Carina Nebula Research Articles

Gaussian Denoising for the First Image from The James Webb Space Telescope “Carina Nebula” using Non-Linear Filters

Noise, including Gaussian noise, distorts images during transition or acquisition process, reducing required information. Removing or reducing this noise is crucial in image processing. The James Webb Space Telescope (JWST) is a vital tool for enhancing our understanding of the universe, providing valuable scientific data and inspiring global interest. In this paper we introduce several nonlinear (Non-Local Mean, Bilateral, and classical) filters to remove the Gaussian noise from the Carina Nebula Image, the first image taken by (JWST) on 12 July 2022. These nonlinear filters were therefore selected to highlight the significance of selecting the right technique that can handle, process, and preserve as many details as possible. They also serve to elucidate the degree of advancement achieved in the field of denoising and the distinction between the classical filters and the more sophisticated filters that have evolved to handle finer details. Classic filters deal with the pixels themselves and their neighbors and then perform the desired statistical process. While advanced filters consider the similarities and distances between the central pixel and its neighbors, they preserve the edges of the image as advanced features. Based on quality measurements (PSNR) and (SSIM), the filter results were compared. The results show that the Bilateral filter gives high performance in restoring images under different Gaussian noise densities compared with the other denoising filters where it gives values of (30.65) and (0.93) for (PSNR) and (SSIM) respectively Which is higher than the results of the filters. Paper type :Research paper.

EROSITA studies of the Carina nebula

Context. During the first four all-sky surveys eRASS:4, which was carried out from December 2019 to 2021, the extended Roentgen Survey with an Imaging Telescope Array (eROSITA) on board the Spektrum-Roentgen-Gamma (Spektr-RG, SRG) observed the Galactic H II region, the Carina nebula. Aims. We analysed the eRASS:4 data to study the distribution and spectral properties of the hot interstellar plasma and the bright stellar sources in the Carina nebula. Methods. The spectral extraction regions of the diffuse emission were defined based on the X-ray spectral morphology and multi-wavelength data. The spectra were fit with a combination of thermal and non-thermal emission models. The X-ray bright point sources in the Carina nebula are the colliding wind binary η Car, several O stars, and Wolf–Rayet (WR) stars. We extracted the spectra of the brightest stellar sources, which can be well fit with a multi-component thermal plasma model. Results. The spectra of the diffuse emission in the brighter parts of the Carina nebula are well reproduced by two thermal models, a lower-temperature component (~0.2 keV) and a higher-temperature component (0.6–0.8 keV). An additional non-thermal component dominates the emission above ~1 keV in the Central region around η Car and the other massive stars. Significant orbital variation in the X-ray flux was measured for η Car, WR 22, and WR 25. η Car requires an additional time-variable thermal component in the spectral model, which is associated with the wind-wind collision zone. Conclusions. Properties such as temperature, pressure, and luminosity of the X-ray emitting plasma in the Carina nebula derived from the eROSITA data are consistent with theoretical calculations of emission from superbubbles. This confirms that the X-ray emission is caused by the hot plasma inside the Carina nebula that has been shocked-heated by the stellar winds of the massive stars, in particular, of η Car.

Into the Mystic: ALMA ACA observations of the Mystic Mountains in Carina

ABSTRACT We present new observations of the Mystic Mountains cloud complex in the Carina Nebula using the ALMA Atacama Compact Array (ACA) to quantify the impact of strong UV radiation on the structure and kinematics of the gas. Our Band 6 observations target CO, 13CO, and C18O; we also detect DCN J=3–2 and 13CS J=5–4. A dendrogram analysis reveals that the Mystic Mountains are a coherent structure, with continuous emission over −10.5 km s−1 < v < −2 km s−1. We perform multiple analyses to isolate non-thermal motions in the Mystic Mountains including computing the turbulent driving parameter, b, which indicates whether compressive or solenoidal modes dominate. Each analysis yields values similar to other pillars in Carina that have been observed in a similar way but are subject to an order of magnitude less intense ionizing radiation. We find no clear correlation between the velocity or turbulent structure of the gas and the incident radiation, in contrast to other studies targeting different regions of Carina. This may reflect differences in the initial densities of regions that go on to collapse into pillars and those that still look like clouds or walls in the present day. Pre-existing over-densities that enable pillar formation may also explain why star formation in the pillars appears more evolved (from the presence of jets) than in other heavily irradiated but non-pillar-like regions. High resolution observations of regions subject to an array of incident radiation are required to test this hypothesis.

