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We probe the spatial distribution of the [C ii] μm fine-structure emission and its association with neutral and molecular gas in a 5′.7 × 3′.7 (∼3.3 × 2.1 pc2) region of the M17 SW nebula. Comparison of velocity-resolved [C ii] emission maps with other atomic and molecular tracers is possible for the first time with the dual band receiver GREAT on board the SOFIA airborne telescope. We detected [C ii] emission in a much broader velocity range than the CO-lines (Pérez-Beaupuits et al. 2012). Only [C ii] narrow channel maps at intermediate velocities (between 10 and 24 kms) show correlations with other molecular gas components, supporting a clumpy cloud scenario. At lower (< 10 kms) and higher (>24 kms) velocities instead, we see more than 60% of the region mapped in [C ii] that is not associated with other tracers of star-forming material, the so called “CO-dark” gas. Interaction with winds and outflows lead to substantial excitation of [C ii] emitting gas, so that ablation and shock-interaction have to be taken into account to model the observed [C ii] emission.
We present a kinematical study of the marginally edge-on galaxy ESO 379-006. With Fabry-Perot spectroscopy at Hα we obtain velocity maps, the radial velocity field, and position-velocity diagrams parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the galaxy and discuss the role of projection effects. The twisting of isovelocities in the radial velocity field of the disk of ESO 379-006 as well as a kinematical asymmetry found in the position-velocity diagrams parallel to the minor axis suggest the existence of non-circular motions that can be modeled by including a radial inflow besides the rotation motion. Extraplanar Diffuse Ionized gas was detected in this galaxy both from the images and from its kinematics. It is possible that the diffuse gas is lagging in rotation.
In a thermally bistable medium, cold, dense gas is separated from warm, rarified gas by thin phase transition layers, or fronts, in which radiative heating/cooling, thermal conduction, and convection of material are balanced. While these fronts have received only scant attention in the literature, and are not resolved by most current numerical simulations, they have been shown to have important ramifications for transport processes and structure formation in the diffuse interstellar medium. Here, we discuss calculations of their hydrodynamic and magnetohydrodynamic stability properties.
We present a preliminary analysis of the self-absorbed [CII]-spectra observed with SOFIA/GREAT towards NGC 2024. Together with the detected [13CII] hyperfine satellites, the observed spectra require surprisingly high column densities of C+, both in the warm core and the foreground absorption component. Such high column densities are a challenge to explain with present state-of-the-art PDR models of the UV/molecular cloud interaction.
This work applied Chinese Spectral Radioheliograph(CSRH) to simulate the quiet Sun to produce the radio image. Then, we simulate a point source, and make all antennas have a typical phase error(5°) to calculate the dynamic range. It is found that the dynamic range agrees with the theoretical value. The image processing and simulated results are presented.
We present an ongoing survey with the Nançay Radio Telescope at L-band. The targeted area is 74° ≲ l < 150° and 3.5° < |b| < 5°. This survey is characterized by a long integration time (18 min), large bandwidth (512 MHz) and high time and frequency resolution (64 μs and 0.5 MHz) giving a nominal sensitivity limit of 0.055 mJy for long period pulsars. This is about 2 times better than the mid-latitude HTRU survey, and is designed to be complementary with current large scale surveys. This survey will be more sensitive to transients (RRATs, intermittent pulsars), distant and faint millisecond pulsars as well as scintillating sources (or any other kind of radio faint sources) than all previous short-integration surveys.
We systematically investigated the climate of water-rich terrestrial planets with a negative feedback mechanism of carbonate-silicate geochemical cycle against the climate under various obliquities and semi-major axes. We found that, while the permanent ice-cap mode (partially ice-covered throughout the year) and the seasonal ice-cap mode (partially ice-covered seasonally) exist stably at low obliquity conditions, the ranges of semi-major axis for these climate modes shrink and finally disappear with an increase of obliquity. When carbonate-silicate geochemical cycle is taken into account, the ranges of semi-major axis for all the climate modes expand at any obliquities, compared with the cases without carbonate-silicate geochemical cycle, indicating that the carbonate-silicate geochemical cycle strongly stabilizes the climate for the planets with any obliquities inside the habitable zone.
