Shude Mao - and IRIS team

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Shude Mao
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and IRIS team
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Astrophysics of Galaxies (35)
 
Cosmology and Nongalactic Astrophysics (12)
 
Earth and Planetary Astrophysics (7)
 
High Energy Astrophysical Phenomena (5)
 
Instrumentation and Methods for Astrophysics (3)
 
Solar and Stellar Astrophysics (1)

Publications Authored By Shude Mao

2017May
Affiliations: 1Tsinghua Univ, 2UCSC/UCO, 3SYNU, 4UCSC/UCO, 5NASA GSFC, 6UCSC/UCO, 7STScI, 8Tsinghua Univ, 9Orange Coast College, 10Shanghai Normal Univ, 11STScI, 12Colby College, 13CfA

This paper uses radial colour profiles to infer the distributions of dust, gas and star formation in z=0.4-1.4 star-forming main sequence galaxies. Read More

With a sample of 48,161 K giant stars selected from the LAMOST DR 2 catalogue, we construct torus models in a large volume extending, for the first time, from the solar vicinity to a Galactocentric distance of $\sim 20$ kpc, reaching the outskirts of the Galactic disc. We show that the kinematics of the K giant stars match conventional models, e.g. Read More

We report the discovery of a microlensing planet --- MOA-2016-BLG-227Lb --- with a large planet/host mass ratio of $q \simeq 9 \times 10^{-3}$. This event was located near the $K2$ Campaign 9 field that was observed by a large number of telescopes. As a result, the event was in the microlensing survey area of a number of these telescopes, and this enabled good coverage of the planetary light curve signal. Read More

We perform Jeans anisotropic modeling (JAM) on elliptical and spiral galaxies from the MaNGA DR13 sample. By comparing the stellar mass-to-light ratios estimated from stellar population synthesis (SPS) and from JAM, we find a similar systematic variation of the initial mass function (IMF) as in the earlier $\rm ATLAS^{3D}$ results. Early type galaxies (elliptical and lenticular) with lower velocity dispersions within one effective radius are consistent with a Chabrier-like IMF while galaxies with higher velocity dispersions are consistent with a more bottom heavy IMF such as the Salpeter IMF. Read More

