Stellar physics and evolution galex and star formation

Дата канвертавання24.04.2016
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Kevin France, Jeffrey L. Linsky, John T. Stocke, and Cynthia S. Froning
We present the deepest ultraviolet observations of a transiting exoplanetary system ever acquired. We used the Cosmic Origins Spectrograph (COS), recently installed on the Hubble Space Telescope, to observe the HD209458 system at primary and secondary eclipse, as well as both quadrature positions. The transit observations confirm the ~8% decrease in stellar flux at the CII doublet, and we use the spectral resolving power of COS to characterize the velocity distribution of the CII atmosphere. These data also reveal an 8% decrease from SiIII for the first time. We use these results to constrain the mass-loss rate from the planet (3.2 x 1011 g/s), consistent with an exoplanetary wind that fills its Roche Lobe, or that is distributed into a cometary tail. We also present the first search for direct auroral emissions from an exoplanet. We compare models of gas giant atmospheres to the observed quadrature spectra to place constraints on the presence of a Jovian-like auroral system, and discuss implications for models of hot Jupiters.

Hélène Menager, Mathieu Barthélemy, Jean Lilensten

Laboratoire de Planétologie de Grenoble, France
Jupiter has bright aurorae due to particle precipitation in the upper atmosphere. In the FUV, the brightest emissions are those of the H Lyman-α line and of the Lyman and Werner bands of H2. These emissions provide information on the precipitating particles, which are still poorly known, and on the atmospheric conditions, which are badly constrained in polar regions. Auroral UV emissions of hot Jupiters, when detected, could similarly help constrain their atmospheric conditions and magnetospheric environment.

We will start by discussing the FUV auroral emissions of Jupiter. We use a kinetic code to describe the transport of the electrons which precipitate in the auroral atmosphere of this planet. This code allows us to calculate the excitation rates of H and H2, and the ensuing FUV emissions. Radiative transfer calculations are then carried out to calculate the intensity of the lines which emerge from the atmosphere. We will present the results of a sensitivity study which shows how the spectrum of H2 depends on the energy of the incident electrons and their angular distribution. We will propose some variable parameters which can be used in the analysis of observational spectra to constrain the auroral environment. We will then present how this modeling is adapted to describe the environment of hot Jupiters. For these planets, a lot of issues are still unresolved, like the presence of a magnetic field or the properties of incident particle fluxes. These issues are crucial to auroral processes and could be addressed by studying auroral emissions of the planets. France et al. (2010) used the COS instrument on HST to try to detect H2 auroral FUV emissions from HD 209458b but made no unambiguous detection. Atmospheric models of HD 209458b have been given by Yelle (2004) and Garcia-Muñoz (2007). They allow us to evaluate the H Lyman-α dayglow of the planet. We also estimate H and H2 FUV planetary emissions caused by the precipitation of particles, with and without an intrinsic magnetic field. We make observing facility suggestions for a future detection.


R. V. Yelle, “Aeronomy of extra-solar giant planets at small orbital distances”, Icarus, vol 170, pp.

167-179, 2004

A. Garcia Muñoz, “Physical and chemical aeronomy of HD 209458b”, Planetary and Space

Science, vol 55, pp. 1426-1455, 2007

K. France, J. T. Stocke, H. Yang, J. L. Linsky, B. C. Wolven, C. S. Froning, J. C. Green, S. N.

Osterman, Astrophysical Journal, vol 712, pp. 1277-1286, 2010


Antoniadis J.1, Barentsen G.2, Bjerkeli P.3, Dorner B.4, Dumitrache C.5, Eybl V.6, Humberset B.7, Jacimovic A.8, Kuutmann A.9, Lammer H.10, Moser H.11, Rotter T.12, Vinas Tió M.13, Xiang-Grüß M.14, Ygouf M.15

1 Greece, 2 Armagh Observatory, UK, 3 Onsala Space Observatory, Sweden, 4 CRAL - Observatoire de Lyon, France, 5 University Politehnica of Bucharest, Romania, 6 University of Vienna, Austria,

7 University of Bergen, Norway, 8 University College Utrecht, Netherlands, 9 Sweden, 10 Space Research Institute, Austrian Academy of Sciences, Austria,

11 Luxembourg, 12 University of Graz, Austria, 13 Universitat Politècnica de Catalunya, Spain,

14 Christian-Albrechts-Universität zu Kiel, Germany, 15 Laboratoire d'Astrophysique de Grenoble, France

The detection and investigation of extended hydrogen atmospheres around extrasolar planets provide very promising insights into the interaction of the host star with the planet as well as the evolution of these planets and their atmospheres.

There are different scenarios in the evolution of an Earth-like planet, during which hydrogen coronae can occur. In the presence of strong stellar activity, the planetary exosphere can be affected significantly leading to the production of highly energetic neutral atoms (ENA). By measuring the size of the extended atmosphere and determining the velocities of hydrogen atoms, conclusions can be drawn in respect to the origin of these features.

