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The relative age of galaxies at different redshifts can be used to infer the Hubble parameter and put constraints on cosmological models. We select 23,883 quiescent luminous red galaxies (LRGs) from the SDSS DR7, dividing them into four sub-samples according to their velocity dispersions. Each sub-sample was further divided into 12 redshift bins. The spectra of the LRGs in each redshift and velocity bin were co-added. Adopting the GalexEV/SteLib model, we estimate the mean ages of the LRGs from these combined spectra by the full-spectrum fitting method and find it is consistent with the well known “downsizing” formation of galaxies. Based on the age–redshift relation, we further estimate the Hubble parameter.
We test observational consequences of primordial Kerr superspinars indicated by string theories. We demonstrate that Kerr superspinars can serve as ultra-high energy accelerators and explore specific optical phenomena related to accretion discs orbiting them.
SMA observations of molecular gas and dust in nearby galactic centers are presented to showcase remarkable ISM properties including warm to very hot gas, molecular clouds producing massive star clusters, and mechanical feedback through bubbles and outflows.
The family of unidentified infrared emission features, consisting of discrete and plateau features in the mid-infrared, are now observed in distant galaxies. A significant fraction of the total energy output of some infrared galaxies is emitted in these features. Comparisons of these features with those observed in the circumstellar and interstellar media suggest that these organic species are synthesized and ejected by evolved stars. Models of possible chemical structures of the carrier of these features are discussed.
Zhongguo guidai tianxiang jilu zongji pressed in 1988 containes ancient Chinese astronomical records including that of meteor, meteorite fall and comet until 1911 from the Standard Histories and local gazetteers existed in China. On the other hand, many local gazetteers lost in China at present have been collected in university and public libraries in Japan. Especially the library of Chinese section in the Research Institute for Humanistic Studies in Kyoto University and the Oriental Library in Tokyo have big collection. This presentation will give a few dozens supplemential ancient records with that big book from local gazetteers in above mentioned libraries.
The magnetorotational instability (MRI) is widely believed to be the source of turbulence in accretion discs. This turbulence is responsible for the anomalous angular momentum transport in accretion discs. The turbulence will affect other aspects of the dynamics of the disc as well, and we will concentrate on two such issues: a) what kind of oscillations can be excited by the turbulence itself, and b) how the turbulence is interacting with modes that have been excited by some other agent. This is of interest in understanding the quasi-periodic oscillations (QPOs) that have been observed in the X-ray light curves of accreting neutron star and black hole binaries. We carry out local three dimensional (3D) magnetohydrodynamic simulations of a keplerian differentially rotating accretion disc, using a shearing box configuration taking in account the effects of the vertical stratification.
We investigated the connection between AGN and star formation (SF) activities of various kinds of AGNs and their host galaxies. In order to probe SF activity, we measured the 3.3 μm PAH emission luminosity utilizing the slitless spectroscopic capability of AKARI space telescope. We present the results from two missions, ASCSG and LQSONG.
We model the evolution of the magnetic fields of neutron stars as consisting of a long term power-law decay modulated by short term small amplitude oscillations. Our model predictions on the timing noise of neutron stars agree well with the observed statistical properties and correlations of normal radio pulsars. For individual pulsars our model can effectively reduce their timing residuals, thus offering the potential of more sensitive detections of gravitational waves with pulsar timing arrays. Finally our model can also re-produce their observed correlation and oscillations of second derivative of frenquency, as well as the “slow glitch” phenomenon.
We investigated comets active at large heliocentric distances using observations obtained at the 6-m BTA telescope (SAO RAS, Russia). Long-slit and photometric modes of the focal reducer SCORPIO were used. Two of the comets, 29P/Schwassmann-Wachmann 1 (SW1) and C/2002 VQ94 (LINEAR) were observed to be emission rich. Detection of CO+ and N2 + emissions in the comae of these comets is evidence that they were formed in the outer regions of the Solar System or in a pre-solar interstellar cloud in a low temperature environment with T ~ 25K. The ratio of N2+/CO+ is equal to 0.011 and 0.027 for SW1 and LINEAR, respectively. Comet LINEAR is the most distant object in the Solar System (7.332 AU) for which CO+ and N2+ are measured. The photometric maximum of the isolated CO+ coma in comet LINEAR is shifted by 1.4 arcsec (7.44 × 103 km) relative to the photometric maximum of the dust coma. This shift deviates from the sunward direction by 63 degrees.