2017Feb
Authors: Michael R. Blanton, Matthew A. Bershady, Bela Abolfathi, Franco D. Albareti, Carlos Allende Prieto, Andres Almeida, Javier Alonso-García, Friedrich Anders, Scott F. Anderson, Brett Andrews, Erik Aquino-Ortíz, Alfonso Aragón-Salamanca, Maria Argudo-Fernández, Eric Armengaud, Eric Aubourg, Vladimir Avila-Reese, Carles Badenes, Stephen Bailey, Kathleen A. Barger, Jorge Barrera-Ballesteros, Curtis Bartosz, Dominic Bates, Falk Baumgarten, Julian Bautista, Rachael Beaton, Timothy C. Beers, Francesco Belfiore, Chad F. Bender, Andreas A. Berlind, Mariangela Bernardi, Florian Beutler, Jonathan C. Bird, Dmitry Bizyaev, Guillermo A. Blanc, Michael Blomqvist, Adam S. Bolton, Médéric Boquien, Jura Borissova, Remco van den Bosch, Jo Bovy, William N. Brandt, Jonathan Brinkmann, Joel R. Brownstein, Kevin Bundy, Adam J. Burgasser, Etienne Burtin, Nicolás G. Busca, Michele Cappellari, Maria Leticia Delgado Carigi, Joleen K. Carlberg, Aurelio Carnero Rosell, Ricardo Carrera, Brian Cherinka, Edmond Cheung, Yilen Gómez Maqueo Chew, Cristina Chiappini, Peter Doohyun Choi, Drew Chojnowski, Chia-Hsun Chuang, Haeun Chung, Rafael Fernando Cirolini, Nicolas Clerc, Roger E. Cohen, Johan Comparat, Luiz da Costa, Marie-Claude Cousinou, Kevin Covey, Jeffrey D. Crane, Rupert A. C. Croft, Irene Cruz-Gonzalez, Daniel Garrido Cuadra, Katia Cunha, Guillermo J. Damke, Jeremy Darling, Roger Davies, Kyle Dawson, Axel de la Macorra, Nathan De Lee, Timothée Delubac, Francesco Di Mille, Aleks Diamond-Stanic, Mariana Cano-Díaz, John Donor, Juan José Downes, Niv Drory, Hélion du Mas des Bourboux, Christopher J. Duckworth, Tom Dwelly, Jamie Dyer, Garrett Ebelke, Daniel J. Eisenstein, Eric Emsellem, Mike Eracleous, Stephanie Escoffier, Michael L. Evans, Xiaohui Fan, Emma Fernández-Alvar, J. G. Fernandez-Trincado, Diane K. Feuillet, Alexis Finoguenov, Scott W. Fleming, Andreu Font-Ribera, Alexander Fredrickson, Gordon Freischlad, Peter M. Frinchaboy, Lluís Galbany, R. Garcia-Dias, D. A. García-Hernández, Patrick Gaulme, Doug Geisler, Joseph D. Gelfand, Héctor Gil-Marín, Bruce A. Gillespie, Daniel Goddard, Violeta Gonzalez-Perez, Kathleen Grabowski, Paul J. Green, Catherine J. Grier, James E. Gunn, Hong Guo, Julien Guy, Alex Hagen, ChangHoon Hahn, Matthew Hall, Paul Harding, Sten Hasselquist, Suzanne L. Hawley, Fred Hearty, Jonay I. Gonzalez Hernández, Shirley Ho, David W. Hogg, Kelly Holley-Bockelmann, Jon A. Holtzman, Parker H. Holzer, Joseph Huehnerhoff, Timothy A. Hutchinson, Ho Seong Hwang, Héctor J. Ibarra-Medel, Gabriele da Silva Ilha, Inese I. Ivans, KeShawn Ivory, Kelly Jackson, Trey W. Jensen, Jennifer A. Johnson, Amy Jones, Henrik Jönsson, Eric Jullo, Vikrant Kamble, Karen Kinemuchi, David Kirkby, Francisco-Shu Kitaura, Mark Klaene, Gillian R. Knapp, Jean-Paul Kneib, Juna A. Kollmeier, Ivan Lacerna, Richard R. Lane, Dustin Lang, David R. Law, Daniel Lazarz, Jean-Marc Le Goff, Fu-Heng Liang, Cheng Li, Hongyu LI, Marcos Lima, Lihwai Lin, Yen-Ting Lin, Sara Bertran de Lis, Chao Liu, Miguel Angel C. de Icaza Lizaola, Dan Long, Sara Lucatello, Britt Lundgren, Nicholas K. MacDonald, Alice Deconto Machado, Chelsea