scholarly journals Massive stars and the creation of our Galactic Center

2003 ◽  
Vol 212 ◽  
pp. 487-496 ◽  
Author(s):  
Donald F. Figer
Keyword(s):  
Star Formation ◽  
Galactic Center ◽  
Massive Stars ◽  
Formation Rate ◽  
Stellar Content ◽  
The Past ◽  
Luminosity Functions ◽  
Region I ◽  
The Galaxy ◽  
Massive Clusters

Our Galactic Center hosts over 10% of the known massive stars in the Galaxy. The majority of these stars are located in three particularly massive clusters that formed within the past 5 Myr. While these clusters are extraordinary, their formation repesents about half of the total inferred star-formation rate in the Galactic Center. There is mounting evidence that the clusters are just present-day examples of the hundreds of such similar clusters that must have been created in the past, and whose stars now comprise the bulk of all stars seen in the region. I discuss the massive stellar content in the Galactic Center and present a new analysis that suggests that effects of continuous star-formation in the Galactic Center can be seen in the observed luminosity functions newly-obtained HST-nicmos and Gemini-ao data.

scholarly journals Massive stars in the young cluster VVV CL074

2019 ◽  
Vol 627 ◽  
pp. A170 ◽  
Author(s):  
F. Martins ◽  
A.-N. Chené ◽  
J.-C. Bouret ◽  
J. Borissova ◽  
J. Groh ◽  
...  
Keyword(s):  
Massive Star ◽  
Galactic Center ◽  
Massive Stars ◽  
Stellar Content ◽  
Integral Field Spectroscopy ◽  
The Galaxy ◽  
Infrared Spectral ◽  
Band Spectra ◽  
Stellar Properties ◽  
Massive Clusters

Context. The evolution of massive stars is not fully constrained. Studies of young massive clusters hosting various populations of massive stars can help refine our understanding of the life and fate of massive stars. Aims. In this context, our goal is to study the massive stellar content of the young massive cluster VVV CL074. Methods. We obtained K-band spectroscopy of the brightest cluster members in order to identify the massive star population. We also determined the stellar properties of the cluster’s massive stars to better quantify the evolutionary sequences linking different types of massive stars. We collected integral field spectroscopy of selected fields in the cluster VVV CL074 with SINFONI on the ESO/VLT. We performed a spectral classification based on the K-band spectra and comparison to infrared spectral atlases. We determined the stellar parameters of the massive stars from analysis with atmosphere models computed with the code CMFGEN. Results. We uncover a population of 25 early-type (OB and Wolf–Rayet) stars, 19 being newly discovered by our observations out of which 15 are likely cluster members. The cluster’s spectrophotometric distance is 10.2 ± 1.6 kpc, placing it close to the intersection of the galactic bar and the Norma arm, beyond the galactic center. This makes VVV CL074 one the farthest young massive clusters identified so far. Among the massive stars population, three objects are Wolf–Rayet stars, the remaining are O and B stars. From the Hertzsprung–Russell diagram we find that most stars have an age between 3 and 6 Myr according to the Geneva evolutionary tracks. WN8 and WC8-9 stars are the descendants of stars with initial masses between 40 and 60 M⊙. The massive star population of VVV CL074 is very similar to that of the cluster DBS2003-179 and to a lesser extent to that of the Quintuplet cluster, indicating the same age. The central cluster of the Galaxy is ∼3 Myr older. From the comparison of the massive stars populations in these four clusters, one concludes that galactic stars with an initial mass in the range 40–60 M⊙ likely go through a WN8-9 phase.

scholarly journals Super star clusters in the Galactic Center as revealed by HST-NICMOS

1999 ◽  
Vol 193 ◽  
pp. 459-469
Author(s):  
Donald F. Figer ◽  
Sungsoo S. Kim ◽  
Mark Morris ◽  
Eugene Serabyn
Keyword(s):  
Main Sequence ◽  
Local Group ◽  
Galactic Center ◽  
Formation Rate ◽  
Star Clusters ◽  
Initial Mass Function ◽  
Stellar Content ◽  
Multiple Star ◽  
Super Star Clusters ◽  
Massive Clusters