Due to the large number of M-type stars in our neighborhood and their comparably long periods of strong stellar activity, M-type stars represent the most promising candidates for the detection of ENAs and the subsequent study of the interaction between the host star and the planets' atmosphere as well as the evolution of the planet. The low mass of M-type stars also makes them preferable targets to observe extended hydrogen clouds around planets with a mass as low as one Earth mass.

This method can be understood as a new approach for the research of star-planet interaction and planet evolution.



Sil'chenko Olga K.

Sternberg Astronomical institute of the MSU,Russia
The nature of UV-radiation in galaxies of different morphological types will be reviewed. The UV-excess in massive elliptical galaxies which have predominantly old stellar populations is traditionally explained by the contribution of low-mass stars at very late, poorly known stages of evolution -- by so called `AGB-manque' stars or by the populations of extended horizonthal branch. However recent results from the GALEX survey for a rich sample of nearby ellipticals have also demonstrated probable traces of recent star formation in a third of all ellipticals observed. In spiral galaxies the extended UV-disks have been discovered by the GALEX; they are certainly illuminated by the current star formation, but what has provoked star formation in the area of very low gas density, beyond the distribution of older stars, is a puzzle yet. A separate very interesting problem which can be solved only in the UV spectral range, is a search for `missing baryons' -- for the warm gas which can be detected through the absorption lines of highly ionized O and C in the spectra of background sources (quasars). Some results are already reported, but even more remains to be done relating this topic.

Linsky Jeffrey

M. Chavez, E. Bertone and A. Bressan

In this talk I will briefly address the main topics that, in my opinion, have substantially motivated the development of the technique called evolutionary population synthesis and that, to some extent, are still open. These are (a) the rising branch of the Far-UV energy distribution of Elliptical Galaxies, (b) The age metallicity degeneracy and the UV spectrum as a (complementary) tool to break it, (c) The UV properties of distant red galaxies and (d) the stellar libraries currently used in the modeling of the integrated properties of evolved populations. In addition to historical remarks in these four branches and an updated view of their current status, I will comment on some recent investigations developed by our group that might help in understanding the global UV properties of aged stellar populations.


Gnedin Yu.N.

Central Astronomical Observatory at Pulkovo, Russia
I present the review of basic methods of measurements of magnetic fields with application to accreting supermassive black holes in UV spectral range/ The problem of connection between t jet and accretion disk is discussed. The expected results of UV polarimetric observations of QSO and AGN are presented in this talk. I consider the new aspects of UV polarimetry of AGN: (a) the strong dependence of UV polarization on the rotation rate of a supermassive black hole; (b) the principal possibility to use polarimetric observations for testing cosmological models.

Chris Martin

California Institute of Technology. USA
The Galaxy Evolution Explorer (GALEX) continues its surveys of the ultraviolet sky. GALEX surveys have supported the following galaxy evolution investigations: calibrating UV as a star formation rate tracer, using wide and deep surveys to measure star formation history, studying the evolution of dust extinction and metallicity, selecting and analyzing galaxies in transitory states, finding local analogs to Lyman Break Galaxies, probing and time-dating star formation in a wide variety of physical regimes. Our continuing mission is focussed on relating star formation history and galaxy evolution paths to the properties of dark matter halos and their assembly history, and on beginning to relate the evolution of galaxies to that of black holes and the intergalactic medium. GALEX has proven that the UV is an ideal band to find and map star formation in low mass, low density objects, and potentially in primordial gas. GALEX has made a number of new and exciting discoveries, including winds from AGB stars glowing in the UV, extended star forming disks, analogs to high redshift galaxies, stellar tidal disruption flares from otherwise inactive massive black holes, and supernova break-out shocks. With future UV missions it may be possible to map emission from the intergalactic and circum-galactic medium, and make a definitive connection between galaxy evolution and the cooling, accretion, heating, and enrichment of gas in the cosmic web.


Evgeny Gorbikov and Noah Brosch

The Wise Observatory and the Raymond and Beverly Sackler School of Physics and Astronomy, the Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
We present preliminary results of an optical two-colour CCD survey of the North Celestial Cap (NCCS) combined with UV observations. The NCCS primary aim was to obtain good photometric and astrometric data for the region from the Pole ( = 90 ) to  = 80 in support of the TAUVEX mission. This region, at galactic latitudes from ~17 to ~37 , has poor coverage in modern CCD-based surveys.