L. MacLeod, Suvrath Mahadevan, Marcio Antonio Geimba Maia, Roberto Maiolino, Steven R. Majewski, Elena Malanushenko, Viktor Malanushenko, Arturo Manchado, Shude Mao, Claudia Maraston, Rui Marques-Chaves, Karen L. Masters, Cameron K. McBride, Richard M. McDermid, Brianne McGrath, Ian D. McGreer, Nicolás Medina Peña, Matthew Melendez, Andrea Merloni, Michael R. Merrifield, Szabolcs Meszaros, Andres Meza, Ivan Minchev, Dante Minniti, Takamitsu Miyaji, Surhud More, John Mulchaey, Francisco Müller-Sánchez, Demitri Muna, Ricardo R. Munoz, Adam D. Myers, Preethi Nair, Kirpal Nandra, Janaina Correa do Nascimento, Alenka Negrete, Melissa Ness, Jeffrey A. Newman, Robert C. Nichol, David L. Nidever, Christian Nitschelm, Pierros Ntelis, Julia E. O'Connell, Ryan J. Oelkers, Audrey Oravetz, Daniel Oravetz, Zach Pace, Nelson Padilla, Nathalie Palanque-Delabrouille, Pedro Alonso Palicio, Kaike Pan, Taniya Parikh, Isabelle Pâris, Changbom Park, Alim Y. Patten, Sebastien Peirani, Marcos Pellejero-Ibanez, Samantha Penny, Will J. Percival, Ismael Perez-Fournon, Patrick Petitjean, Matthew M. Pieri, Marc Pinsonneault, Alice Pisani, Radosław Poleski, Francisco Prada, Abhishek Prakash, Anna Bárbara de Andrade Queiroz, M. Jordan Raddick, Anand Raichoor, Sandro Barboza Rembold, Hannah Richstein, Rogemar A. Riffel, Rogério Riffel, Hans-Walter Rix, Annie C. Robin, Constance M. Rockosi, Sergio Rodríguez-Torres, A. Roman-Lopes, Carlos Román-Zúñiga, Margarita Rosado, Ashley J. Ross, Graziano Rossi, John Ruan, Rossana Ruggeri, Eli S. Rykoff, Salvador Salazar-Albornoz, Mara Salvato, Ariel G. Sánchez, David Sánchez Aguado, José R. Sánchez-Gallego, Felipe A. Santana, Basílio Xavier Santiago, Conor Sayres, Ricardo P. Schiavon, Jaderson da Silva Schimoia, Edward F. Schlafly, David J. Schlegel, Donald P. Schneider, Mathias Schultheis, William J. Schuster, Axel Schwope, Hee-Jong Seo, Zhengyi Shao, Shiyin Shen, Matthew Shetrone, Michael Shull, Joshua D. Simon, Danielle Skinner, M. F. Skrutskie, Anže Slosar, Verne V. Smith, Jennifer S. Sobeck, Flavia Sobreira, Garrett Somers, Diogo Souto, David V. Stark, Keivan Stassun, Fritz Stauffer, Matthias Steinmetz, Thaisa Storchi-Bergmann, Alina Streblyanska, Guy S. Stringfellow, Genaro Suárez, Jing Sun, Nao Suzuki, Laszlo Szigeti, Manuchehr Taghizadeh-Popp, Baitian Tang, Charling Tao, Jamie Tayar, Mita Tembe, Johanna Teske, Aniruddha R. Thakar, Daniel Thomas, Benjamin A. Thompson, Jeremy L. Tinker, Patricia Tissera, Rita Tojeiro, Hector Hernandez Toledo, Sylvain de la Torre, Christy Tremonti, Nicholas W. Troup, Octavio Valenzuela, Inma Martinez Valpuesta, Jaime Vargas-González, Mariana Vargas-Magaña, Jose Alberto Vazquez, Sandro Villanova, M. Vivek, Nicole Vogt, David Wake, Rene Walterbos, Yuting Wang, Benjamin Alan Weaver, Anne-Marie Weijmans, David H. Weinberg, Kyle B. Westfall, David G. Whelan, Vivienne Wild, John Wilson, W. M. Wood-Vasey, Dominika Wylezalek, Ting Xiao, Renbin Yan, Meng Yang, Jason E. Ybarra, Christophe Yèche, Nadia Zakamska, Olga Zamora, Pauline Zarrouk, Gail Zasowski, Kai Zhang, Gong-Bo Zhao, Zheng Zheng, Zhi-Min Zhou, Guangtun B. Zhu, Manuela Zoccali, Hu Zou

