scholarly journals The Tarantula Nebula as a template for extragalactic star forming regions from VLT/MUSE and HST/STIS

2016 ◽  
Vol 12 (S329) ◽  
pp. 292-296
Author(s):  
Paul A. Crowther ◽  
Saida M. Caballero-Nieves ◽  
Norberto Castro ◽  
Christopher J. Evans
Keyword(s):  
Massive Stars ◽  
Central Star ◽  
Population Synthesis ◽  
Uv Spectrum ◽  
Star Forming ◽  
Star Forming Regions ◽  
Integral Field Spectroscopy ◽  
Spatially Extended ◽  
Binary Evolution ◽  
Primary Contribution

AbstractWe present VLT/MUSE observations of NGC 2070, the dominant ionizing nebula of 30 Doradus in the LMC, plus HST/STIS spectroscopy of its central star cluster R136. Integral Field Spectroscopy (MUSE) and pseudo IFS (STIS) together provides a complete census of all massive stars within the central 30×30 parsec2 of the Tarantula. We discuss the integrated far-UV spectrum of R136, of particular interest for UV studies of young extragalactic star clusters. Strong He iiλ1640 emission at very early ages (1–2 Myr) from very massive stars cannot be reproduced by current population synthesis models, even those incorporating binary evolution and very massive stars. A nebular analysis of the integrated MUSE dataset implies an age of ~4.5 Myr for NGC 2070. Wolf-Rayet features provide alternative age diagnostics, with the primary contribution to the integrated Wolf-Rayet bumps arising from R140 rather than the more numerous H-rich WN stars in R136. Caution should be used when interpreting spatially extended observations of extragalactic star-forming regions.

scholarly journals Ultraviolet spectra of extreme nearby star-forming regions: Evidence for an overabundance of very massive stars

2021 ◽  
Vol 503 (4) ◽  
pp. 6112-6135
Author(s):  
Peter Senchyna ◽  
Daniel P Stark ◽  
Stéphane Charlot ◽  
Jacopo Chevallard ◽  
Gustavo Bruzual ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Massive Stars ◽  
Stellar Populations ◽  
Population Synthesis ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
High Incidence ◽  
Stellar Population Synthesis ◽  
Stellar Masses

ABSTRACT As deep spectroscopic campaigns extend to higher redshifts and lower stellar masses, the interpretation of galaxy spectra depends increasingly upon models for very young stellar populations. Here we present new HST/COS ultraviolet spectroscopy of seven nearby (<120 Mpc) star-forming regions hosting very young stellar populations (∼4–20 Myr) with optical Wolf–Rayet stellar wind signatures, ideal laboratories in which to benchmark these stellar models. We detect nebular C iii] in all seven, but at equivalent widths uniformly <10 Å. This suggests that even for very young stellar populations, the highest equivalent width C iii] emission at ≥15 Å is reserved for inefficiently cooled gas at metallicities at or below that of the SMC. The spectra also reveal strong C iv P-Cygni profiles and broad He ii emission formed in the winds of massive stars, including some of the most prominent He ii stellar wind lines ever detected in integrated spectra. We find that the latest stellar population synthesis prescriptions with improved treatment of massive stars nearly reproduce the entire range of stellar He ii wind strengths observed here. However, we find that these models cannot simultaneously match the strongest wind features alongside the optical nebular line constraints. This discrepancy can be naturally explained by an overabundance of very massive stars produced by a high incidence of binary mass transfer and mergers occurring on short ≲10 Myr time-scales, suggesting these processes may be crucial for understanding systems dominated by young stars both nearby and in the early Universe.

scholarly journals The Circumstellar Environment of Embedded Massive Stars

2002 ◽  
Vol 12 ◽  
pp. 143-145 ◽  
Author(s):  
Lee G. Mundy ◽  
Friedrich Wyrowski ◽  
Sarah Watt
Keyword(s):  
Massive Star ◽  
Massive Stars ◽  
Low Mass Stars ◽  
Submillimeter Wavelength ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Circumstellar Environments ◽  
Near Future

Millimeter and submillimeter wavelength images of massive star-forming regions are uncovering the natal material distribution and revealing the complexities of their circumstellar environments on size scales from parsecs to 100’s of AU. Progress in these areas has been slower than for low-mass stars because massive stars are more distant, and because they are gregarious siblings with different evolutionary stages that can co-exist even within a core. Nevertheless, observational goals for the near future include the characterization of an early evolutionary sequence for massive stars, determination if the accretion process and formation sequence for massive stars is similar to that of low-mass stars, and understanding of the role of triggering events in massive star formation.