The observations are performed with the Wise Observatory one-meter reflector and with a new mosaic CCD camera (LAIWO) that images in the Johnson-Cousins R and I bands a one-square-degree field with sub-arcsec pixels. The images are treated using IRAF and SExtractor to produce a final catalogue of sources. The astrometry, based on the USNO-A2.0 catalogue, is good to . 1 arcsec and the photometry is good to ~0.1 mag for point sources brighter than R=20.2 or I=19.1 mag. The limiting magnitudes of the survey, defined at photometric errors smaller than 0.15 mag, are 20.7 mag (R) and 19.7 (I). We separate stars from non-stellar objects based on the object shapes in the R and I bands, attempting to reproduce the SDSS star/galaxy dichotomy. The completeness test indicates that the catalogue is complete to the limiting magnitudes stated above. The NCCS sky coverage today is ~70% of the planned coverage. The expected total number of distinct objects in NCCS is ~1, 500, 000.

Here we present preliminary results for ~10% of the survey area where our R and I magnitudes are combined with GALEX FUV and NUV photometry. We discuss issues of the galactic extinction and the galaxy clustering in the color-color diagrams.

Rampazzo R.1, Marino A2., Bianchi L.2, Annibali F.1, Bressan A1. Buson, L.M. 1 Clemens M. 1, Panuzzo P3, Zeilinger, W. 4

1 - INAF-Osservatorio Padova, Italy

2 - . JHU, Baltimore, USA

3 - CEA, Saclay, France

4 - IfA, Univ. Wien, Austria
Early-type galaxies (ETGs) are considered the fossil evidence of the process of galaxy evolution. However, evidence are accumulating that rejuvenation of the ETGs stellar populations may be triggered both by accretion events and by the inner secular evolution.

We are performing a comprehensive, multi-wavelength study of 65 nearby ETGs, mostly located in low density environments. Aimimg at improving our understanding of the evolution of ETGs, we are extending the study of their spectral energy distribution to the far UV region, sensitive to the presence of young stellar populations.

We present here the GALEX FUV and NUV study of 40 out of 65 ETGs in the original sample. We present and model the secular evolution in ETGs with ring/arm-like structures detected in the far UV. The Far UV data set is complemented by optical and Mid Infrared (Spitzer-IRS) observations.

Yuri A. Shchekinov1, Biman B. Nath2

1 - Southern Federal University, Russia

2 - Raman Research Institute, Bangalore, India

The presence of metals in the intergalactic (IG) space suggests that dust particles may also exist there. It is clear thought that the dust abundance in the IG mechanism is small as the corresponding reported extinction is only E(B-V)~0.1. Even in this negligible amount dust grains can considerably affect thermodynamics of the IG gas through photoelectric heating. The key question is therefore what exact fraction of dust particles is expelled from galaxies under their activity, what are dust properties when they reach true intergalactic medium. We discuss here dust transport mechanism, destruction and survival of dust drains. We argue that intergalactic dust is generally much lighter, i.e. they are smaller in size, then dust in galaxies.


Hoversten Erik (Penn State), Gronwall Caryl (Penn State), Vanden Berk Daniel (St. Vincent's College), Roming Peter (Penn State)
The UV/Optical Telescope (UVOT) onboard the Swift Gamma-Ray Burst Explorer satellite occupies a niche in UV parameter space (having a smaller PSF than GALEX while the UVOT field of view is larger than those of HST instruments). It is ideally suited for studies of galaxy evolution, two of which are described here. UVOT observed the Extended Chandra Deep Field South for a total of 568,000 seconds split between the uvw2 (2030 A), uvm2 (2231 A), uvw1 (2634 О‘) and u (3501 A) filters. Galaxy number counts cover a range of AB magnitudes from 21 - 26 in uvw2 to 20 - 24.5 in u, bridging the gap between the GALEX NUV number counts (Xu, et al. 2005) and HST STIS NUV number counts (Gardner, Brown, & Ferguson 2000) and are consistent with both suggesting evolution in the UV luminosity function of galaxies. UVOT observed M81 and its companion galaxy, Holmberg IX. We combine UVOT imaging in the uvw2, uvm2, and uvw1 filters is combined with imaging in the u, g, r, i, and z bands from the Sloan Digital Sky Survey to extend the SED coverage of the star forming regions. We show the colors and derived ages of individual star forming regions, UV surface brightness profiles, and pixel by pixel fits of the properties of the stellar populations in M81 and Homberg IX. These results are in agreement with an interaction between M81 and M82 200 Myr ago, a tidal dwarf origin for Holmberg IX, and a Milky Way extinction law for both galaxies.

Vasiliev Evgenii1,Sethi Shiv K.2, Nath Biman B. 2

1 - Southern Federal University, Russia

2 - Raman Research Institute, Bangalore, India

We constrain the spectrum of the cosmic ultraviolet background radiation by fitting the observed abundance ratios carbon ions at $z\sim 2\hbox{--}3$ with those expected from different models of the background radiation. We use the recently calculated modulation of the background radiation between 3 and 4 Ryd due to resonant line absorption by intergalactic HeII, and determine the ratios of CIII to CIV expected at these redshifts, as functions of metallicity, gas density and temperature. Our analysis of the observed ratios shows that 'delayed reionization' models, which assume a large fraction of HeII at $z\sim3$, is not favoured by data. Our results suggest that HeII reionization was inhomogeneous and extended to redshifts as low as $z\sim2.5$.