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratio in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially-resolved spectroscopy for thousands of nearby galaxies (median redshift of z = 0. Read More

The Beijing-Arizona Sky Survey (BASS) is a wide-field two-band photometric survey of the Northern Galactic Cap using the 90Prime imager on the 2.3 m Bok telescope at Kitt Peak. It is a four-year collaboration between the National Astronomical Observatory of China and Steward Observatory, the University of Arizona, serving as one of the three imaging surveys to provide photometric input catalogs for target selection of the Dark Energy Spectroscopic Instrument (DESI) project. Read More

The Beijing-Arizona Sky Survey (BASS) is a new wide-field legacy imaging survey in the northern Galactic cap using the 2.3m Bok telescope. The survey will cover about 5400 deg$^2$ in the $g$ and $r$ bands, and the expected 5$\sigma$ depths (corrected for the Galactic extinction) in the two bands are 24. Read More

We present a study on the stellar age and metallicity distributions for 1105 galaxies using the STARLIGHT software on MaNGA integral field spectra. We derive age and metallicity gradients by fitting straight lines to the radial profiles, and explore their correlations with total stellar mass M*, NUV-r colour and environments, as identified by both the large scale structure (LSS) type and the local density. We find that the mean age and metallicity gradients are close to zero but slightly negative, which is consistent with the inside-out formation scenario. Read More

The dynamics and evolution of any galactic structure are strongly influenced by the properties of the orbits that constitute it. In this paper, we compare two orbit classification schemes, one by Laskar (NAFF) , and the other by Carpintero and Aguilar (CA), by applying both of them to orbits obtained by following individual particles in a numerical simulation of a barred galaxy. We find that, at least for our case and some provisos, the main frequencies calculated by the two methods are in good agreement: for $80\%$ of the orbits the difference between the results of the two methods is less than $5\%$ for all three main frequencies. Read More

We present \textsl{Hubble Space Telescope} (\textsl{HST}) F606W-band imaging observations of 21 galaxy-Ly$\alpha$ emitter lens candidates in the Baryon Oscillation Spectroscopic Survey (BOSS) Emission-Line Lens Survey (BELLS) for GALaxy-Ly$\alpha$ EmitteR sYstems (BELLS GALLERY) survey. 17 systems are confirmed to be definite lenses with unambiguous evidence of multiple imaging. The lenses are primarily massive early-type galaxies (ETGs) at redshifts of approximately $0. Read More

The MaNGA Survey (Mapping Nearby Galaxies at Apache Point Observatory) is one of three core programs in the Sloan Digital Sky Survey IV. It is obtaining integral field spectroscopy (IFS) for 10K nearby galaxies at a spectral resolution of R~2000 from 3,622-10,354A. The design of the survey is driven by a set of science requirements on the precision of estimates of the following properties: star formation rate surface density, gas metallicity, stellar population age, metallicity, and abundance ratio, and their gradients; stellar and gas kinematics; and enclosed gravitational mass as a function of radius. Read More

We calculate the microlensing event rate and typical time-scales for the free-floating planet (FFP) population that is predicted by the core accretion theory of planet formation. The event rate is found to be ~$1.8\times 10^{-3}$ of that for the stellar population. Read More

With the aim of exploring the fast evolutionary path from the blue cloud of star-forming galaxies to the red sequence of quiescent galaxies in the local universe, we select a local advanced merging infrared luminous and ultraluminous galaxy (adv-merger (U)LIRGs) sample and perform careful dust extinction corrections to investigate their positions in the SFR-$M_{\ast}$, u-r and NUV-r color-mass diagrams. The sample consists of 89 (U)LIRGs at the late merger stage, obtained from cross-correlating the IRAS Point Source Catalog Redshift Survey and 1 Jy ULIRGs samples with the Sloan Digital Sky Survey DR7 database. Our results show that $74\%\pm 5\%$ of adv-merger (U)LIRGs are localized above the $1\, \sigma$ line of the local star-forming galaxy main sequence. Read More

The rest-frame UV-optical (i.e., NUV-B) color index is sensitive to the low-level recent star formation and dust extinction, but it is insensitive to the metallicity. Read More