The three massive clusters in the Galactic Center are not only the most massive young clusters in the Galaxy, but they harbor more Wolf-Rayet stars than any other starburst region in the Local Group. An understanding of their stellar content will be valuable for extending models to starburst regions in other galaxies. We present HST-NICMOS images, luminosity functions, and color-magnitude diagrams of two of these: the Quintuplet and Arches clusters. The images allow the detection of stars over 6 magnitudes fainter than ever before and reveal previously undetected multiple star systems. For the first time, we clearly identify the main sequence in the Quintuplet cluster, and we extend earlier detections of the main sequence in the Arches cluster to Minitial < 10 M⊙. We estimate that the Arches cluster has an initial mass function slope which is greater than the Salpeter value. Given their stellar content, the Galactic Center clusters provide both the best nearby examples of super star clusters and the best nearby locale in which to investigate WR phenomena in starburst galaxies and galactic nuclei. We discuss the content of the Galactic Center clusters, with a particular emphasis on how they compare to other massive clusters of the local group. We expect that many of the massive stars in the Galactic Center will soon evolve to become WR stars, and eventually become supernovae at a rate of ∼ 1 per 20 000 years for the next several Myr. We note that our preliminary N-body simulations suggest that such dense clusters are short-lived in the strong tidal field of the Galactic Center, consistent with the fact that no older dense clusters are seen in the central 50 pc. This implies a star formation rate of 5(10−3) M⊙ yr−1 in the Galactic Center.

scholarly journals Young Massive Clusters

2007 ◽  
Vol 3 (S250) ◽  
pp. 247-256 ◽  
Author(s):  
Donald F. Figer
Keyword(s):  
Stellar Evolution ◽  
Massive Stars ◽  
Stellar Clusters ◽  
Infrared Observations ◽  
The Past ◽  
The Galaxy ◽  
The Masses ◽  
Near Future ◽  
Massive Clusters

AbstractOver the past ten years, there has been a revolution in our understanding of massive young stellar clusters in the Galaxy. Initially, there were no known examples having masses >104, yet we now know that there are at least a half dozen such clusters in the Galaxy. In all but one case, the masses have been determined through infrared observations. Several had been identified as clusters long ago, but their massive natures were only recently determined. Presumably, we are just scratching the surface, and we might look forward to having statistically significant samples of coeval massive stars at all important stages of stellar evolution in the near future. I review the efforts that have led to this dramatic turn of events and the growing sample of young massive clusters in the Galaxy.

scholarly journals The Herschel view of the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 1-14
Author(s):  
John Bally ◽  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Galactic Center ◽  
Galactic Plane ◽  
Formation Rate ◽  
Asymmetric Distribution ◽  
The Galaxy ◽  
Sgr A ◽  
Almost All

AbstractThe 3.5 meter diameter Herschel Space Observatory conducted a ∼720 square-degree survey of the Galactic plane, the Herschel Galactic plane survey (Hi-GAL). These data provide the most sensitive and highest resolution observations of the far-IR to sub-mm continuum from the central molecular zone (CMZ) at λ = 70, 160, 250, 350, and 500 μm obtained to date. Hi-GAL can be used to map the distributions of temperature and column density of dust in CMZ clouds, warm dust in Hii regions, and identify highly embedded massive protostars and clusters and the dusty shells ejected by supergiant stars. These data enable classification of sources and re-evaluation of the current and recent star-formation rate in the CMZ. The outer CMZ beyond |l| = 0.9 degrees (Rgal > 130 pc) contains most of the dense (n > 104 cm−3 gas in the Galaxy but supports very little star formation. The Hi-GAL and Spitzer data show that almost all star formation occurs in clouds moving on x2 orbits at Rgal < 100 pc. While the 106 M⊙ Sgr B2 complex, the 50 km s−1 cloud near Sgr A, and the Sgr C region are forming clusters of massive stars, other clouds are relatively inactive star formers, despite their high densities, large masses, and compact sizes. The asymmetric distribution of dense gas about Sgr A* on degree scales (most dense CMZ gas and dust is at positive Galactic longitudes and positive VLSR) and compact 24 μm sources (most are at negative longitudes) may indicate that eposidic mini-starbursts occasionally ‘blow-out’ a portion of the gas on these x2 orbits. The resulting massive-star feedback may fuel the compact 30 pc scale Galactic center bubble associated with the Arches and Quintuplet clusters, the several hundred pc scale Sofue-Handa lobe, and the kpc-scale Fermi/LAT bubble, making it the largest ‘superbubble’ in the Galaxy. A consequence of this model is that in our Galaxy, instead of the supermassive black hole (SMBH) limiting star formation, star formation may limit the growth of the SMBH.

