scholarly journals The CO-dark molecular gas mass in 30 Doradus

2020 ◽  
Vol 494 (4) ◽  
pp. 5279-5292 ◽  
Author(s):  
Mélanie Chevance ◽  
Suzanne C Madden ◽  
Christian Fischer ◽  
William D Vacca ◽  
Vianney Lebouteiller ◽  
...  
Keyword(s):  
Massive Star ◽  
Large Fraction ◽  
Accurate Determination ◽  
Large Magellanic Cloud ◽  
Scaling Relations ◽  
Molecular Gas ◽  
Large Reservoir ◽  
Star Forming ◽  
The Impact ◽  
30 Doradus

ABSTRACT Determining the efficiency with which gas is converted into stars in galaxies requires an accurate determination of the total reservoir of molecular gas mass. However, despite being the most abundant molecule in the Universe, H2 is challenging to detect through direct observations and indirect methods have to be used to estimate the total molecular gas reservoir. These are often based on scaling relations from tracers such as CO or dust, and are generally calibrated in the Milky Way. Yet, evidence that these scaling relations are environmentally dependent is growing. In particular, the commonly used CO-to-H2 conversion factor (XCO) is expected to be higher in metal-poor and/or strongly UV-irradiated environments. We use new SOFIA/FIFI-LS observations of far-infrared fine-structure lines from the ionized and neutral gas and the Meudon photodissociation region model to constrain the physical properties and the structure of the gas in the massive star-forming region of 30 Doradus in the Large Magellanic Cloud, and determine the spatially resolved distribution of the total reservoir of molecular gas in the proximity of the young massive cluster R136. We compare this value with the molecular gas mass inferred from ground-based CO observations and dust-based estimates to quantify the impact of this extreme environment on commonly used tracers of the molecular gas. We find that the strong radiation field combined with the half-solar metallicity of the surrounding gas is responsible for a large reservoir of ‘CO-dark’ molecular gas, leaving a large fraction of the total H2 gas (≳75 per cent) undetected when adopting a standard XCO factor in this massive star-forming region.

scholarly journals Radiative and mechanical feedback into the molecular gas in the Large Magellanic Cloud

2019 ◽  
Vol 628 ◽  
pp. A113 ◽  
Author(s):  
M.-Y. Lee ◽  
S. C. Madden ◽  
F. Le Petit ◽  
A. Gusdorf ◽  
P. Lesaffre ◽  
...  
Keyword(s):  
Far Infrared ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Continuum Emission ◽  
Molecular Gas ◽  
Stellar Content ◽  
Low Velocity ◽  
Line Energy ◽  
Star Forming ◽  
30 Doradus

With an aim of probing the physical conditions and excitation mechanisms of warm molecular gas in individual star-forming regions, we performed Herschel SPIRE Fourier Transform Spectrometer (FTS) observations of 30 Doradus in the Large Magellanic Cloud. In our FTS observations, important far-infrared (FIR) cooling lines in the interstellar medium, including CO J = 4–3 to J = 13–12, [C I] 370 μm, and [N II] 205 μm, were clearly detected. In combination with ground-based CO J = 1–0 and J = 3–2 data, we then constructed CO spectral line energy distributions (SLEDs) on ~10 pc scales over a ~60 pc × 60 pc area and found that the shape of the observed CO SLEDs considerably changes across 30 Doradus. For example, the peak transition Jp varies from J = 6–5 to J = 10–9, while the slope characterized by the high-to-intermediate J ratio α ranges from ~0.4 to ~1.8. To examine the source(s) of these variations in CO transitions, we analyzed the CO observations, along with [C II] 158 μm, [C I] 370 μm, [O I] 145 μm, H2 0–0 S(3), and FIR luminosity data, using state-of-the-art models of photodissociation regions and shocks. Our detailed modeling showed that the observed CO emission likely originates from highly compressed (thermal pressure P∕kB ~ 107–109 K cm−3) clumps on ~0.7–2 pc scales, which could be produced by either ultraviolet (UV) photons (UV radiation field GUV ~ 103–105 Mathis fields) or low-velocity C-type shocks (pre-shock medium density npre ~ 104–106 cm−3 and shock velocity vs ~ 5–10 km s−1). Considering the stellar content in 30 Doradus, however, we tentatively excluded the stellar origin of CO excitation and concluded that low-velocity shocks driven by kiloparsec-scale processes (e.g., interaction between the Milky Way and the Magellanic Clouds) are likely the dominant source of heating for CO. The shocked CO-bright medium was then found to be warm (temperature T ~ 100–500 K) and surrounded by a UV-regulated low-pressure component (P∕kB ~ a few (104 –105) K cm−3) that is bright in [C II] 158 μm, [C I] 370 μm, [O I] 145 μm, and FIR dust continuum emission.