We introduce the Baryon Oscillation Spectroscopic Survey (BOSS) Emission-Line Lens Survey (BELLS) for GALaxy-Ly$\alpha$ EmitteR sYstems (BELLS GALLERY) Survey, which is a Hubble Space Telescope program to image a sample of galaxy-scale strong gravitational lens candidate systems with high-redshift Ly$\alpha$ emitters (LAEs) as the background sources. The goal of the BELLS GALLERY Survey is to illuminate dark substructures in galaxy-scale halos by exploiting the small-scale clumpiness of rest-frame far-UV emission in lensed LAEs, and to thereby constrain the slope and normalization of the substructure-mass function. In this paper, we describe in detail the spectroscopic strong-lens selection technique, which is based on methods adopted in the previous Sloan Lens ACS (SLACS) Survey, BELLS, and SLACS for the Masses Survey. Read More

We assess the effectiveness of the Jeans-Anisotropic-MGE (JAM) technique with a state-of-the-art cosmological hydrodynamic simulation, the Illustris project. We perform JAM modelling on 1413 simulated galaxies with stellar mass M^* > 10^{10}M_{sun}, and construct an axisymmetric dynamical model for each galaxy. Combined with a Markov Chain Monte Carlo (MCMC) simulation, we recover the projected root-mean-square velocity (V_rms) field of the stellar component, and investigate constraints on the stellar mass-to-light ratio, M^*/L, and the fraction of dark matter f_{DM} within 2. Read More

Measurement of the local dark matter density plays an important role in both Galactic dynamics and dark matter direct detection experiments. However, the estimated values from previous works are far from agreeing with each other. In this work, we provide a well-defined observed sample with 1427 G \& K type main-sequence stars from the LAMOST spectroscopic survey, taking into account selection effects, volume completeness, and the stellar populations. Read More

Time delays in gravitational lenses can be used to determine the Hubble constant and the lens potential. In future surveys, many gravitational lenses can be discovered, and their time delays and image positions can in principle be measured. Using an elliptical power-law potential, we show that combinations of image positions and time delays for quadruple lenses yield simple analytical expressions that are connected with observable quantities. Read More

We present an analysis of the diffuse soft X-ray emission from the nuclear region of M51 combining both XMM-Newton RGS and Chandra data. Most of the RGS spectrum of M51 can be fitted with a thermal model with a temperature of $\sim0.5$ keV except for the OVII triplet, which is forbidden-line dominated. Read More

2015May
Authors: Warren Skidmore, Ian Dell'Antonio, Misato Fukugawa, Aruna Goswami, Lei Hao, David Jewitt, Greg Laughlin, Charles Steidel, Paul Hickson, Luc Simard, Matthias Schöck, Tommaso Treu, Judith Cohen, G. C. Anupama, Mark Dickinson, Fiona Harrison, Tadayuki Kodama, Jessica R. Lu, Bruce Macintosh, Matt Malkan, Shude Mao, Norio Narita, Tomohiko Sekiguchi, Annapurni Subramaniam, Masaomi Tanaka, Feng Tian, Michael A'Hearn, Masayuki Akiyama, Babar Ali, Wako Aoki, Manjari Bagchi, Aaron Barth, Varun Bhalerao, Marusa Bradac, James Bullock, Adam J. Burgasser, Scott Chapman, Ranga-Ram Chary, Masashi Chiba, Michael Cooper, Asantha Cooray, Ian Crossfield, Thayne Currie, Mousumi Das, G. C. Dewangan, Richard de Grijs, Tuan Do, Subo Dong, Jarah Evslin, Taotao Fang, Xuan Fang, Christopher Fassnacht, Leigh Fletcher, Eric Gaidos, Roy Gal, Andrea Ghez, Mauro Giavalisco, Carol A. Grady, Thomas Greathouse, Rupjyoti Gogoi, Puragra Guhathakurta, Luis Ho, Priya Hasan, Gregory J. Herczeg, Mitsuhiko Honda, Masa Imanishi, Hanae Inami, Masanori Iye, Jason Kalirai, U. S. Kamath, Stephen Kane, Nobunari Kashikawa, Mansi Kasliwal, Vishal Kasliwal, Evan Kirby, Quinn M. Konopacky, Sebastien Lepine, Di Li, Jianyang Li, Junjun Liu, Michael C. Liu, Enrigue Lopez-Rodriguez, Jennifer Lotz, Philip Lubin, Lucas Macri, Keiichi Maeda, Franck Marchis, Christian Marois, Alan Marscher, Crystal Martin, Taro Matsuo, Claire Max, Alan McConnachie, Stacy McGough, Carl Melis, Leo Meyer, Michael Mumma, Takayuki Muto, Tohru Nagao, Joan R. Najita, Julio Navarro, Michael Pierce, Jason X. Prochaska, Masamune Oguri, Devendra K. Ojha, Yoshiko K. Okamoto, Glenn Orton, Angel Otarola, Masami Ouchi, Chris Packham, Deborah L. Padgett, Shashi Bhushan Pandey, Catherine Pilachowsky, Klaus M. Pontoppidan, Joel Primack, Shalima Puthiyaveettil, Enrico Ramirez-Ruiz, Naveen Reddy, Michael Rich, Matthew J. Richter, James Schombert, Anjan Ananda Sen, Jianrong Shi, Kartik Sheth, R. Srianand, Jonathan C. Tan, Masayuki Tanaka, Angelle Tanner, Nozomu Tominaga, David Tytler, Vivian U, Lingzhi Wang, Xiaofeng Wang, Yiping Wang, Gillian Wilson, Shelley Wright, Chao Wu, Xufeng Wu, Renxin Xu, Toru Yamada, Bin Yang, Gongbo Zhao, Hongsheng Zhao