COMPARING THE STAR FORMATION RATES OF 2 STAR FORMING REGIONS

This paper introduces nebulae and the process of star formation. It then focuses on analysing the compositions and star formation rates of NGC 3603 (an open cluster in NGC 3372, also known as the Carina Nebula) and L 1641 (a molecular cloud in Orion A, part of the Orion Molecular Cloud Complex). It then compares both regions and concludes that NGC 3603 has a higher rate of star formation than L 1641.

Gaia-ESO survey: Massive stars in the Carina Nebula

Context. The Carina Nebula is one of the major massive star-forming regions in the Galaxy. Its relatively nearby distance (2.35 kpc) makes it an ideal laboratory for the study of massive star formation, structure, and evolution, both for individual stars and stellar systems. Thanks to the high-quality spectra provided by the Gaia-ESO survey and the LiLiMaRlin library, as well as Gaia EDR3 astrometry, a detailed and homogeneous spectroscopic characterization of its massive stellar content can be carried out. Aims. Our main objective is to spectroscopically characterize all massive members of the Carina Nebula in the Gaia-ESO survey footprint to provide an updated census of massive stars in the region and an updated estimate of the binary fraction of O stars. Methods. We performed accurate spectral classification using an interactive code that compares spectra with spectral libraries of OB standard stars, as well as line-based classic methods. We calculated membership using our own algorithm based on Gaia EDR3 astrometry. To check the correlation between the spectroscopic n-qualifier and the rotational velocity, we used a semi-automated tool for the line-broadening characterization of OB stars based on a combined Fourier transform and goodness-of-fit methodology. Results. The Gaia-ESO survey sample of massive OB stars in the Carina Nebula consists of 234 stars. The addition of brighter sources from the Galactic O-Star Spectroscopic Survey and additional sources from the literature allows us to create the most complete census of massive OB stars so far in the region. It contains a total of 316 stars, with 18 of them in the background and 4 in the foreground. Of the 294 stellar systems in Car OB1, 74 are of O type, 214 are of nonsupergiant B type, and 6 are of WR or nonO supergiant (II to Ia) spectral class. We identify 20 spectroscopic binary systems with an O-star primary, of which 6 are reported for the first time, and another 18 with a B-star primary, of which 13 are new detections. The average observed double-lined binary fraction of O-type stars in the surveyed region is 0.35, which represents a lower limit. We find a good correlation between the spectroscopic n-qualifier and the projected rotational velocity of the stars. The fraction of candidate runaways among the stars with and without the n-qualifier is 4.4% and 2.4%, respectively, although nonresolved double-lined binaries could be contaminating the sample of fast rotators.

Length-scales and dynamics of Carina’s Western wall

ABSTRACT We present a variety of analyses of the turbulent dynamics of the boundary of a photodissociation region (PDR) in the Carina Nebula using high resolution ALMA observations. Using principal component analysis, we suggest that the turbulence in this molecular cloud is driven at large scales. Analysis of the centroid velocity structure functions indicate that the turbulence is dominated by shocks rather than local (in k-space) transport of energy. We further find that length-scales in the range 0.02–0.03 pc are important in the dynamics of this cloud and this finding is supported by analysis of the dominant emission structure length-scale. These length-scales are well resolved by the observational data and we conclude that the apparent importance of this range of scales is physical in origin. Given that it is also well within the range strongly influenced by ambipolar diffusion, we conclude that it is not primarily a product of turbulence alone, but is more likely to be a result of the interplay between gravity and turbulence. Finally, through comparison of these results with previous observations of H2 emission from the Western Wall, we demonstrate that observations of a PDR can be used to probe the internal structure of the undisturbed portion of a molecular cloud.

The content and consequence of the first data release from the James Webb Space Telescope