We present results of convective turbulent dynamo simulations including a coronal layer in a spherical wedge. We find an equatorward migration of the radial and azimuthal fields similar to the behavior of sunspots during the solar cycle. The migration of the field coexist with a spoke-like differential rotation and anti-solar (clockwise) meridional circulation. Even though the migration extends over the whole convection zone, the mechanism causing this is not yet fully understood.
In 2012, at the time of the Beijing GA, two decades had passed since the publication of the Spaceguard Report. Time has not passed in vain for the subject of NEO-related hazards, and we are currently in a totally different situation than in the early nineties. The amount of work done, and the level of awareness of the underlying problems, have both risen to such a level that a re-assessment by the astronomical community of its rôle and involvement was in order, and the GA Special Session 7 “The impact hazard: current activities and future plans” was aimed exactly at that.
Local early-type galaxies (ETGs), despite typically being associated to old stellar populations and passive evolution, have been in some cases observed to present peculiarities in their stellar structure, like disks and shells (e.g., Kormendy et al.1997, Rix, Carollo & Freeman 1999). Moreover, it has been observed that ETGs with such tidal features may present UV emission (Rampazzo et al.2007, Salim & Rich 2010). These properties make them relevant constraints to galaxy formation models. We are analysing the structure of nearby ETGs observed in the Spitzer Survey of Stellar Structure in Galaxies (S4G; Sheth et al.2010), which comprises the largest mid-IR survey of galaxies in the local Universe. We perform a 2D GALFIT decomposition of the 3.6μm images of 146 ETGs and examine their residual images. We identify tidal features in 17% of these, suggesting that a non-negligible ETGs fraction may have experienced (after the formation of the bulk of their stellar budget) merger events that have left signatures (Canalizo et al.2007). For 6 of these peculiar ETGs, we also applied GALFIT decomposition to public GALEX/UV and SDSS/optical images. With measurements in multiple bands, we applied SED fitting techniques to estimate star formation rates (SFR) and stellar masses for the galaxies and their tidal features. We find that these 6 peculiar ETGs present masses in agreement with the population of non-peculiar ETGs. However, SFRs are higher than what has been measured for the average ETG population (Shapiro et al.2010, SDSS MPA-JHU catalog). Based on the Kaviraj (2010) relation, we find that for these peculiar ETGs the estimated age of the most recent star formation event is less than 3Gyrs. Despite this indication of recent star formation, we have not found evidence of prominent UV emission in the tidal features (Marino et al.2010). We are currently extending our work to the full sample of peculiar ETGs identified in our sample.
We cross-matched Wide-field Infrared Survey Explorer sources with the Sloan Digital Sky Survey galaxy spectroscopic catalog within 6 arcsec to produce 182798 galaxies with 22 μm signal to noise > 3. The different redshift bins of the sample show that the rest-frame 22μm luminosities increase with redshift, for rest-frame 22μm luminosities in the range of 106 − 1012 L⊙. The infrared sample is located in the blue sequence. The Seyfert fraction increases with redshift more obviously in the IR sample than in an optical control sample. The Seyfert fraction increases significantly with increasing rest-frame 22 μm luminosity below 1011 L⊙.
Planet migration plays a crucial role in shaping planetary systems, and has therefore received a lot of attention in recent years in an effort to compare the statistical properties of observed exoplanets with the predictions of planet formation and migration theories. By modifying the propagation properties of the waves induced by the planet in the disk, the presence of a strong magnetic field can dramatically influence planet migration, in some cases reversing its direction. The more realistic case of a weaker magnetic field is less clear, although turbulent MHD simulations by Baruteau et al. (2011) suggest an effect on the corotation torque. Here, we present a study of the corotation torque in 2D laminar disks containing a toroidal magnetic field. We performed MHD simulations of the interaction between the magnetic field and the horseshoe motion of the gas, and found that this results in an additional corotation torque. This additional torque can be strong enough to reverse migration even for a field which pressure is only one percent of the thermal pressure. We speculate that this could lead to long range outward migration in the outer part of protoplanetary disks and may explain the observations by direct imaging of planets at several tens of AU from their star like the 4 planets system HR 8799.