The TMT Detailed Science Case describes the transformational science that the Thirty Meter Telescope will enable. Planned to begin science operations in 2024, TMT will open up opportunities for revolutionary discoveries in essentially every field of astronomy, astrophysics and cosmology, seeing much fainter objects much more clearly than existing telescopes. Per this capability, TMT's science agenda fills all of space and time, from nearby comets and asteroids, to exoplanets, to the most distant galaxies, and all the way back to the very first sources of light in the Universe. Read More

We explore the kinematics (both the radial velocity and the proper motion) of the vertical X-shaped feature in the Milky Way with an N-body bar/bulge model. From the solar perspective, the distance distribution of particles is double-peaked in fields passing through the X-shape. The separation and amplitude ratio between the two peaks qualitatively match the observed trends towards the Galactic bulge. Read More

We use about 15,000 F/G nearby dwarf stars selected from the LAMOST pilot survey to map the U-V velocity distribution in the solar neighbourhood. An extreme deconvolution algorithm is applied to reconstruct an empirical multi-Gaussian model. In addition to the well known substructures, e. Read More

We present an overview of a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), one of three core programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV) that began on 2014 July 1. MaNGA will investigate the internal kinematic structure and composition of gas and stars in an unprecedented sample of 10,000 nearby galaxies. We summarize essential characteristics of the instrument and survey design in the context of MaNGA's key science goals and present prototype observations to demonstrate MaNGA's scientific potential. Read More

Discrepancies between the observed and model-predicted radio flux ratios are seen in a number of quadruply-lensed quasars. The most favored interpretation of these anomalies is that CDM substructures present in lensing galaxies perturb the lens potentials and alter image magnifications and thus flux ratios. So far no consensus has emerged regarding whether or not the predicted CDM substructure abundance fully accounts for the lensing flux anomaly observations. Read More

We undertake the first study of two-planet microlensing models recovered from simulations of microlensing events generated by realistic multi-planet systems in which 292 planetary events including 16 two-planet events were detected from 6690 simulated light curves. We find that when two planets are recovered, their parameters are usually close to those of the two planets in the system most responsible for the perturbations. However, in one of the 16 examples, the apparent mass of both detected planets was more than doubled by the unmodeled influence of a third, massive planet. Read More

