The dipole anisotropy of the 2 Micron All-Sky Redshift Survey     

P. Erdo&#;du  J. P. Huchra  O. Lahav  M. Colless  R. M. Cutri  E. Falco  T. George  T. Jarrett  D. H. Jones  C. S. Kochanek  L. Macri  J. Mader  N. Martimbeau  M. Pahre  Q. Parker  A. Rassat  W. Saunders 《Monthly notices of the Royal Astronomical Society》2006,368(4):1515-1526

We estimate the acceleration on the Local Group (LG) from the 2 Micron All-Sky Redshift Survey (2MRS). The sample used includes about 23 200 galaxies with extinction-corrected magnitudes brighter than   K _s= 11.25  and it allows us to calculate the flux-weighted dipole. The near-infrared flux-weighted dipoles are very robust because they closely approximate a mass-weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. This is combined with the redshift information to determine the change in dipole with distance. The misalignment angle between the LG and the cosmic microwave background (CMB) dipole drops to  12°± 7°  at around  50  h ⁻¹ Mpc  , but then increases at larger distances, reaching  21°± 8°  at around  130  h ⁻¹ Mpc  . Exclusion of the galaxies Maffei 1, Maffei 2, Dwingeloo 1, IC342 and M87 brings the resultant flux dipole to  14°± 7°  away from the CMB velocity dipole. In both cases, the dipole seemingly converges by  60  h ⁻¹ Mpc  . Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters  Ω^0.6_m/ b _L= 0.40 ± 0.09  .  相似文献   

From the editors     

Xiaozhai Qi George C. Lee 《地震工程与工程振动(英文版)》2005,4(2):I0002-I0002

As the Journal of Earthquake Engineering and Engineering Vibration enters its fourth year of publication, we believe the first six issues are on the right track toward promoting scientific exchange between China, the United States and the international community. Our contributors have hailed from many countries throughout the world including Canada, China, Greece, Italy, India, Japan, Korea, New Zealand, Turkey and the United States.  相似文献   

Starspots: The zebra effect     

Bjørn R. Pettersen  Suzanne L. Hawley  George H. Fisher 《Solar physics》1992,142(1):197-204

Recent observations of brightness variations on the Sun during the solar cycle have motivated us to re-examine the widely held view that cool, dark starspots, covering a significant fraction of the star, are the centers of magnetic activity on BY Dra stars. We propose that the magnetic regions are better described by a bright facular network, and that the dark areas which give rise to photometric rotational modulation are actually regions where the underlying quiet photosphere is seen. This interpretation is consistent with recent observations of late-type stars that show that bright areas covering much of the star have magnetic fields with strengths of several thousand gauss. It resolves several problems with the current model, including the size, location, and stability of the starspots required to match photometric and Doppler-imaging observations. It also has interesting observational implications for the correlation of photometric rotational modulation and long term brightness variations with other surface activity, and for the positions of magnetically active stars in the H-R diagram.Hubble Fellow.  相似文献   

Halo ejection in distant radio galaxies: jet feedback in massive galaxy formation     

Michael A. Dopita  Michiel Reuland  Wil van Breugel  Wim de Vries  S. A. Stanford  Huub Röttgering  George Miley  Bram Venemans  Hy Spinrad  Steve Dawson  Arjun Dey  Mark Lacy  Daniel Stern  Andrew Bunker 《Astrophysics and Space Science》2007,311(1-3):305-309

We present results from a Keck optical and near IR spectroscopic study of the giant emission line halos of the z>3 High Redshift Radio Galaxies (HiZRGs) 4C 41.17, 4C 60.07 and B2 0902+34. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s⁻¹ and velocity shears consistent with rotation. The inner regions contain shocked, clumpy cocoons of gas closely associated with the radio lobes with disturbed kinematics and expansion velocities and/or velocity dispersions >1000 km s⁻¹. We also find evidence for the ejection of chemically enriched material in 4C 41.17 up to a distance of ∼60 kpc along the radio-axis. We infer that these HiZRGs are undergoing a final jet-induced phase of star formation with the ejection of most of their interstellar medium before evolving to become “red and dead” Elliptical galaxies.  相似文献   

PHYSICAL PROPERTIES OF METEORITES AND INTERPLANETARY DUST PARTICLES: CLUES TO THE PROPERTIES OF THE METEORS AND THEIR PARENT BODIES     

George J. Flynn 《Earth, Moon, and Planets》2004,95(1-4):361-374

Meteorites, generally 1 cm or larger in size that are believed to sample asteroids, and interplanetary dust particles (IDPs), generally 5–50 μm in size that are believed to sample both asteroids and comets, span the size range of the meteors. Thus, the physical properties of the meteorites and the IDPs are likely to constrain the properties of the meteors and their parent bodies. Measurements of the density, porosity, longitudinal and transverse speeds of sound, elastic modulus, and bulk modulus, as well as imaging of the internal structure by Computed Microtomography indicate that unweathered samples of chondritic meteorites are more porous and have lower sound velocities than compact terrestrial rocks. In general, the IDPs are even more porous than the chondritic meteorites. The impact energy per unit target mass required to produce a barely catastrophic disruption (Q ^* _D) for anhydrous ordinary chondrite meteorites is twice that for terrestrial basalt or glass, indicating that collisional disruption of anhydrous meteorites requires more energy than for a compact basalt. These results indicate that most stone meteors are likely to be weak, porous objects, and that the parent bodies of the anhydrous stone meteorites are likely to be more difficult to disrupt than compact terrestrial basalt.  相似文献   

Overview of the Inner Front and Southeast Bering Sea Carrying Capacity Programs     

Phyllis J. Stabeno  George L. Hunt  Jr.   《Deep Sea Research Part II: Topical Studies in Oceanography》2002,49(26)

  相似文献   

The 2dF Galaxy Redshift Survey: galaxy clustering per spectral type     

Darren S. Madgwick  Ed Hawkins  Ofer Lahav  Steve Maddox  Peder Norberg  John A. Peacock  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ian Lewis  Stuart Lumsden  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2003,344(3):847-856

  相似文献   

The 2dF Galaxy Redshift Survey: the population of nearby radio galaxies at the 1-mJy level     

Manuela Magliocchetti  Steve J. Maddox  Carole A. Jackson  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto de Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Ofer Lahav  Ian Lewis  Stuart Lumsden  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,333(1):100-120

  相似文献   

The Galileo star scanner observations at Amalthea     

Paul D Fieseler  Olen W Adams  Nancy Vandermey  E.E Theilig  Kathryn A Schimmels  George D Lewis  Shadan M Ardalan  Claudia J Alexander 《Icarus》2004,169(2):390-401

In November of 2002, the Galileo spacecraft passed within 250 km of Jupiter's moon Amalthea. An onboard telescope, the star scanner, observed a series of bright flashes near the moon. It is believed that these flashes represent sunlight reflected from 7 to 9 small moonlets located within about 3000 km of Amalthea. From star scanner geometry considerations and other arguments, we can constrain the diameter of the observed bodies to be between 0.5 m to several tens of kilometers. In September of 2003, while crossing Amalthea's orbit just prior to Galileo's destruction in the jovian atmosphere, a single additional body seems to have been observed. It is suspected that these bodies are part of a discrete rocky ring embedded within Jupiter's Gossamer ring system.  相似文献   

The 2dF Galaxy Redshift Survey: the clustering of galaxy groups     

Nelson D. Padilla  Carlton M. Baugh  Vincent R. Eke  Peder Norberg  Shaun Cole  Carlos S. Frenk  Darren J. Croton  Ivan K. Baldry  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,352(1):211-225

  相似文献