scholarly journals High-contrast and resolution near-infrared photometry of the core of R136

2021 ◽  
Vol 503 (1) ◽  
pp. 292-311
Author(s):  
Zeinab Khorrami ◽  
Maud Langlois ◽  
Paul C Clark ◽  
Farrokh Vakili ◽  
Anne S M Buckner ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Outer Region ◽  
Mass Range ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Star Forming ◽  
The Core ◽  
Very Large Telescope ◽  
30 Doradus

ABSTRACT We present the sharpest and deepest near-infrared photometric analysis of the core of R136, a newly formed massive star cluster at the centre of the 30 Doradus star-forming region in the Large Magellanic Cloud. We used the extreme adaptive optics of the SPHERE focal instrument implemented on the ESO Very Large Telescope and operated in its IRDIS imaging mode for the second time with longer exposure time in the H and K filters. Our aim was to (i) increase the number of resolved sources in the core of R136, and (ii) to compare with the first epoch to classify the properties of the detected common sources between the two epochs. Within the field of view (FOV) of 10.8″ × 12.1″ ($2.7\,\text {pc}\times 3.0\, \text {pc}$), we detected 1499 sources in both H and K filters, for which 76 per cent of these sources have visual companions closer than 0.2″. The larger number of detected sources enabled us to better sample the mass function (MF). The MF slopes are estimated at ages of 1, 1.5, and 2 Myr, at different radii, and for different mass ranges. The MF slopes for the mass range of 10–300 M⊙ are about 0.3 dex steeper than the mass range of 3–300 M⊙, for the whole FOV and different radii. Comparing the JHK colours of 790 sources common in between the two epochs, 67 per cent of detected sources in the outer region (r > 3″) are not consistent with evolutionary models at 1–2 Myr and with extinctions similar to the average cluster value, suggesting an origin from ongoing star formation within 30 Doradus, unrelated to R136.

scholarly journals PHIBSS: MOLECULAR GAS CONTENT AND SCALING RELATIONS INz∼ 1-3 MASSIVE, MAIN-SEQUENCE STAR-FORMING GALAXIES

2013 ◽  
Vol 768 (1) ◽  
pp. 74 ◽  
Author(s):  
L. J. Tacconi ◽  
R. Neri ◽  
R. Genzel ◽  
F. Combes ◽  
A. Bolatto ◽  
...  
Keyword(s):  
Main Sequence ◽  
Gas Content ◽  
Main Sequence Star ◽  
Scaling Relations ◽  
Molecular Gas ◽  
Star Forming

scholarly journals High molecular gas fractions in normal massive star-forming galaxies in the young Universe

Nature ◽  
2010 ◽  
Vol 463 (7282) ◽  
pp. 781-784 ◽  
Author(s):  
L. J. Tacconi ◽  
R. Genzel ◽  
R. Neri ◽  
P. Cox ◽  
M. C. Cooper ◽  
...  
Keyword(s):  
Massive Star ◽  
Molecular Gas ◽  
Star Forming ◽  
Gas Fractions

scholarly journals A New Investigation of the 30 Doradus Region with the Australia Telescope Compact Array