scholarly journals Feeding and feedback in nearby AGN – comparison with the Milky Way center

2013 ◽  
Vol 9 (S303) ◽  
pp. 354-363 ◽  
Author(s):  
T. Storchi-Bergmann
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Galactic Center ◽  
Formation Rate ◽  
Activity Cycle ◽  
Nuclear Region ◽  
Nuclear Activity ◽  
The Galaxy ◽  
Mass Outflow ◽  
Sgr A

AbstractI discuss feeding and feedback processes observed in the inner few hundred parsecs of nearby active galaxies using integral field spectroscopy at spatial resolutions of a few to tens of parsecs. Signatures of feedback include outflows from the nucleus with velocities ranging from 200 to 1000 km s−1, with mass outflow rates between 0.5 and a few M⊙ yr−1. Signatures of feeding include the observation of gas inflows along nuclear spirals and filaments, with velocities ranging from 50 to 100 km s−1 and mass flow rates from 0.1 to ∼1 M⊙ yr−1. These rates are 2–3 orders of magnitude larger than the mass accretion rate to the supermassive black hole (SMBH). These inflows can thus lead, during less than one activity cycle, to the accumulation of enough gas in the inner few hundred parsecs, to trigger the formation of new stars, leading to the growth of the galaxy bulge. Young to intermediate age stars have indeed been found in circumnuclear rings around a number of Active Galactic Nuclei (AGN). In particular, one of these rings, with radius of ≈ 100 pc is observed in the Seyfert 2 galaxy NGC 1068, and is associated to an off-centered molecular ring, very similar to that observed in the Milky Way (MW). On the basis of an evolutionary scenario in which gas falling into the nuclear region triggers star formation followed by the triggering of nuclear activity, we speculate that, in the case of the MW, molecular gas has already accumulated within the inner ≈ 100 pc to trigger the formation of new stars, as supported by the presence of blue stars close to the galactic center. A possible increase in the star-formation rate in the nuclear region will then be followed, probably tens of millions of years later, by the triggering of nuclear activity in Sgr A*.

scholarly journals Luminous Stellar Content of the Galaxy: Inferences from Radio and Infrared Data

1986 ◽  
Vol 116 ◽  
pp. 479-495
Author(s):  
P. G. Mezger
Keyword(s):  
Star Formation ◽  
Reasonable Agreement ◽  
Star Formation Rate ◽  
Galactic Disk ◽  
Formation Rate ◽  
Stellar Content ◽  
Lyman Continuum ◽  
The Galaxy ◽  
Low Mass ◽  
Infrared Data

Lyman continuum (Lyc) photon production rates can be estimated from radio free-free emission and used to estimate the star formation rate (SFR) of 0 stars. If this SFR is linked to the total SFR through a constant IMF (m ≳0.1 m⊙) one derives for our Galaxy a present-day SFR of ∼10 m⊙ yr−1, which is close to the average SFR over the age of the galactic disk. This is difficult to reconcile with a formation law of the form SFR φ∝Mgask with k>0 which yields SFRs which decrease with time. Even more severe is the fact that the mass distribution of the galactic disk cannot be reproduced by the present-day SFR with a constant IMF. Bimodal star formation, however, reduces the rate at which matter is permanently locked up in low mass and dead stars by nearly a factor of three, and gets reasonable agreement between the present-day distribution of stellar mass and lock-up rate. Bimodal star formation means that stars with m >0.1 m⊙ form in the interarm region while in spiral arms induced star formation produces only stars with m >mc ∼2–3 m⊙.

scholarly journals One Hundred 30 Dors?

