scholarly journals A Census of Diverse Environments in Star Forming Regions: Where Do Massive Stars Form?

2014 ◽  
Author(s):  
William Dirienzo
2002 ◽  
Vol 12 ◽  
pp. 143-145 ◽  
Author(s):  
Lee G. Mundy ◽  
Friedrich Wyrowski ◽  
Sarah Watt

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.


2007 ◽  
Vol 3 (S250) ◽  
pp. 415-428
Author(s):  
Max Pettini

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!).


2021 ◽  
Vol 503 (4) ◽  
pp. 6112-6135
Author(s):  
Peter Senchyna ◽  
Daniel P Stark ◽  
Stéphane Charlot ◽  
Jacopo Chevallard ◽  
Gustavo Bruzual ◽  
...  

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.


2002 ◽  
Vol 206 ◽  
pp. 226-233 ◽  
Author(s):  
Jesús Martín-Pintado

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.


2015 ◽  
Vol 11 (A29B) ◽  
pp. 711-713
Author(s):  
Cara Battersby ◽  
Philip C. Myers ◽  
Yancy L. Shirley ◽  
Eric Keto ◽  
Helen Kirk

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.


2009 ◽  
Vol 5 (S266) ◽  
pp. 377-379
Author(s):  
Srabani Datta

AbstractObservations show that massive stars always form in clusters or associations, and that the most massive stars form in the dense cores of large clusters. This suggests that accretion processes in cluster cores may be responsible for the formation of stars. In addition, young stellar clusters have been found to contain subclusters, so that star formation can be seen to be a hierarchical process that involves clustering on a range of scales. In this paper, we propose a fractal model of the parental molecular cloud, namely that of the Julia set given by f(z) = z2 + c, where z and c are complex numbers and c = −0.745430 + 0.113008i, to explain this phenomenon and the associated complex structures seen in star-forming regions.


2014 ◽  
Vol 10 (S313) ◽  
pp. 370-373
Author(s):  
I. F. Mirabel ◽  
S. Chaty ◽  
L. F. Rodríguez ◽  
M. Sauvage

AbstractTheoretical and observational work show that jets from AGN can trigger star formation. However, in the Milky Way the first -and so far- only clear case of relativistic jets inducing star formation has been found in the surroundings of the microquasar GRS 1915+105. Here we summarize the multiwavelength observations of two compact star formation IRAS sources axisymmetrically located and aligned with the position angle of the sub-arcsec relativistic jets from the stellar black hole binary GRS 1915+105 (Mirabel & Rodríguez 1994). The observations of these two star forming regions at centimeter (Mirabel & Rodríguez 1998), millimeter and infrared (Chaty et al. 2001) wavelengths had suggested -despite the large uncertainties in the distances a decade ago- that the jets from GRS 1915+105 are triggering along the radio jet axis the formation of massive stars in a radio lobe of bow shock structure. Recently, Reid et al. (2014) found that the jet source and the IRAS sources are at the same distance, enhancing the evidence for the physical association between the jets from GRS 1915+105 and star formation in the IRAS sources. We conclude that as jets from AGN, jets from microquasars can trigger the formation of massive stars, but at distances of a few tens of parsecs. Although star formation induced by microquasar jets may not be statistically significant in the Milky Way, jets from stellar black holes may have been important to trigger star formation during the re-ionization epoch of the universe (Mirabel et al. 2011). Because of the relative proximity of GRS 1915+105 and the associated star forming regions, they may serve as a nearby laboratory to gain insight into the physics of jet-trigger star formation elsewhere in the universe.


2020 ◽  
Vol 500 (1) ◽  
pp. 962-975
Author(s):  
K Kouroumpatzakis ◽  
A Zezas ◽  
A Wolter ◽  
A Fruscione ◽  
K Anastasopoulou ◽  
...  

ABSTRACT We present a systematic study of the metallicity variations within the collisional ring galaxy NGC 922 based on long-slit optical spectroscopic observations. We find a metallicity difference between star-forming regions in the bulge and the ring, with metallicities ranging from almost solar to significantly sub-solar ($\rm {[12+\log (O/H)]\sim 8.2}$). We detect $\rm{He\,{\small I}}$ emission in all the studied regions of the bulge and the ring, indicating ionization from massive stars associated with recent (<10 Myr) star formation, in agreement with the presence of very young star clusters. We find an anticorrelation between the X-ray luminosity and metallicity of the sub-galactic regions of NGC 922. The different regions have similar stellar population ages, leaving metallicity as the main driver of the anticorrelation. The dependence of the X-ray emission of the different regions in NGC 922 on metallicity is in agreement with similar studies of the integrated X-ray output of galaxies and predictions from X-ray binary population models.


2020 ◽  
Vol 891 (2) ◽  
pp. 113
Author(s):  
David Rebolledo ◽  
Andrés E. Guzmán ◽  
Yanett Contreras ◽  
Guido Garay ◽  
S.-N. X. Medina ◽  
...  

2016 ◽  
Vol 12 (S329) ◽  
pp. 292-296
Author(s):  
Paul A. Crowther ◽  
Saida M. Caballero-Nieves ◽  
Norberto Castro ◽  
Christopher J. Evans

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.


Sign in / Sign up

Export Citation Format

Share Document