Ivanchik Alexander V.1, Varshalovich Dmitry A. 1, Balashev Sergei A.1,Petitjean Patrick2

1 - Ioffe Physical-Technical Institute RAS, Russia

2 - IAP CNRS France
We discuss some possibilities of observations of the baryon content in the low Universe: researches of the hot gas in the low Universe from a OVI-NeVIII survey and DLA-systems survey for z<2.



Indian Institute of Astrophysics, Bangalore 560 034. INDIA

Astrophysical systems of various types are known to possess copious quantities of dust, which differ in their chemical compositions and also in their morphology, both of which are determined by the environment and the process by which the grain grows. While the light absorption properties are largely determined by the composition, the scattering properties of substances are determined also by the size of the grain and also by the roughness of the surface. We will consider a model, in which the grain size distribution is described by a distribution function of the type:

P(a) = 0 for a0

= Na-x exp[-(a/r0)y] , for a≥ a0 (1)

where N is a normalizing constant for the probability P(a)da that the grain has a radius, lying between a and a+da. In the above distribution, a0 describes the minimum size of the grain, i.e. the size of the critical nucleus and another length scale, r0 describes approximately the radius, beyond which the probability approaches zero very rapidly. The factor a-x is chosen to account for the scaling law kind of dependence that is found observationally. Thus a0 and r0 give the typical range within which the grains of different radii can be found to exist. While the probability P(a) tends to zero for a>>r0, the parameter y describes as to how fast does this fall to zero take place. The four parameters, involved in the description of P(a) can be related to the details of the grain formation and destruction process. From the theories of scattering it can be shown that the scattering cross section for any wave vector of scattering ks is given by,

σ(ks) = [k4(nr2-1)2/ks6] ∫ [cos(ksa) – (ksa)sin(ksa)]2P(a)da (2)

where k = (2π/λ) , λ being the wave length of light. It can be seen from equations (1) and (2) that σ(ks) involves two dimensionless quantities, (ksa0) and (ksr0) and can be expressed in terms of confluent hypergeometric series involving the above dimensionless quantities for which we present the asymptotic expansions. Computations for realistic situations will be presented, for wave length of light being in the ultraviolet range. The result, it is clear will contain admixture of Rayleigh and diffractive parts, which will be delineated for the purpose of inversion, as is needed for extracting the values of the parameters a0, r0, x and y.

Jesus Maiz Apellaniz, Instituto de Astrofisica de Andalucia
WFPC2 was the last instrument aboard HST with FUV wide-field imaging capabilities not subject to bright-object limits. Before the instrument was brought back to Earth by the SM4 astronauts in May 2009, we used it to observe five Galactic open clusters and H II regions in multiple filters between the FUV and the I band. Those data represent the highest angular-resolution images in the FUV ever obtained of objects of such type. We will present our first results, including the first subarcsecond-resolution image of a Galactic reflection nebula in the FUV.

Brad Tucker, Mt. Stromlo Observatory, ANU
The use of type Ia supernova (SNe Ia) as standard candles has shifted from not just simply testing whether the Universe is accelerating, but what in fact is the cause of the mysterious dark energy. Determining the dark energy equation of state to better than 10% is the aim in current supernova cosmology projects, as it will help to distinguish between various cosmological models. However, we still lack a clear understanding of the SNe Ia progenitor systems, and their use in cosmology has provide a variety of systematic problems. Recently though, the use of ultraviolet photometry has helped us to eliminate possible progenitor system models. Furthermore, the analyzing of the host galaxies of SNe Ia's has utilized UV photometry to measure the dust content and star formation history of the host galaxy. I will present these results from two new papers that without the ultraviolet, would not have been possible.


Mychelkin E.G., Denisyuk E.K.

Fesenkov Astrophysical Institute, Nat. Center of Space Researches&Technologies, Almaty 050020 Kazakhstan
Some theoretical and observational aspects of dark matter (DM) phenomenon in the Universe are discussed in relation with the proposed tachyon neutrinos background as a realistic approach to DM. Then the expected scale for galactic DM ‘haloes’ is about (0.3 – 3) Mpc to be in concordance with empirical law of the surface mass-density constancy exposed recently for a big array of spiral galaxies (Donato F. et al., arXiv: astro-ph/0904.4054 (2009)). To perform the corresponding astronomical UV observations of widespread masses (including DM) around galaxies the special long-slit spectrograph method is presented to be applied for measuring the saturation effect of rotation curves in galaxies on the grounds of Ly-alpha emission line registration.
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