scholarly journals Stars and brown dwarfs, spatial distribution, multiplicity, X-rays, discs, and the complete mass function of the σ Orionis cluster

2009 ◽  
Author(s):  
José A. Caballero ◽  
Eric Stempels
Keyword(s):  
Spatial Distribution ◽  
Brown Dwarfs ◽  
Mass Function ◽  
X Rays

scholarly journals The Substellar Members of the Pleiades

2003 ◽  
Vol 211 ◽  
pp. 181-182
Author(s):  
Paul D. Dobbie ◽  
Richard F. Jameson ◽  
Samantha L. Osborne ◽  
Simon T. Hodgkin ◽  
David J. Pinfield
Keyword(s):  
Dark Matter ◽  
Spatial Distribution ◽  
Power Law ◽  
Spatial Model ◽  
Total Mass ◽  
Brown Dwarfs ◽  
Mass Function ◽  
Core Radius ◽  
Brown Dwarf ◽  
Limited Sample

We have compiled the largest magnitude limited sample of candidate substellar Pleiads to date. We fit King profiles to their spatial distribution to determine the Pleiades brown dwarf core radius to be Subsequently we have used our improved spatial model to place stringent limits on the shape of the cluster mass function across and below the stellar/substellar regime. We find this to be a power law with index α = 0.41±0.08 (0.3M⊙ ≥M≥ 0.035M⊙). Extrapolation of this mass function to M= 0.012M⊙ indicates that brown dwarfs contribute only ~ 2% to the total mass of the cluster hence we conclude that brown dwarfs do not contribute significantly to disk dark matter.

scholarly journals 6.12. Microlensing and dynamics of the Galactic bulge

1998 ◽  
Vol 184 ◽  
pp. 285-286
Author(s):  
H.S. Zhao
Keyword(s):  
Spatial Distribution ◽  
Brown Dwarfs ◽  
Mass Function ◽  
Dynamical Model ◽  
Galactic Bulge ◽  
Galactic Disc

Microlensing (μ—lensing) towards the bulge started out as a unique technique of detecting dark objects in the Galactic disc (brown dwarfs) by measuring a rare transient brightening of one star among millions of stars in the Galactic bulge (Paczyński 1991). More than 200 events have been detected towards the Bulge since 1993 by the DUO, MACHO, OGLE etc. survey teams. But where are the lenses? Are they truly dark objects or merely faint stars? I show the results on the mass function, spatial distribution and dynamics of these observed lenses based on a dynamical model of the Galactic bar.

scholarly journals Brown dwarfs in the Pleiades: spatial distribution and mass function

2002 ◽  
Vol 335 (3) ◽  
pp. 853-863 ◽  
Author(s):  
R. F. Jameson ◽  
P. D. Dobbie ◽  
S. T. Hodgkin ◽  
D. J. Pinfield
Keyword(s):  
Spatial Distribution ◽  
Brown Dwarfs ◽  
Mass Function

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 Observing Galaxy Clusters with eROSITA: Simulations

10.14311/1466 ◽  
2011 ◽  
Vol 51 (6) ◽  
Author(s):  
J. Hölzl ◽  
J. Wilms ◽  
I. Kreykenbohm ◽  
Ch. Schmid ◽  
Ch. Grossberger ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Dark Matter ◽  
Dark Energy ◽  
Galaxy Clusters ◽  
Cosmological Parameters ◽  
Mass Function ◽  
Angular Diameter ◽  
Monte Carlo Code ◽  
X Rays ◽  
Sky Survey

The eROSITA instrument on board the Russian Spectrum Roentgen Gamma spacecraft, which will be launched in 2013,will conduct an all sky survey in X-rays. A main objective of the survey is to observe galaxy clusters in order to constrain cosmological parameters and to obtain further knowledge about dark matter and dark energy. For the simulation of the eROSITA survey we present a Monte-Carlo code generating a mock catalogue of galaxy clusters distributed accordingto the mass function of [1]. The simulation generates the celestial coordinates as well as the cluster mass and redshift. From these parameters, the observed intensity and angular diameter are derived. These are used to scale Chandra cluster images as input for the survey-simulation.