1999 ◽  
Vol 190 ◽  
pp. 251-253
Author(s):  
J. S. Lazendic ◽  
R. F. Haynes ◽  
J. R. Dickel ◽  
P. A. Jones ◽  
G. L. White ◽  
...  
Keyword(s):  
Star Formation ◽  
Supernova Remnants ◽  
Massive Stars ◽  
Large Magellanic Cloud ◽  
Complex Nature ◽  
Active Star ◽  
H Ii Region ◽  
The Impact ◽  
Compact Array ◽  
30 Doradus

30 Doradus is a giant H II region in the Large Magellanic Cloud (Bode 1801). It is the nearest extragalactic giant H II region and the location of active star formation. The complex nature of this extended region provides an excellent opportunity to investigate the impact of massive stars on the structure of the interstellar medium. Specifically the presence of supernova remnants (SNRs) is expected to play an important role.

scholarly journals Massive Star Formation in the Ultraviolet Observed with the Hubble Space Telescope

Galaxies ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 13 ◽  
Author(s):  
Claus Leitherer
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Hubble Space Telescope ◽  
Spectral Synthesis ◽  
Star Clusters ◽  
Large Magellanic Cloud ◽  
H Ii Regions ◽  
Massive Star Formation ◽  
Space Telescope ◽  
Star Forming

Spectroscopic observations of a massive star formation in the ultraviolet and their interpretation are reviewed. After a brief historical retrospective, two well-studied resolved star clusters and the surrounding H II regions are introduced: NGC 2070 in the Large Magellanic Cloud and NGC 604 in M33. These regions serve as a training set for studies of more distant clusters, which can no longer be resolved into individual stars. Observations of recently formed star clusters and extended regions in star-forming galaxies in the nearby universe beyond the Local Group are presented. Their interpretation relies on spectral synthesis models. The successes and failures of such models are discussed, and future directions are highlighted. I present a case study of the extraordinary star cluster and giant H II region in the blue compact galaxy II Zw 40. The review concludes with a preview of two upcoming Hubble Space Telescope programs: ULLYSES, a survey of massive stars in nearby galaxies, and CLASSY, a study of massive star clusters in star-forming galaxies.

First Results from Project SUNBIRD: Supernovæ UNmasked By Infra-Red Detection

2017 ◽  
Vol 14 (S339) ◽  
pp. 322-322
Author(s):  
E. C. Kool ◽  
S. D. Ryder ◽  
E. Kankare ◽  
T. Reynolds ◽  
S. Mattila ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Large Fraction ◽  
Accurate Determination ◽  
Star Forming ◽  
Dust Extinction ◽  
Luminous Infrared Galaxies ◽  
Infra Red ◽  
Nuclear Regions ◽  
Guide Star

AbstractMeasurements of current rates of core-collapse supernovæ (CCSNe) suffer from significant uncertainties, probably due to the large fraction of CCSNe that explode in crowded regions which have bright background emission and significant dust extinction. Conventional optical (seeing-limited) SN surveys generally fail to detect them, but including them is crucial to the accurate determination of CCSN rates. Project SUNBIRD aims to tighten the present constraints on the fraction of CCSNe that are missed by conventional SN surveys. We are monitoring more than 25 dusty luminous infrared galaxies that are actively star-forming, for evidence of dust-obscured CCSNe, in an effort to characterise the population of CCSNes exploding in those nuclear regions of dusty LIRGs. We observe in the near-infrared, which is less affected by dust extinction compared to the optical; we are using Gemini South and Keck, and we make use of state-of-the-art laser guide-star adaptive optics instruments to achieve a spatial resolution <0’.1, which is sufficient to resolve close to the galactic nucleus.During the project’s first year we discovered three CCSNe and one candidate one, with nuclear offsets as small as 200 pc, as cited in the poster. Aggregating the new discoveries with the CCSNe found in previous programmes employing AO, we compared the distribution of nuclear offsets of AO CCSN discoveries with all other documented CCSNe discovered in LIRGs. The poster showed that our method is singularly effective at uncovering CCSNe in the nuclear regions of LIRGs, and that while optical surveys dominate SNe discoveries far from a galaxy’s centre, near infra-red AO observations are needed to probe the regions within 1 kpc of the nucleus.