2007 ◽  
Vol 3 (S250) ◽  
pp. 307-312 ◽  
Author(s):  
M. M. Hanson ◽  
B. Popescu
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Star Formation Rate ◽  
Open Cluster ◽  
Formation Rate ◽  
Mass Function ◽  
Open Clusters ◽  
The Galaxy ◽  
Massive Clusters ◽  
Image Simulations

AbstractThere are a few ways to estimate the number of massive open clusters expected in the disk of the Milky Way, such as the total star formation rate of the Galaxy, or the open cluster mass function extrapolated to include the entire Galaxy. Surprisingly, they give similar predictions: the Milky Way should contain about 100 clusters as massive as 30 Doradus. Are we seeing them? We look closely at these predictions and compare them to what has been found so far in our Galaxy. We present sophisticated image simulations our group is developing to estimate the selection biases faced by current infrared searches for these massive clusters.

scholarly journals A Stellar Content Study of NGC 2403 with the automated Plate Scanner

1986 ◽  
Vol 116 ◽  
pp. 83-84
Author(s):  
Thomas R. Manley
Keyword(s):  
Star Formation ◽  
Massive Stars ◽  
Stellar Content ◽  
Photometric Calibration ◽  
Luminosity Functions ◽  
Magnitude Diagram

In this poster we illustrate how the Minnesota Automated Plate Scanner (APS) is being used to study the luminous stellar content of NGC 2403. Presented are a brief description of the APS, examples of photometric calibration, separation of stellar and non-stellar images, and a preliminary color-magnitude diagram. The eventual goal is to study the evolution of massive stars via color-magnitude diagrams, luminosity functions and star formation rates.

scholarly journals Retrieving the stellar content in distant starbursts

2011 ◽  
Vol 7 (S284) ◽  
pp. 218-220
Author(s):  
Myriam A. Rodrigues ◽  
François Hammer ◽  
Mathieu Puech
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Spectral Features ◽  
Stellar Content ◽  
Distant Galaxies ◽  
Stellar Masses

AbstractIn starburst galaxies, the light emitted by the young and massive stars dominates the photon budget along most of the SED and hides the old and intermediate stellar populations. The fraction of old stars and the stellar mass are systematically underestimated by current methods (Wuyts et al. (2009)). We have implemented a new method to retrieve stellar masses and stellar populations in distant galaxies from photometry and spectral features. The method uses a complex SFH description and a new constraint has been introduced: the star-formation rate (SFR).

scholarly journals Star Formation in the Central Molecular Zone of the Milky Way

2010 ◽  
Vol 6 (S270) ◽  
pp. 359-362
Author(s):  
Sungsoo S. Kim ◽  
Takayuki R. Saitoh ◽  
Myoungwon Jeon ◽  
David Merritt ◽  
Donald F. Figer ◽  
...  
Keyword(s):  
Star Formation ◽  
Galactic Center ◽  
Galactic Disk ◽  
Formation Rate ◽  
Infrared Observations ◽  
Recent Estimate ◽  
The Galaxy ◽  
Self Gravity ◽  
Supernova Feedback

AbstractGas materials in the inner Galactic disk continuously migrate toward the Galactic center (GC) due to interactions with the bar potential, magnetic fields, stars, and other gaseous materials. Those in forms of molecules appear to accumulate around 200 pc from the center (the central molecular zone, CMZ) to form stars there and further inside. The bar potential in the GC is thought to be responsible for such accumulation of molecules and subsequent star formation, which is believed to have been continuous throughout the lifetime of the Galaxy. We present 3-D hydrodynamic simulations of the CMZ that consider self-gravity, radiative cooling, and supernova feedback, and discuss the efficiency and role of the star formation in that region. We find that the gas accumulated in the CMZ by a bar potential of the inner bulge effectively turns into stars, supporting the idea that the stellar cusp inside the central 200 pc is a result of the sustained star formation in the CMZ. The obtained star formation rate in the CMZ, 0.03–0.1 M⊙, is consistent with the recent estimate based on the mid-infrared observations by Yusef-Zadeh et al. (2009).

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