<p indent="0mm">The James Webb Space Telescope (JWST) is the biggest and the most expensive space telescope project led by NASA. The observation band of <sc>0.7–29 μm</sc> with various image cameras, spectrographs, and coronagraphic instruments enables us to explore the universe from planets to high-redshift galaxies. On 11 and 12 July 2022, NASA released the early release observation (ERO) data of the JWST, including not only beautiful pictures but also scientific data. The impressive data reveal extraordinary details of the HII region, compact galaxy group, planetary nebular, exoplanet atmosphere, and galaxy clusters, demonstrating the power of the JWST. In this paper, we briefly introduce the first release of the ERO data, and discuss the impact of the JWST on the astronomy. The five datasets released by the JWST ERO are: (1) Carina Nebula, which is a star formation region in the Galaxy including several O type stars, diffuse gas and dust. (2) Stephan’s Quintet, one of the most famous nearby galaxy groups that consist of four interacting galaxies and one foreground galaxy. The ERO data includes the NIRCam and MIRI images and the integral field unit (IFU) spectra data that enable us to study various topics such as the galaxy dynamics, shockwave, metallicity, black hole accretion, and so on. (3) Southern Ring Nebula, which is a nebular ejected by the center star during the late evolution stage. The new data reveal the center old star blocked by the dust. (4) WASP-96 b, which is an exoplanet discovered in 2004. The released data of WASP-96 b are the atmosphere spectrum, in which we can see clear water feature. (5) SMACS 0723, which is a galaxy cluster at redshift 0.4. The released data include the NIRCam, MIRI image, as well as the spectra from NIRSS and NIRSpec. The release of the ERO includes the raw and science-ready data reduced by the default JWST pipeline. Besides the data release, the JWST team also provides the document website to introduce the telescope instruments, the data reduction pipeline, and post-pipeline reduction suggestions, and organizes web seminars since 2021 to help users understand the telescope and data. The open-access of the ERO data has been stimulating astronomers all over the world to explore the universe through this new window. In the first month after the JWST data release, there are about 2–4 new papers submitted from competing groups to preprint website astro-ph. The active studies based on the JWST data would also help the improvement of the pipeline and the configuration of the instrument for the next proposal cycle. In general, with unrivaled data quality, the JWST is opening a new window for astronomers, and helping astronomers explore the new edge of the universe.

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.

Changes in the Na D1 Absorption Components of η Carinae Provide Clues on the Location of the Dissipating Central Occulter

The Na D absorption doublet in the spectrum of η Carinae is complex, with multiple absorption features associated with the Great Eruption (1840s), the Lesser Eruption (1890s), and the interstellar clouds. The velocity profile is further complicated by the P Cygni profile originating in the system’s stellar winds and blending with the He i λ5876 profile. The Na D profile contains a multitude of absorption components, including those at velocities of −145 km s−1, −168 km s−1, and +87 km s−1, which we concentrate on in this analysis. Ground-based spectra recorded from 2008 to 2021 show significant variability of the −145 km s−1 absorption throughout long-term observations. In the high-ionization phases of η Carinae prior to the 2020 periastron passage, this feature disappeared completely but briefly reappeared across the 2020 periastron, along with a second absorption at −168 km s−1. Over the past few decades, η Carinae has been gradually brightening, which is shown to be caused by a dissipating occulter. The decreasing absorption of the −145 km s−1 component, coupled with similar trends seen in absorptions of ultraviolet resonant lines, indicate that this central occulter was possibly a large clump associated with the Little Homunculus or another clump between the Little Homunculus and the star. We also report on a foreground absorption component at +87 km s−1. Comparison of Na D absorption in the spectra of nearby systems demonstrates that this redshifted component likely originates in an extended foreground structure consistent with a previous ultraviolet spectral survey in the Carina Nebula.

First James Webb Space Telescope´s images

From left to right and from top to bottom: 1. The Stephan's Quintet (interacting galaxies' group), 40 million and 290 million light-years away; 2. The Cartwheel Galaxy, a merger of galaxies of 144,300 light-years across, 500 million light-years away; 3. The spectrum of the exoplanet WASP-96b (1,150 light-years away), showing evaporated water; 4. James Webb telescope in its clean room; 5. The South Ring Nebula, 2,500 light-years away (12 light-years across); 6. Galactic cluster in the early universe SMACS 07323, 4,600,000,000 light-years away; 7. The star formation region NGC 3324 (Gabriela Mistral) in the Carina Nebula (NGC3372), 7,600 light-years away.

X-ray properties of early-type stars in the Tarantula Nebula from T-ReX

ABSTRACT We reassess the historical LX/LBol relation for early-type stars from a comparison between T-ReX, the Chandra ACIS X-ray survey of the Tarantula Nebula in the Large Magellanic Cloud (LMC), and contemporary spectroscopic analysis of massive stars obtained primarily from VLT/FLAMES, VLT/MUSE, and HST/STIS surveys. For 107 sources in common (some host to multiple stars), the majority of which are bolometrically luminous (40 per cent exceed 106L⊙), we find an average log LX/LBol = −6.90 ± 0.65. Excluding extreme systems Mk 34 (WN5h+WN5h), R140a (WC4+WN6+), and VFTS 399 (O9 IIIn+?), plus four WR sources with anomalously hard X-ray components (R130, R134, R135, Mk 53) and 10 multiple sources within the spatially crowded core of R136a, log LX/LBol = −7.00 ± 0.49, in good agreement with Galactic OB stars. No difference is found between single and binary systems, nor between O, Of/WN, and WR stars, although there does appear to be a trend towards harder X-ray emission from O dwarfs, through O (super)giants, Of/WN stars, and WR stars. The majority of known OB stars in the Tarantula are not detected in the T-ReX point source catalogue, so we have derived upper limits for all undetected OB stars for which log LBol/L⊙ ≥ 5.0. A survival analysis using detected and upper limit log LX/LBol values indicates no significant difference between luminous O stars in the LMC and the Carina Nebula. This analysis suggests that metallicity does not strongly influence LX/LBol. Plasma temperatures for single, luminous O stars in the Tarantula ($\overline{kT_{m}}=1.0$ keV) are higher than counterparts in Carina ($\overline{kT_{m}}=0.5$ keV).