2014Jul
Affiliations: 1and IRIS team, 2and IRIS team, 3and IRIS team, 4and IRIS team, 5and IRIS team, 6and IRIS team, 7and IRIS team, 8and IRIS team, 9and IRIS team, 10and IRIS team, 11and IRIS team, 12and IRIS team, 13and IRIS team, 14and IRIS team, 15and IRIS team, 16and IRIS team, 17and IRIS team, 18and IRIS team, 19and IRIS team, 20and IRIS team, 21and IRIS team, 22and IRIS team, 23and IRIS team, 24and IRIS team, 25and IRIS team

IRIS (InfraRed Imaging Spectrograph) is a first light near-infrared diffraction limited imager and integral field spectrograph being designed for the future Thirty Meter Telescope (TMT). IRIS is optimized to perform astronomical studies across a significant fraction of cosmic time, from our Solar System to distant newly formed galaxies (Barton et al. [1]). Read More

We study the dynamics of the giant elliptical galaxy M87 from the central to the outermost regions with the made-to-measure (M2M) method. We use a new catalogue of 922 globular cluster line-of- sight velocities extending to a projected radius of 180 kpc (equivalent to 25 M87 effective radii), and SAURON integral field unit data within the central 2.4 kpc. Read More

We conduct the first microlensing simulation in the context of planet formation model. The planet population is taken from the Ida & Lin core accretion model for $0.3M_\odot$ stars. Read More

Sub-parsec binary massive black holes (BBHs) are long anticipated to exist in many QSOs but remain observationally elusive. In this paper, we propose a novel method to probe sub-parsec BBHs through microlensing of lensed QSOs. If a QSO hosts a sub-parsec BBH in its center, it is expected that the BBH is surrounded by a circum-binary disk, each component of the BBH is surrounded by a small accretion disk, and a gap is opened by the secondary component in between the circum-binary disk and the two small disks. Read More

Recently the commissioning APOGEE observations of the Galactic bulge reported that a significant fraction of stars ($\sim10%$) are in a cold ($\sigma_{\rm V} \approx 30$ km/s) high velocity peak (Galactocentric radial velocity $\approx 200$ km/s). These stars are speculated to reflect the stellar orbits in the Galactic bar. In this study, we use two $N$-body models of the Milky Way-like disk galaxy with different bar strengths to critically examine this possibility. Read More

We study microlensing light curves by a triple lens, in particular, by a primary star plus two planets. A four-fold degeneracy is confirmed in the light curves, similar to the close and wide degeneracy found in a double lens. Furthermore, we derive a set of equations for triple-lens in the external shear approximation. Read More

We study gravitational lensing when plasma surrounds the lens. An extra deflection angle is induced by the plasma in addition to the deflection generated by gravity. An inhomogeneous plasma distribution generates a greater effect than a homogeneous one, and may cause significant effects to be detected in low frequency radio observations (a few hundred MHz). Read More

We study three-dimensional microlensing where two lenses are located at different distances along the line of sight. We formulate the lens equation in complex notations and recover several previous results. There are in total either 4 or 6 images, with an equal number of images with positive and negative parities. Read More

We study the spatial distribution of the Fe 6.4 and 6.7 keV lines in the nuclear region of M82 using the Chandra archival data with a total exposure time of 500 ks. Read More

Using the potential from N-body simulations, we construct the Galactic bar models with the Schwarzschild method. By varying the pattern speed and the position angle of the bar, we find that the best-fit bar model has pattern speed $\Omega_{\rm p}=40\ \rm{km\ s^{-1}\ kpc^{-1}}$, and bar angle $\theta_{\rm bar}=45^{\circ}$. $N$-body simulations show that the best-fit model is stable for more than 1. Read More

Lensing flux-ratio anomalies are most likely caused by gravitational lensing by small-scale dark matter structures. These anomalies offer the prospect of testing a fundamental prediction of the cold dark matter (CDM) cosmological model: the existence of numerous substructures that are too small to host visible galaxies. In two previous studies we found that the number of subhalos in the six high-resolution simulations of CDM galactic halos of the Aquarius project is not sufficient to account for the observed frequency of flux ratio anomalies seen in selected quasars from the CLASS survey. Read More