The Spitzer Legacy Program “Surveying the Agents of Galaxy Evolution in the Tidally-Stripped, Low-Metallicity Small Magellanic Cloud” (SAGE-SMC; Gordon et al. 2011) allows a global study of star formation in the SMC at high enough resolution to resolve individual cores and protostars at a range of mid-IR wavelengths. Using the SAGE-SMC IRAC (3.6 - 8.0 μm) and MIPS (24 and 70 μm) catalogs and images combined with the near-IR and optical data, we identified a population of ∼1100 intermediate- to high-mass Young Stellar Objects (YSOs) in the SMC (3 × more than previously known). We investigate the properties of the YSOs and how they relate to the galaxy's structure and gas and dust distribution.
The formation of terrestrial and gas giant planets has likely imprinted signatures on the chemical composition of their parent stars, as shown for example by the higher occurrence of giant planets for higher stellar metallicities. There are two new signatures that have been recently proposed by Meléndez et al. (2009, 2012) and Ramírez et al. (2009, 2010) for the formation of rocky planets, and by Ramírez et al. (2011) for gas giant planets. We review here our on-going work on the planet-star connection using solar twins, for which chemical abundances are being obtained at unprecedented precision (0.01 dex).
Project Dwarf is a new observing campaign focused on the detection of substellar companions to low-mass (composed of late-type, subdwarf (sd) or/and white dwarf (WD) components) detached eclipsing binaries using minima timing. The crucial condition for the object selection for this campaign is possibility to determine times of the minima with high precision. This is naturally fullfilled for eclipsing binaries with deep and narrow minima or systems hosting a WD component showing fast ingress or egress.
The observing project includes three groups of close eclipsing binaries indicating presence of substellar circum-binary components:
(i) systems with K or/and M dwarf components
(ii) systems with hot subdwarf (sd) and M dwarf components
(iii) systems with white dwarf (WD) component(s).
The sample of the eclipsing systems have orbital periods in range of 0.1 to almost 3 days and their brightness fits possibilities of small telescopes equipped with a low-end CCD camera and at least VRI filter set. Such kind of telescopes allow us to develop observing network including also amateur astronomers.
During the past 20 years, numerous stellar streams have been discovered in both the Milky Way and the Local Group. These streams have been tidally torn from orbiting systems, which suggests that most should roughly trace the orbit of their progenitors around the Galaxy. As a consequence, they play a fundamental role in understanding the formation and evolution of our Galaxy. This project is based on the possibility of applying a technique developed by Binney to various tidal streams and overdensities in the Galaxy. The aim is to develop an efficient method to constrain the Galactic gravitational potential, to determine its mass distribution, and to test distance measurements. Here we apply the technique to the Grillmair & Dionatos GD-1 cold stellar stream. In the unrealistic case of noise-free data, the results show that the technique provides excellent discrimination against incorrect potentials and that it is possible to predict the heliocentric distance very accurately. This changes dramatically when errors are taken into account, which wash out most of the results. Nevertheless, it is still possible to rule out spherical potentials and set constraints on the distance of a given stream.
Flares are observed on a wide variety of stellar types, ranging from closely orbiting binary systems consisting of an evolved member (RS CVn's) and young, nearby super-active M dwarfs (dMe's). The timescales and energies of flares span many orders of magnitude and typically far exceed the scales of even the largest solar flares observed. In particular, the active M dwarfs produce an energetic signature in the near-UV and optical continuum, which is often referred to as the white-light continuum. White-light emission has been studied in Johnson UBVR filters during a few large-amplitude flares, and the best emission mechanism that fits the broadband color distribution is a T~104 K blackbody (Hawley & Fisher 1992). Time-resolved blue spectra have revealed a consistent picture, with little or no Balmer jump and a smoothly rising continuum toward the near-UV (Hawley & Pettersen 1991). However, the most recent self-consistent radiative-hydrodynamic (RHD) models, which use a solar-type flare heating function from accelerated, nonthermal electrons, do not reproduce this emission spectrum. Instead, these models predict that the white-light is dominated by Balmer continuum emission from Hydrogen recombination in the chromosphere (Allred et al. 2006). Moreover, Allred et al. (2006) showed that the Johnson colors of the model prediction exhibit a broadband distribution similar to a blackbody with T~9000 K.
Parkes pulse arrival-time data for 165 radio pulsars spanning from 1990 to 2011 have been searched for period glitches. Forty-six events out of the detected 107 glitches were found to be new contributions to the entire glitch population which currently contains approximately 400 events.