Carina, Carina

Carina, Carina

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.

Characterizing the X-Ray Emission of Intermediate-mass Pre-main-sequence Stars

Abstract We use X-ray and infrared observations to study the properties of three classes of young stars in the Carina Nebula: intermediate-mass (2–5 M ⊙) pre-main-sequence stars (IMPS; i.e., intermediate-mass T Tauri stars), late-B and A stars on the zero-age main sequence (AB), and lower-mass T Tauri stars (TTS). We divide our sources among these three subclassifications and further identify disk-bearing young stellar objects versus diskless sources with no detectable infrared (IR) excess emission using IR (1–8 μm) spectral energy distribution modeling. We then perform X-ray spectral fitting to determine the hydrogen-absorbing column density (N H ), absorption-corrected X-ray luminosity (L X ), and coronal plasma temperature (kT) for each source. We find that the X-ray spectra of both IMPS and TTS are characterized by similar kT and N H , and on average L X /L bol ∼ 4 × 10−4. IMPS are systematically more luminous in X-rays (by ∼0.3 dex) than all other subclassifications, with median L X = 2.5 × 1031 erg s−1, while AB stars of similar masses have X-ray emission consistent with TTS companions. These lines of evidence converge on a magnetocoronal flaring source for IMPS X-ray emission, a scaled-up version of the TTS emission mechanism. IMPS therefore provide powerful probes of isochronal ages for the first ∼10 Myr in the evolution of a massive stellar population, because their intrinsic, coronal X-ray emission decays rapidly after they commence evolving along radiative tracks. We suggest that the most luminous (in both X-rays and IR) IMPS could be used to place empirical constraints on the location of the intermediate-mass stellar birth line.

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.

Gaia EDR3 Parallax Distances to the Great Carina Nebula and Its Star Clusters (Trumpler 14, 15, 16)

Abstract Using offset-corrected Gaia EDR3 parallax measurements and spectrophotometric methods, we have determined distances for 69 massive stars in the Carina OB1 association and associated clusters: Trumpler 16 (21 stars), Trumpler 14 (20 stars), Trumpler 15 (three stars), Bochum 11 (five stars), and South Pillars region (20 stars). Past distance estimates to the Carina Nebula range from 2.2 to 3.6 kpc, with uncertainties arising from photometry and anomalous dust extinction. The EDR3 parallax solutions show considerable improvement over DR2, with typical errors σ ϖ /ϖ ≈ 3%–5%. The O-type stars in the Great Carina Nebula lie at essentially the same distance (2.35 ± 0.08 kpc), quoting mean and rms variance. The clusters have distances of 2.32 ± 0.12 kpc (Tr 16), 2.37 ± 0.15 kpc (Tr 14), 2.36 ± 0.09 kpc (Tr 15), and 2.33 ± 0.12 kpc (Bochum 11) in good agreement with the η Car distance of around 2.3 kpc. O-star proper motions suggest internal (3D) velocity dispersions ∼4 km s−1 for Tr 14 and Tr 16. Reliable distances allow estimates of cluster sizes, stellar dynamics, luminosities, and fluxes of photoionizing radiation incident on photodissociation regions in the region. We estimate that Tr 14 and Tr 16 have half-mass radii r h = 1.5–1.8 pc, stellar crossing times t cr = r h/v m ≈ 0.7–0.8 Myr, and two-body relaxation times t rh ≈ 40–80 Myr. The underlying velocity dispersion for Tr 14, if a bound cluster, would be km s−1 for stars. With the higher dispersions of the O stars, inward drift would occur slowly, on timescales of 3–6 Myr.