scholarly journals A massive nebula around the luminous blue variable star RMC 143 revealed by ALMA

2019 ◽  
Vol 626 ◽  
pp. A126 ◽  
Author(s):  
C. Agliozzo ◽  
A. Mehner ◽  
N. M. Phillips ◽  
P. Leto ◽  
J. H. Groh ◽  
...  
Keyword(s):  
Mass Loss Rate ◽  
Large Fraction ◽  
Spectral Energy Distribution ◽  
High Mass ◽  
Spectral Energy ◽  
Star Forming ◽  
High Mass Loss ◽  
Luminous Blue Variable ◽  
30 Doradus

The luminous blue variable (LBV) RMC 143 is located in the outskirts of the 30 Doradus complex, a region rich with interstellar material and hot luminous stars. We report the 3σ sub-millimetre detection of its circumstellar nebula with ALMA. The observed morphology in the sub-millimetre is different than previously observed with HST and ATCA in the optical and centimetre wavelength regimes. The spectral energy distribution (SED) of RMC 143 suggests that two emission mechanisms contribute to the sub-mm emission: optically thin bremsstrahlung and dust. Both the extinction map and the SED are consistent with a dusty massive nebula with a dust mass of 0.055 ± 0.018 M⊙ (assuming κ850 = 1.7 cm2 g−1). To date, RMC 143 has the most dusty LBV nebula observed in the Magellanic Clouds. We have also re-examined the LBV classification of RMC 143 based on VLT/X-shooter spectra obtained in 2015/16 and a review of the publication record. The radiative transfer code CMFGEN is used to derive its fundamental stellar parameters. We find an effective temperature of ∼8500 K, luminosity of log(L/L⊙) = 5.32, and a relatively high mass-loss rate of 1.0 × 10−5 M⊙ yr−1. The luminosity is much lower than previously thought, which implies that the current stellar mass of ∼8 M⊙ is comparable to its nebular mass of ∼5.5 M⊙ (from an assumed gas-to-dust ratio of 100), suggesting that the star has lost a large fraction of its initial mass in past LBV eruptions or binary interactions. While the star may have been hotter in the past, it is currently not hot enough to ionize its circumstellar nebula. We propose that the nebula is ionized externally by the hot stars in the 30 Doradus star-forming region.

scholarly journals Recombination line masers in YSOs

2002 ◽  
Vol 206 ◽  
pp. 226-233 ◽  
Author(s):  
Jesús Martín-Pintado
Keyword(s):  
Massive Star ◽  
Laser Emission ◽  
Massive Stars ◽  
Recombination Line ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Millimeter Wavelengths ◽  
The Impact ◽  
Early Phases

Maser emission from recombination lines has been detected towards the Young Stellar Object (YSO) MWC349 and the massive evolved star η Carinae. In spite of extensive searches of recombination line maser emission at millimeter wavelengths towards massive star forming regions, MWC349 remains unique. MWC349 is also a strong recombination line laser in the Far-IR with the largest amplification observed for transitions at wavelengths around 400 μm. The observational properties of the recombination line maser and laser emission from MWC349 are reviewed. Modeling of the maser and laser emission in MWC349 will be used to illustrate the potential of this kind of masers to understand the early phases of the evolution of massive stars. The impact that future instruments like the Herschel, the SMA and specially ALMA, will have in the investigation of recombination line maser emission from YSOs is briefly discussed.

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