conspire to form a single, coherent bipolar jet with a total projected length of over 45, or more than 3 pc. Doppler shifts as high as ±250 km s-1 are seen, indicating that the jet axis has a significant tilt from the plane of the sky, and the total length of the jet may be closer to 4 or 5 pc. HH 666 is therefore among the longest HH jets known. Condemned to toil in the inferno of the Carina Nebula, scorched by UV radiation from the hot stars that power the H II region, much of the jet is influenced by radiative excitation. Infrared images reveal a reddened star embedded in the molecular globule lying along the jet axis. We identify this evildoer (HH 666 IRS) as the likely driving source of the jet. The infrared spectral energy distribution of HH 666 IRS is consistent with that of a Class I protostellar object, with a luminosity of a few hundred to 103 L⊙, and a probable main-sequence mass of a few to 8 M⊙. This Class I object associated with a prominent bipolar jet constitutes the first direct evidence of ongoing active star formation by accretion in the Carina Nebula.

The giant pillars of the Carina Nebula

Results are presented from a multi-wavelength study of the giant pillars within the Carina Nebula. Using near-IR data from 2MASS, mid-IR data from MSX, 843 MHz radio continuum maps from the MOST and molecular line and continuum observations from the SEST, we investigate the nature of the pillars and search for evidence of ongoing star formation within them. Photodissociation regions (PDRs) exist across the whole nebula and trace the giant pillars, as well as many ridges, filaments and condensations (A v > 7 mag). Morphological similarities between emission features at 21 μm and 843MHz adjacent to the PDRs, suggests that the molecular material has been carved by the intense stellar winds and UV radiation from the nearby massive stars. In addition, star forming cores are found at the tips of several of the pillars. Using a stellar density distribution, several candidate embedded clusters are also found. One is clearly seen in the 2MASS images and is located within a dense core (G287.84-0.82). A search for massive young stellar objects and compact H II regions using mid-IR colour criteria, reveal twelve candidates across the complex. Grey-body fits to SEDs for four of these objects are suggestive of OB-stars. We find that massive star formation in the Carina Nebula is occurring across the whole complex and confirm it has been continuous over the past 3 Myrs.