scholarly journals The massive star-forming region Cygnus OB2

2009 ◽  
Vol 5 (S266) ◽  
pp. 551-554
Author(s):  
N. J. Wright ◽  
J. J. Drake
Keyword(s):  
Massive Star ◽  
Near Infrared ◽  
Protoplanetary Disks ◽  
Mass Function ◽  
Initial Mass Function ◽  
Point Sources ◽  
Older Population ◽  
X Ray ◽  
Ob Stars ◽  
Star Forming

AbstractWe present results from a catalogue of 1696 X-ray point sources detected in the massive star-forming region Cygnus OB2, the majority of which have optical or near-infrared associations. We derive ages of 3.5 and 5.25 Myr for the stellar populations in our two fields, in agreement with recent studies that suggest that the central 1–3 Myr-old OB association is surrounded and contaminated by an older population with an age of 5–10 Myr. The fraction of sources with protoplanetary disks, as traced by K-band excesses, is unusually low. Although this has previously been interpreted as due to the influence of the large number of OB stars in Cyg OB2, contamination from an older population of stars in the region could also be responsible. An initial mass function is derived and found to have a slope of Γ = −1.27, in agreement with the canonical value. Finally, we introduce the recently approved Chandra Cygnus OB2 Legacy Survey that will image a 1 square degree area of the Cygnus OB2 association to a depth of 120~ks, likely detecting ~ 10 000 stellar X-ray sources.

The Initial Mass Function of a Massive Star‐forming Region W51

2000 ◽  
Vol 543 (2) ◽  
pp. 799-821 ◽  
Author(s):  
Shin‐ichiro Okumura ◽  
Atsushi Mori ◽  
Eiji Nishihara ◽  
Etsuji Watanabe ◽  
Takuya Yamashita
Keyword(s):  
Massive Star ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Star Forming

scholarly journals Candidate X-Ray-emitting OB Stars in MYStIX Massive Star-forming Regions

2017 ◽  
Vol 838 (1) ◽  
pp. 61 ◽  
Author(s):  
Matthew S. Povich ◽  
Heather A. Busk ◽  
Eric D. Feigelson ◽  
Leisa K. Townsley ◽  
Michael A. Kuhn
Keyword(s):  
Massive Star ◽  
X Ray ◽  
Ob Stars ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals The massive star Initial Mass function

2003 ◽  
Vol 212 ◽  
pp. 642-651 ◽  
Author(s):  
Daniel Schaerer
Keyword(s):  
Massive Star ◽  
Current Knowledge ◽  
Star Clusters ◽  
Mass Function ◽  
Initial Mass Function ◽  
H Ii Regions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Super Star Clusters ◽  
The Imf

We review our current knowledge on the IMF in nearby environments, massive star forming regions, super star clusters, starbursts and alike objects from studies of integrated light, and discuss the various techniques used to constrain the IMF. In most cases, including UV-optical studies of stellar features and optical-IR analysis of nebular emission, the data is found to be compatible with a ‘universal’ Salpeter-like IMF with a high upper mass cut-off over a large metallicity range. In contrast, near-IR observations of nuclear starbursts and LIRG show indications of a lowerMupand/or a steeper IMF slope, for which no alternate explanation has yet been found. Also, dynamical mass measurements of seven super star clusters provide so far no simple picture of the IMF. Finally, we present recent results of a direct stellar probe of the upper end of the IMF in metal-rich H ii regions, showing no deficiency of massive stars at high metallicity, and determining a lower limit ofMup≳ 60 – 90 M⊙.

scholarly journals Ultraviolet photo-ionisation in far-infrared selected sources

2019 ◽  
Vol 627 ◽  
pp. A93 ◽  
Author(s):  
S. J. Curran ◽  
S. W. Duchesne
Keyword(s):  
Massive Stars ◽  
Neutral Hydrogen ◽  
Far Infrared ◽  
Theoretical Models ◽  
Mass Function ◽  
Critical Value ◽  
Initial Mass Function ◽  
X Ray ◽  
Star Forming ◽  
Rule Out

It has been reported that there is a deficit of stellar heated dust, as evident from the lack of far-infrared (FIR) emission, in sources within the Herschel-SPIRE sample with X-ray luminosities exceeding a critical value of LX ∼ 1037 W. Such a scenario would be consistent with the suppression of star formation by the AGN, required by current theoretical models. Since absorption of the 21 cm transition of neutral hydrogen (H I), which traces the star-forming reservoir, also exhibits a critical value in the ultraviolet band (above ionising photon rates of Q ≈ 3 × 1056 s−1), we test the SPIRE sample for the incidence of the detection of 250 μm emission with Q. The highest value at which FIR emission is detected above the SPIRE confusion limit is Q = 8.9 × 1057 s−1, which is ≈30 times that for the H I, with no critical value apparent. Since complete ionisation of the neutral atomic gas is expected at Q ≳ 3 × 1056 s−1, this may suggest that much of the FIR must arise from heating of the dust by the AGN. However, integrating the ionising photon rate of each star over the initial mass function, we cannot rule out that the high observed ionising photon rates are due to a population of hot, massive stars.