We present a study of the luminosity density distribution of the Galactic bar using number counts of red clump giants (RCGs) from the OGLE-III survey. The data were recently published by Nataf et al. (2013) for 9019 fields towards the bulge and have $2. Read More

We study the lensing magnification effect on background galaxies. Differential magnification due to different magnifications of different source regions of a galaxy will change the lensed composite spectra. The derived properties of the background galaxies are therefore biased. Read More

We study the effects on the number counts of sub-millimetre galaxies due to gravitational lensing. We explore the effects on the magnification cross section due to halo density profiles, ellipticity and cosmological parameter (the power-spectrum normalisation $\sigma_8$). We show that the ellipticity does not strongly affect the magnification cross section in gravitational lensing while the halo radial profiles do. Read More

2012Sep
Affiliations: 1National Astronomical Observatories, Chinese Academy of Sciences, China, 2National Astronomical Observatories, Chinese Academy of Sciences, China

The masses of stars including stellar remnants are almost exclusively known from binary systems. In this work, we study gravitational microlensing of faint background galaxies by isolated neutron stars (pulsars). We show that the resulting surface brightness distortions can be used to determine the masses of neutron star. Read More

We use Schwarzschild's orbit-superposition technique to construct self-consistent models of the Galactic bar. Using $\chi^2$ minimisation, we find that the best-fit Galactic bar model has a pattern speed $\Omega_{\rm p}=60 \rm{km s^{-1} kpc^{-1}}$, disk mass $\rm{M_{\rm d}=1.0\times10^{11}M_{\odot}}$ and bar angle $\theta_{\rm bar}=20^{\circ}$ for an adopted bar mass $\rm{M_{\rm bar}=2\times10^{10}M_{\odot}}$. Read More

We demonstrate how the Syer & Tremaine made-to-measure method of stellar dynamical modelling can be adapted to model a rotating galactic bar. We validate our made-to-measure changes using observations constructed from the existing Shen et al. (2010) N-body model of the Milky Way bar, together with kinematic observations of the Milky Way bulge and bar taken by the Bulge Radial Velocity Assay (BRAVA). Read More

Since the first discovery of microlensing events nearly two decades ago, gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications. The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights. (1) Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects (MACHOs). Read More

We present measurements of the velocity dispersion profile (VDP) for galaxy groups in the final data release of the Sloan Digital Sky Survey (SDSS). For groups of given mass we estimate the redshift-space cross-correlation function (CCF) with respect to a reference galaxy sample, xi(r_p, pi), the projected CCF, w_p(r_p), and the real-space CCF, xi(r). The VDP is then extracted from the redshift distortion in xi(r_p, pi), by comparing xi(r_p, pi) with xi(r). Read More

We present a spatial analysis of the soft X-ray and H{\alpha} emissions from the outflow of the starburst galaxy M82. We find that the two emissions are tightly correlated on various scales. The O VII triplet of M82, as resolved by X-ray grating observations of XMM-Newton, is dominated by the forbidden line, inconsistent with the thermal prediction. Read More

2012Mar
Affiliations: 1College of Physical Science and Technology, Shenyang Normal University, China, 2NAOC, China, 3NAOC, China

We identify a total of 120 early-type Brightest Cluster Galaxies (BCGs) at 0.1Read More

We take a sample of 24 elliptical and lenticular galaxies previously analysed by the SAURON project using three-integral dynamical models created with Schwarzschild's method, and re-analyse them using the made-to-measure (M2M) method of dynamical modelling. We obtain good agreement between the two methods in determining the dynamical mass-to-light (M/L) ratios for the galaxies with over 80% of ratios differing by < 10% and over 95% differing by < 20%. We show that (M/L)_M2M is approximately equal to (M/L)_Sch. Read More