scholarly journals The High Mass X-ray binaries in star-forming galaxies

2018 ◽  
Vol 14 (S346) ◽  
pp. 332-336
Author(s):  
M. Celeste Artale ◽  
Nicola Giacobbo ◽  
Michela Mapelli ◽  
Paolo Esposito
Keyword(s):  
Luminosity Function ◽  
High Mass ◽  
Population Synthesis ◽  
Host Galaxies ◽  
X Ray ◽  
Star Forming ◽  
Star Formation In Galaxies ◽  
Binary Evolution ◽  
X Ray Binaries ◽  
The Universe

AbstractThe high mass X-ray binaries (HMXBs) provide an exciting framework to investigate the evolution of massive stars and the processes behind binary evolution. HMXBs have shown to be good tracers of recent star formation in galaxies and might be important feedback sources at early stages of the Universe. Furthermore, HMXBs are likely the progenitors of gravitational wave sources (BH–BH or BH–NS binaries that may merge producing gravitational waves). In this work, we investigate the nature and properties of HMXB population in star-forming galaxies. We combine the results from the population synthesis model MOBSE (Giacobbo & Mapelli 2018a) together with galaxy catalogs from EAGLE simulation (Schaye et al. 2015). Therefore, this method describes the HMXBs within their host galaxies in a self-consistent way. We compute the X-ray luminosity function (XLF) of HMXBs in star-forming galaxies, showing that this methodology matches the main features of the observed XLF.

scholarly journals Massive Stars at High Redshifts

2007 ◽  
Vol 3 (S250) ◽  
pp. 415-428
Author(s):  
Max Pettini
Keyword(s):  
Massive Stars ◽  
High Redshift ◽  
Mass Function ◽  
Initial Mass Function ◽  
Stellar Spectra ◽  
Star Forming ◽  
Star Forming Regions ◽  
Look Ahead ◽  
Low Metallicity ◽  
High Redshift Universe

AbstractThe five years that have passed since the last IAU Symposium devoted to massive stars have seen a veritable explosion of data on the high redshift universe. The tools developed to study massive stars in nearby galaxies are finding increasing application to the analysis of the spectra of star-forming regions at redshifts as high as z = 7. In this brief review, I consider three topics of relevance to this symposium: the determination of the metallicities of galaxies at high redshifts from consideration of their ultraviolet stellar spectra; constraints on the initial mass function of massive stars in galaxies at z = 2 − 3; and new clues to the nucleosynthesis of carbon and nitrogen in massive stars of low metallicity. The review concludes with a look ahead at some of the questions that may occupy us for the next five years (at least!).

scholarly journals Blowin' in the wind: both ‘negative’ and ‘positive’ feedback in an outflowing quasar at z∼1.6

2014 ◽  
Vol 10 (S309) ◽  
pp. 239-242
Author(s):  
Giovanni Cresci
Keyword(s):  
Star Formation ◽  
Positive Feedback ◽  
Near Infrared ◽  
Host Galaxy ◽  
Narrow Component ◽  
Massive Galaxies ◽  
Star Forming ◽  
Star Forming Regions ◽  
Integral Field Spectroscopy ◽  
Outflow Rate

AbstractQuasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation, preventing massive galaxies to over-grow and producing the red colors of ellipticals. On the other hand, some models are also requiring ‘positive’ AGN feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively-driven winds are available. We present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z=1.59 QSO, in which we clearly resolve a fast (1500 km/s) and extended (up to 13 kpc from the black hole) outflow in the [OIII] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of Hα emission and the rest frame U band flux show that the outflow position lies in the center of an empty cavity surrounded by star forming regions on its edge. The outflow is therefore removing the gas from the host galaxy (‘negative feedback’), but also triggering star formation by outflow induced pressure at the edges (‘positive feedback’). XID2028 represents the first example of a host galaxy showing both types of feedback simultaneously at work.

scholarly journals No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations

2020 ◽  
Vol 498 (2) ◽  
pp. 2001-2017 ◽  
Author(s):  
Xiangcheng Ma ◽  
Eliot Quataert ◽  
Andrew Wetzel ◽  
Philip F Hopkins ◽  
Claude-André Faucher-Giguère ◽  
...  
Keyword(s):  
Large Fraction ◽  
High Mass ◽  
Population Synthesis ◽  
Single Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Sample Average ◽  
Dense Shell ◽  
Low Mass ◽  
Dust Attenuation