We present detailed study of the physical properties of the molecular gas in a sample of 18 gas-rich early-type galaxies -ETGs- from the ATLAS3D sample. Our goal is to better understand the star formation processes occurring in those galaxies, starting in this work by determining the properties of their molecular star-forming gas. Such study has never been performed before for ETGs and open a new window for exploring the star formation processes in the Universe. We use here the 12CO(1-0, 2-1), 13CO(1-0, 2-1), HCN(1-0) and HCO+(1-0) transitions already obtained (Krips et al. 2010 and Crocker et al. 2012 and new detections of the 12CO(3-2) line that we present too (see Bayet et al. 2012, re-submitted). From this dataset, we derive the average H2 kinetic temperature, H2 volume density and column density of the emitting gas using a non-Local Thermodynamical Equilibrium theoretical approach. For most of the gas-rich ETGs included in our sample, the CO transitions can be reproduced by gas kinetic temperatures between 10-20 K, densities of 103−4 cm−3 and CO column densities of 1018–20 cm−2. Since the CO lines trace different physical conditions than those required to emit the HCN and HCO+ lines, they are treated separately. The physical parameters corresponding to the HCN and HCO+ gas component suffer from large uncertainties and have to be considered as indicative only. In this study, for the first time, we also compare the predicted CO spectral line energy distributions of our gas-rich ETGs and their gas properties with those of a sample of nearby well-studied disc galaxies. The gas excitation conditions in 12/18 early-type galaxies appear analogous to those in the center fo Milky Way, hence the star formation activity driving these conditions may be of a similar strength and nature. The conclusions drawn have to be nevertheless considered carefully since they are based only on a limited number of observations. We show from our models that the 12CO(6-5) line emission is particularly useful for improving these results.
The near-infrared (NIR) spectral range (2–5 μm) contains a number of interesting features for the study of the interstellar medium. In particular, the aromatic and aliphatic components in carbonaceous dust can be investigated most efficiently with the NIR spectroscopy. We analyze NIR spectra of the diffuse Galactic emission taken with the Infrared Camera onboard AKARI and find that the aliphatic to aromatic emission band ratio decreases toward the ionized gas, which suggests processing of the band carriers in the ionized region.
We present parsec-scale interferometric maps of HCN(1-0) and HCO+(1-0) emission from dense gas in the star-forming region 30Dor10, obtained using the Australia Telescope Compact Array. This extreme star-forming region, located in the Large Magellanic Cloud, is characterized by a very intense ionizing radiation field and sub-solar metallicity, both of which are expected to affect molecular cloud structure. We detect 13 clumps of dense molecular gas, some of which are aligned in a filamentary structure. Our analysis of the clump properties shows that they have similar mass but slightly wider linewidths than clumps detected in other LMC star-forming regions.
The Inflativerse is a mobile planetarium run by volunteers lead by the Physics and Astronomy departments at the University of Nottingham. This is a new project set up in 2011 to offer free of charge planetarium shows and activities for schools and public events.
Feedback processes from massive stars plays a critical role in their formation, destroy the molecular clouds in which they are born and shape the evolution of galaxies. In this talk I will discuss our recent 3D AMR simulations that are the first to include the coupled feedback effects of protostellar outflows combined with protostellar heating and radiation pressure feedback and magnetic fields, in a single computation and their effects on the infalling dusty gas in the surrounding environs of the accreting core envelope. These simulations will address the detailed effects of feedback on the formation of high mass stars and massive clusters with implications for the IMF.
KS 1741–293 is a transient neutron star low-mass X-ray binary that is located at an angular distance of ≃20′ from the Galactic center. We map out the historic activity of the source since its discovery in 1989, characterize its most recent X-ray outbursts observed with Swift (2007, 2008, 2010, and 2011), and discuss its quiescent X-ray properties using archival Chandra data. KS 1741–293 is frequently active, exhibiting outbursts that typically reach a 2–10 keV luminosity of LX ≃ 1036 (D/6.2 kpc)2 erg s−1 and last for several weeks–months. However, Swift also captured a very short and weak accretion outburst that had a duration of ≲4 days and did not reach above LX ≃ 5×1034 (D/6.2 kpc)2 erg s−1. The source is detected in quiescence with Chandra at a 2–10 keV luminosity of LX ≃ 2.5×1032 (D/6.2 kpc)2 erg s−1.
It is shown with a particle simulation that the outer gap can be reproduced under a few simple assumptions. The simulation includes just the first principles, namely Maxwell's equations, a relativistic equation of motion with radiation drag, and electron-positron pair creation. We also suggest that the Y-point (the open-close boundary in the equator) is likely to be a place of heating and acceleration of plasma, and therefore it would cause high-energy emission. The dead zone along the separatrix of the oppositely directed current is found in the middle latitude region, which separates the outer gap and the polar cap accelerators.
