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We have investigated chemical evolution in the young universe by analysing the detailed chemical enrichment pattern of a metal-rich galaxy at high redshift. The recent detection of over 20 elements in the gas-phase of a damped Lyman-alpha…

Astrophysics · Physics 2009-11-10 Yeshe Fenner , Jason X. Prochaska , Brad K. Gibson

We study the statistical properties (such as shape and spin) of high-z halos likely hosting the first (PopIII) stars with cosmological simulations including detailed gas physics. In the redshift range considered ($11 < z < 16$) the average…

Cosmology and Nongalactic Astrophysics · Physics 2013-01-03 Rafael S. de Souza , Benedetta Ciardi , Umberto Maio , Andrea Ferrara

We present an analysis of the space motions of 742 subdwarf stars based on the sample of Carney et al. (1994, CLLA). Hipparcos parallaxes, TYC2+HIP proper motions and Tycho2 proper motions were combined with radial velocities and…

Astrophysics · Physics 2009-11-10 M. I. Arifyanto , B. Fuchs , H. Jahreiss , R. Wielen

The physical structure of the envelopes around a sample of fourteen massive (1000-100,000 solar L) young stars is investigated on 100- 100,000 AU scales using maps and spectra in submillimeter continuum and lines of C17O, CS and H2CO. The…

We investigate the fundamental plane (FP) of selected early-type (ETG) member galaxies of the galaxy cluster PLCK G287.0+32.9 ($ z_c = 0.3833 $), exploring also four-dimensional hyperplane extensions. We measure ETGs structural parameters…

Scalar-tensor gravity models are among the prime candidates to explain cosmic acceleration, and compact stars provide unique laboratories for testing such theories. Predictions of scalar-tensor gravity in compact stars can be examined…

High Energy Astrophysical Phenomena · Physics 2025-10-08 Fahimeh Rahimi , Zeinab Rezaei , Adamu Issifu

In this paper, new bounds on possible variations of the fine structure constant, $\alpha$, for a class of runaway dilaton models are performed. By considering a possible evolution with redshift, $z$, such as…

Cosmology and Nongalactic Astrophysics · Physics 2021-11-01 R. F. L. Holanda , L. R. Colaço , R. S. Gonçalves , J. S. Alcaniz

We present HI synthesis observations of the nearby dwarf galaxy IC 2574 (a member of the M81 group of galaxies) made with the NRAO Very Large Array at high spatial and velocity resolution (95 pc x 2.6 km/s). The VLA HI observations show a…

Astrophysics · Physics 2009-10-31 Fabian Walter , Elias Brinks

Using six different parametrizations of the quantum hadrodynamics (one of which is original), I study how different values of the symmetry energy slope ($L)$ affect some microscopic and macroscopic properties of neutron stars, such as the…

Nuclear Theory · Physics 2024-07-26 Luiz L. Lopes

We present a detailed spectroscopic analysis of the stars with helium-dominated spectra in the ESO Supernova Ia Progenitor Survey (SPY). Atmospheric parameters, masses, and abundances of trace hydrogen are determined and discussed in the…

Astrophysics · Physics 2007-06-21 B. Voss , D. Koester , R. Napiwotzki , N. Christlieb , D. Reimers

The large separations between the oscillation frequencies of solar-like stars are measures of stellar mean density. The separations have been thought to be mostly constant in the observed range of frequencies. However, detailed…

Solar and Stellar Astrophysics · Physics 2015-05-20 M. Yıldız , Z. Çelik Orhan , C. Kayhan

We analyze the structure of 15 protocluster forming regions in the Milky Way using their $1.3$ mm continuum emission maps from the ALMA-IMF large program. The analysis of the clouds structure is performed using the delta-variance spectrum…

Astrophysics of Galaxies · Physics 2023-07-04 Sami Dib

We present dense grids of stellar models suitable for comparison with observable quantities measured with great precision, such as those derived from binary systems or planet-hosting stars. We computed new Geneva models without rotation at…

Solar and Stellar Astrophysics · Physics 2015-06-03 N. Mowlavi , P. Eggenberger , G. Meynet , S. Ekstrom , C. Georgy , A. Maeder , C. Charbonnel , L. Eyer

We use the strong nebular lines of O III, 5007 A and 4959 A, to set a robust upper limit on the time dependence of the fine structure constant. We find |alpha^{-1} d alpha(t)/dt | < 2*10^{-13} yr, corresponding to Delta alpha/alpha(0) =…

Astrophysics · Physics 2009-09-29 John N. Bahcall , Charles L. Steinhardt , David Schlegel

We confront the star formation rate in different dark matter (DM) models with UV luminosity data from JWST up to $z\simeq25$ and legacy data from HST. We find that a transition from a Salpeter population to top-heavy Pop-III stars is likely…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-07 John Ellis , Malcolm Fairbairn , Juan Urrutia , Ville Vaskonen

We investigate the relationship between the star formation rate per unit area and the surface density of the ISM (the local Kennicutt-Schmitt law) using a simplified model of the ISM and a simple estimate of the star formation rate based on…

Astrophysics of Galaxies · Physics 2015-05-13 C. L. Dobbs , J. E. Pringle

With the plethora of detailed results from heliospheric missions and at the advent of the first mission dedicated IBEX, we have entered the era of precision heliospheric studies. Interpretation of these data require precision modeling, with…

Astrophysics · Physics 2008-12-05 S. Tarnopolski , M. Bzowski

Using H-alpha spectra of 114 rest-frame UV-selected galaxies at z~2, we compare inferred star formation rates (SFRs) with those determined from the UV continuum luminosity. After correcting for extinction using standard techniques based on…

We determine the primordial helium mass fraction Yp using 93 spectra of 86 low-metallicity extragalactic HII regions. This sample constitutes the largest and most homogeneous high-quality data sets in existence for the determination of Yp.…

Astrophysics · Physics 2008-11-26 Y. I. Izotov , T. X. Thuan , G. Stasinska
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