scholarly journals Massive star populations in Lyman break galaxies

2003 ◽  
Vol 212 ◽  
pp. 671-680 ◽  
Author(s):  
Max Pettini ◽  
Samantha A. Rix ◽  
Charles C. Steidel ◽  
Alice E. Shapley ◽  
Kurt L. Adelberger
Keyword(s):  
Near Infrared ◽  
Massive Stars ◽  
Current Knowledge ◽  
Mass Function ◽  
Initial Mass Function ◽  
Chemical Abundances ◽  
Star Forming ◽  
Lyman Break Galaxies ◽  
New Evidence ◽  
The Universe

Massive stars provide most of our current knowledge of the first star forming galaxies in the universe via their ultraviolet and optical spectra redshifted into the visible and near-infrared bands. Here I briefly review the growing body of data on these early stellar populations from which star formation rates, the initial mass function, chemical abundances, ages, and dust reddenings are being deduced. New evidence also shows the dramatic impact which massive stars have on their galactic and intergalactic environments.

scholarly journals A deep dive into NGC 604 with Gemini/NIRI imaging

2009 ◽  
Vol 5 (S266) ◽  
pp. 391-394
Author(s):  
Cecilia Fariña ◽  
Guillermo L. Bosch ◽  
Rodolfo R. Barbá
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Near Infrared ◽  
Mass Function ◽  
Initial Mass Function ◽  
Infrared Study ◽  
Infrared Excess ◽  
Deep Dive ◽  
Physical Conditions ◽  
First Results

AbstractThe giant Hii region NGC 604 constitutes a complex and rich population to study in detail many aspects of massive star formation, such as their environments and physical conditions, the evolutionary processes involved, the initial mass function for massive stars and star-formation rates, among many others. Here, we present our first results of a near-infrared study of NGC 604 performed with NIRI images obtained with Gemini North. Based on deep JHK photometry, 164 sources showing infrared excess were detected, pointing to the places where we should look for star-formation processes currently taking place. In addition, the color–color diagram reveals a great number of objects that could be giant/supergiant stars or unresolved, small, tight clusters. An extinction map obtained based on narrow-band images is also shown.

scholarly journals Very Low-Luminosity Objects in Star-Forming Regions

1998 ◽  
Vol 11 (1) ◽  
pp. 423-424
Author(s):  
Motohide Tamura ◽  
Yoichi Itoh ◽  
Yumiko Oasa ◽  
Alan Tokunaga ◽  
Koji Sugitani
Keyword(s):  
Brown Dwarfs ◽  
Mass Function ◽  
T Tauri Stars ◽  
Initial Mass Function ◽  
Formation Mechanisms ◽  
Star Forming ◽  
Star Forming Regions ◽  
T Tauri ◽  
Low Mass ◽  
Stellar Sources

Abstract In order to tackle the problems of low-mass end of the initial mass function (IMF) in star-forming regions and the formation mechanisms of brown dwarfs, we have conducted deep infrared surveys of nearby molecular clouds. We have found a significant population of very low-luminosity sources with IR excesses in the Taurus cloud and the Chamaeleon cloud core regions whose extinction corrected J magnitudes are 3 to 8 mag fainter than those of typical T Tauri stars in the same cloud. Some of them are associated with even fainter companions. Follow-up IR spectroscopy has confirmed for the selected sources that their photospheric temperature is around 2000 to 3000 K. Thus, these very low-luminosity young stellar sources are most likely very low-mass T Tauri stars, and some of them might even be young brown dwarfs.

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 The young star cluster NGC 2362: low-mass population and initial mass function from a Chandra X-ray observation

2006 ◽  
Vol 460 (1) ◽  
pp. 133-144 ◽  
Author(s):  
F. Damiani ◽  
G. Micela ◽  
S. Sciortino ◽  
N. Huélamo ◽  
A. Moitinho ◽  
...  
Keyword(s):  
Mass Function ◽  
Young Star ◽  
Star Cluster ◽  
Initial Mass Function ◽  
Initial Mass ◽  
X Ray ◽  
Low Mass
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