ABSTRACT We present the escape fraction of hydrogen ionizing photons (fesc) from a sample of 34 high-resolution cosmological zoom-in simulations of galaxies at z ≥ 5 in the Feedback in Realistic Environments project, post-processed with a Monte Carlo radiative transfer code for ionizing radiation. Our sample consists of 8500 haloes in Mvir ∼ 108–$10^{12}\, M_{\odot }$ (M* ∼ 104–$10^{10}\, M_{\odot }$) at z = 5–12. We find the sample average 〈fesc〉increases with halo mass for Mvir ∼ 108–$10^{9.5}\, M_{\odot }$, becomes nearly constant for 109.5–$10^{11}\, M_{\odot }$, and decreases at ${\gtrsim}10^{11}\, M_{\odot }$. Equivalently, 〈fesc〉 increases with stellar mass up to $M_{\ast }\sim 10^8\, M_{\odot }$ and decreases at higher masses. Even applying single-star stellar population synthesis models, we find a moderate 〈fesc〉 ∼ 0.2 for galaxies at $M_{\ast }\sim 10^8\, M_{\odot }$. Nearly half of the escaped ionizing photons come from stars 1–3 Myr old and the rest from stars 3–10 Myr old. Binaries only have a modest effect, boosting 〈fesc〉 by ∼25–35 per cent and the number of escaped photons by 60–80 per cent. Most leaked ionizing photons are from vigorously star-forming regions that usually contain a feedback-driven kpc-scale superbubble surrounded by a dense shell. The shell is forming stars while accelerated, so new stars formed earlier in the shell are already inside the shell. Young stars in the bubble and near the edge of the shell can fully ionize some low-column-density paths pre-cleared by feedback, allowing a large fraction of their ionizing photons to escape. The decrease of 〈fesc〉 at the high-mass end is due to dust attenuation, while at the low-mass end, 〈fesc〉 decreases owing to inefficient star formation and hence feedback. At fixed mass, 〈fesc〉 tends to increase with redshift. Although the absolute 〈fesc〉does not fully converge with resolution in our simulations, the mass- and redshift-dependence of 〈fesc〉 is likely robust. Our simulations produce sufficient ionizing photons for cosmic reionization.

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.

scholarly journals Resolved Spectroscopy of Gravitationally Lensed Galaxies at z≃2

2014 ◽  
Vol 10 (S309) ◽  
pp. 247-250
Author(s):  
Tucker Jones
Keyword(s):  
Gas Phase ◽  
Gravitational Lensing ◽  
Gravitational Interaction ◽  
Interstellar Gas ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
Integral Field Spectroscopy ◽  
Isolated Galaxies ◽  
Spatially Resolved Spectroscopy

AbstractSpatially resolved spectroscopy is even more powerful when combined with magnification by gravitational lensing. I discuss observations of lensed galaxies at z≃2 with spatial resolution reaching 100 parsecs. Near-IR integral field spectroscopy reveals the kinematics, distribution and physical properties of star forming regions, and gas-phase metallicity gradients. Roughly two thirds of observed galaxies are isolated systems with coherent velocity fields, large velocity dispersion, multiple giant star-forming regions, and negative gas-phase metallicity gradients, suggestive of inside-out growth in gravitationally unstable disks. The remainder are undergoing mergers and have shallower metallicity gradients, indicating mixing of the interstellar gas via gravitational interaction. The metallicity gradients in isolated galaxies are consistent with simulations using standard feedback prescriptions, whereas simulations with enhanced feedback predict shallower gradients. These measurements therefore constrain the growth of galaxies from mergers and star formation as well as the regulatory feedback.

scholarly journals Radial Infall onto a Massive Molecular Filament

2015 ◽  
Vol 11 (A29B) ◽  
pp. 711-713
Author(s):  
Cara Battersby ◽  
Philip C. Myers ◽  
Yancy L. Shirley ◽  
Eric Keto ◽  
Helen Kirk
Keyword(s):  
Large Scale ◽  
Massive Star ◽  
Massive Stars ◽  
Physical Structure ◽  
Line Profiles ◽  
Dark Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
Current Mass ◽  
Structure Density

AbstractThe newly discovered Massive Molecular Filament (MMF) G32.02+0.05 (~ 70 pc long, 105 M⊙) has been shaped and compressed by older generations of massive stars. The similarity of this filament in physical structure (density profile, temperature) to much smaller star-forming filaments, suggests that the mechanism to form such filaments may be a universal process. The densest portion of the filament, apparent as an Infrared Dark Cloud (IRDC) shows a range of massive star formation signatures throughout. We investigate the kinematics in this filament and find widespread inverse P cygni asymmetric line profiles. These line asymmetries are interpreted as a signature of large-scale radial collapse. Using line asymmetries observed with optically thick HCO+ (1-0) and optically thin H13CO+ (1-0) across a range of massive star forming regions in the filament, we estimate the global radial infall rate of the filament to range from a few 100 to a few 1000 M⊙ Myr−1 pc−1. At its current infall rate the densest portions of the cloud will more than double their current mass within a Myr.

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