Detection of new O-type stars in the obscured stellar cluster Tr 16-SE in the Carina Nebula with KMOS

Context.The Carina Nebula harbors a large population of high-mass stars, including at least 75 O-type and Wolf-Rayet (WR) stars, but the current census is not complete since further high-mass stars may be hidden in or behind the dense dark clouds that pervade the association.Aims.With the aim of identifying optically obscured O- and early B-type stars in the Carina Nebula, we performed the first infrared spectroscopic study of stars in the optically obscured stellar cluster Tr 16-SE, located behind a dark dust lane south ofηCar.Methods.We used the integral-field spectrograph KMOS at the ESO VLT to obtainH- andK-band spectra with a resolution ofR ≈ 4000 (Δλ≈ 5 Å) for 45 out of the 47 possible OB candidate stars in Tr 16-SE, and we derived spectral types for these stars.Results.We find 15 stars in Tr 16-SE with spectral types between O5 and B2 (i.e., high-mass stars withM ≥ 8 M⊙), only two of which were known before. An additional nine stars are classified as (Ae)Be stars (i.e., intermediate-mass pre-main-sequence stars), and most of the remaining targets show clear signatures of being late-type stars and are thus most likely foreground stars or background giants unrelated to the Carina Nebula. Our estimates of the stellar luminosities suggest that nine of the 15 O- and early B-type stars are members of Tr 16-SE, whereas the other six seem to be background objects.Conclusions.Our study increases the number of spectroscopically identified high-mass stars (M ≥ 8 M⊙) in Tr 16-SE from two to nine and shows that Tr 16-SE is one of the larger clusters in the Carina Nebula. Our identification of three new stars with spectral types between O5 and O7 and four new stars with spectral types O9 to B1 significantly increases the number of spectroscopically identified O-type stars in the Carina Nebula.

The Carina Nebula and Gum 31 Molecular Complex. III. The Distribution of the 1–3 GHz Radio Continuum across the Whole Nebula

Abstract We report the most detailed 1–3 GHz radio continuum emission map of the nearest region of massive-star formation, the Carina Nebula. As part of a large program with the Australia Telescope Compact Array, we have covered ∼12 deg2, achieving an angular resolution of ∼16″, representing the largest and most complete map of the radio continuum to date. Our continuum map shows a spectacular and complex distribution of emission across the nebula, with multiple structures such as filaments, shells, and fronts across a wide range of size scales. The ionization fronts have advanced far into the southern and northern region of the Galactic plane, as fronts are clearly detected at distances of ∼80 pc from the stellar clusters in the center. We estimated an ionization photon luminosity Q H = (7. 8 ± 0.8) × 1050 s−1, which corresponds to ∼85% of the total value obtained from stellar population studies. Thus, approximately 15% of the ionizing flux has escaped from the nebula into the diffuse Galactic interstellar medium. Comparison between radio continuum and the hydrogen atomic and molecular gas maps offers a clear view of the bipolar outflow driven by the energy released by the massive stellar clusters that also affects the fraction of molecular gas across the nebula. Comparison between 8 μm and 70 μm emission maps and the radio continuum reveals how the hot gas permeates through the molecular cloud; shapes the material into features such as pillars, small shells, and arc-like structures; and ultimately escapes.

On the compressive nature of turbulence driven by ionizing feedback in the pillars of the Carina Nebula

ABSTRACT The ionizing radiation of massive stars sculpts the surrounding neutral gas into pillar-like structures. Direct signatures of star formation through outflows and jets are observed in these structures, typically at their tips. Recent numerical simulations have suggested that this star formation could potentially be triggered by photoionizing radiation, driving compressive modes of turbulence in the pillars. In this study, we use recent high-resolution ALMA observations of 12CO, 13CO, and C18O, J = 2 − 1 emission to test this hypothesis for pillars in the Carina Nebula. We analyse column density and intensity-weighted velocity maps, and subtract any large-scale bulk motions in the plane of the sky to isolate the turbulent motions. We then reconstruct the dominant turbulence driving mode in the pillars, by computing the turbulence driving parameter b, characterized by the relation $\sigma _{\rho /\rho _0} = b \mathcal {M}$ between the standard deviation of the density contrast $\sigma _{\rho /\rho _0}$ (with gas density ρ and its average ρ0) and the turbulent Mach number $\mathcal {M}$. We find values of b ∼ 0.7–1.0 for most of the pillars, suggesting that predominantly compressive modes of turbulence are driven in the pillars by the ionizing radiation from nearby massive stars. We find that this range of b values can produce star formation rates in the pillars that are a factor ∼3 greater than with b ∼ 0.5, a typical average value of b for spiral-arm molecular clouds. Our results provide further evidence for the potential triggering of star formation in pillars through compressive turbulent motions.