scholarly journals Galactic starburst NGC 3603 from X-rays to radio

2003 ◽  
Vol 212 ◽  
pp. 515-522
Author(s):  
Anthony F.J. Moffat ◽  
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
X Rays ◽  
Stellar Content ◽  
Near Ir ◽  
The Galaxy ◽  
The Status ◽  
H Ii Region ◽  
Mass Segregation ◽  
Colliding Winds

While NGC 3603 is often quoted as the most massive visible Giant H ii Region in the Galaxy, there are other similar and even more massive regions now being found towards the inner Galaxy in the near-IR. Nevertheless, NGC 3603 still retains the status of clone to the dense core-object in 30 Dor, R 136 — but 7x closer and 49x less crowded! This paper summarizes the most recent findings concerning NGC 3603's color-magnitude diagram (CMD), initial mass function (IMF), mass segregation and stellar content — including its unusually luminous H-rich WNL members — down to its pre-main-sequence stars near the H-burning limit. Of special relevance are new high-resolution X-ray and radio images as related to merging/colliding winds and three massive proplyd-like objects. NGC 3603 is a somewhat younger, hotter, scaled-down version of typical starbursts found in other galaxies.

scholarly journals Ground-Based Optical Deep Pencil Beam Surveys

2003 ◽  
Vol 211 ◽  
pp. 203-210 ◽  
Author(s):  
P. C. Boeshaar ◽  
V. Margoniner
Keyword(s):  
Spatial Distribution ◽  
Large Volume ◽  
Brown Dwarfs ◽  
Scale Height ◽  
Galactic Latitude ◽  
Pencil Beam ◽  
Hydrogen Burning ◽  
High Galactic Latitude ◽  
Low Probability ◽  
Initial Results

The initial results of the Deep Lens Survey (http://dls.bell-labs.com) to identify possible brown dwarfs and extremely metal poor red halo subdwarfs near the hydrogen burning limit are presented. Individual deep CCD high galactic latitude survey fields appear to offer a low probability of discovering field BD's, but taken collectively offer an opportunity to begin addressing questions regarding the scale height and distribution of these objects. In all likelihood, the very depth of such surveys will greatly increase our knowledge of the coolest extreme halo objects, which currently are known in far fewer numbers than T dwarfs. Ultimately, the large volume surveyed by the Large Synoptic Survey Telescope will identify vast numbers of such objects, providing a more complete picture of their spatial distribution.

On the Spatial Distribution of Hard X‐Rays from Solar Flare Loops

1999 ◽  
Vol 527 (2) ◽  
pp. 945-957 ◽  
Author(s):  
Vahe Petrosian ◽  
Timothy Q. Donaghy
Keyword(s):  
Spatial Distribution ◽  
Solar Flare ◽  
X Rays ◽  
Flare Loops

The 6.4 keV Fe Line and the SiO Emission in the GC

2001 ◽  
Vol 205 ◽  
pp. 36-37
Author(s):  
J. Martín-Pintado ◽  
P. de Vicente ◽  
N. Rodríguez-Fernández ◽  
A. Fuente ◽  
P. Planesas
Keyword(s):  
Spatial Distribution ◽  
Gas Phase ◽  
Molecular Clouds ◽  
Galactic Center ◽  
X Rays ◽  
Refractory Elements

We present a map of the Galactic center in the J=l-0 line of SiO covering the region mapped with the ASCA satellite in the 6.4 keV Fe line. We find a correlation between the spatial distribution of the Fe 6.4 keV line and the SiO emission. The SiO abundance increases by more than a factor of 20 in the regions with strong Fe 6.4 keV line. This indicates that the Fe 6.4 keV line mainly arises from molecular clouds with large gas phase abundance of refractory elements. We discuss the implications of the correlation on the origin of the hard X-rays, and the heating and the chemistry of the molecular clouds in the GC.

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