Through out the ancient history, Chinese astronomers had made tremendous achievements. Since the main purpose of the ancient Chinese astronomy was to study the correlation between man and the universe, all the Emperors made ancient Chinese astronomy the highly regarded science throughout the history. After a brief introduction of the achievement of ancient Chinese astronomy, I describe the beginnings of modern astronomy research in China in the 20th century. Benefiting from the fast development of Chinese economy, the research in astronomy in China has made remarkable progress in recent years. The number of astronomers has doubled in the past ten years, and the number of graduate students has grown over 1300. The current budget for astronomy research is ten times larger than that ten years ago. The research covers all fields in astronomy, from galaxies to the Sun. The recent progress in both the instruments, such as the Guo Shoujing's telescope, a Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), and the theoretical research will be briefly presented. The ongoing and future projects on the space- and ground-based facilities will be described, including the Five Hundred Meter Aperture Spherical Radio Telescope (FAST), “Chang E” (Lunar mission) project, Hard X-ray Modulate Telescope (HXMT), DArk Matter Particle Explorer (DAMPE), Deep Space Solar Observatory (DSO), Chinese Antarctic Observatory (CAO), 65m steerable radio telescope, Chinese Spectral Radioheliogaph (CSRH) etc.
It is generally accepted that local elliptical galaxies assembled most of their mass in a burst of star formation between 1 < z < 3, yet today, their star formation has been almost entirely quenched. In order to constrain this quenching mechanism, we measure Hα line emission in galaxies sorted by multiple galaxy properties as a function of redshift to what galaxy parameter best predicts quiescence. This is done for samples of the most massive, most luminous, and galaxies with the highest velocity dispersion both locally (0.05 < z < 0.07 in the SDSS) and at high redshift (0.7 < z < 1.5 in 3D-HST). It is demonstrated through spectral stacking that velocity dispersion results in the lowest Hα line equivalent width both locally and at high redshift. The spatial distribution of the emission line flux is available from grism spectroscopy: the line flux from the high dispersion stack is centrally peaked and thus likely associated with AGN activity rather than star formation, strengthening this conclusion. Since velocity dispersion may also be the best predictor of halo mass (Wake et al. 2012), this may imply that the quenching mechanism is directly related to halo mass.
This paper gives an brief overview of the structure of hypothetical strange quarks stars (quark stars, for short), which are made of absolutely stable 3-flavor strange quark matter. Such objects can be either bare or enveloped in thin nuclear crusts, which consist of heavy ions immersed in an electron gas. In contrast to neutron stars, the structure of quark stars is determined by two (rather than one) parameters, the central star density and the density at the base of the crust. If bare, quark stars possess ultra-high electric fields on the order of 1018 to 1019 V/cm. These features render the properties of quark stars more multifaceted than those of neutron stars and may allow one to observationally distinguish quark stars from neutron stars.
MAHALO-Subaru (MApping HAlpha and Lines of Oxygen with Subaru) is our on-going large programme which aims to investigate how the star forming activities in galaxies are propagated as a function of time, mass, and environment. We are targeting 10 clusters and proto-clusters at 0.4<z<2.6, and two general fields (GOODS-N and SXDF-CANDELS) with Suprime-Cam and MOIRCS by utilizing our unique sets of narrow-band filters. The narrow-band imaging can map out star forming galaxies with the redshifted Halpha and/or [OII] emission lines from our targets, and thus providing relatively unbiased views of star forming activities across time and environment. We have almost completed narrow-band imaging of our targets, and found that star forming activity is very high even in the proto-cluster cores (z≳1.5), and that the peak of star formation is shifted outwards with time, indicating the inside-out formation of clusters. Moreover, we have identified many “red” emitters especially in high density regions at z>2, which suggests that the mode of star formation and/or the activation of AGN are dependent on environment, and thus holding the key to the environmental effects at the early stage of cluster galaxies formation and evolution.
What happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand which mechanisms are involved in this transformation. We find that the dEs in the outer parts of Virgo have rotation curves with shapes and amplitudes similar to late-type galaxies of the same luminosity (Fig. 1). These dEs are rotationally supported, have disky isophotes, and younger ages than those dEs in the center of Virgo, which are pressure supported, often have boxy isophotes and are older (Fig. 1). Ram pressure stripping, thus, explains the properties of the dEs located in the outskirts of Virgo. However, the dEs in the central cluster regions, which have lost their angular momentum, must have suffered a more violent transformation. A combination of ram pressure stripping and harassment is not enough to remove the rotation and the spiral/disky structures of these galaxies. We find that on the the Faber-Jackson and the Fundamental Plane relations dEs deviate from the trends of massive elliptical galaxies towards the position of dark matter dominated systems such as the dwarf spheroidal satellites of the Milky Way and M31. Both, rotationally and pressure supported dEs, however, populate the same region in these diagrams. This indicates that dEs have a non-negligible dark matter fraction within their half light radius.
International activities for astronomy began when Mongolia joined the IAU at the General Assembly held in Prague in August 2006, because space scientists, astronomers and researchers in Mongolia are coming to understand that astronomy can help Mongolian socioeconomic development. For instance, astronomy can increase general interest and encourage public engagement in the sciences.