arXiv subjects

Peeter Tenjes

Publications and source records attributed to Peeter Tenjes.

24 records · Page 2Linked to original sources

arXiv2008

Visible and dark matter in M31 - I. Properties of stellar components

We construct a structural model of the Andromeda Galaxy, simultaneously corresponding to observed photometrical and kinematical data and chemical abundances. In this paper we present the observed surface brightness, colour and metallicity distributions, and compare them to the model galaxy. In Paper II (Tempel, Tamm & Tenjes 2007) we present similar data for the kinematics, and derive the mass distribution of the galaxy. On the basis of U, B, V, R, I and L luminosity distributions, we construct the model galaxy as a superposition of four axially symmetric stellar components: a bulge, a disc, an inner halo and an extended diffuse halo. By using far-infrared imaging data of M31 and a thin dust disc assumption, we derive dust-free surface brightness and colour distributions. We find the total absorption corrected luminosity of M31 to be L_B = (3.3+/-0.7)x10^10 L_sun, corresponding to an absolute luminosity M_B = -20.8+/-0.2 mag. Of the total luminosity, 41% (0.57 mag) is obscured from us by the dust inside M31. Using chemical evolution models, we calculate mass-to-light ratios of the components, correspoding to the colour indices and metallicities. We find the total intrinsic mass-to-light ratio of the visible matter to be M/L_B=3.1-5.8 M_sun/L_sun and the total mass of visible matter M_vis =(10-19)x10^10 M_sun. The use of the model parameters for a dynamical analysis and for determining dark matter distribution is presented in Paper II.

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arXiv2008

Visible and dark matter in M 31 - II. A dynamical model and dark matter density distribution

In the present paper we derive the density distribution of dark matter (DM) in a well-observed nearby disc galaxy, the Andromeda galaxy. From photometrical and chemical evolution models constructed in the first part of the study (Tamm, Tempel & Tenjes 2007 (arXiv:0707.4375), hereafter Paper I) we can calculate the mass distribution of visible components (the bulge, the disc, the stellar halo, the outer diffuse stellar halo). In the dynamical model we calculate stellar rotation velocities along the major axis and velocity dispersions along the major, minor and intermediate axes of the galaxy assuming triaxial velocity dispersion ellipsoid. Comparing the calculated values with the collected observational data, we find the amount of DM, which must be added to reach an agreement with the observed rotation and dispersion data. We conclude that within the uncertainties, the DM distributions by Moore, Burkert, Navarro, Frenk & White (NFW) and the Einasto fit with observations nearly at all distances. The NFW and Einasto density distributions give the best fit with observations. The total mass of M 31 with the NFW DM distribution is 1.19*10^12 M_sun, the ratio of the DM mass to the visible mass is 10.0. For the Einasto DM distribution, these values are 1.28*10^12 M_sun and 10.8. The ratio of the DM mass to the visible mass inside the Holmberg radius is 1.75 for the NFW and the Einasto distributions. For different cuspy DM distributions, the virial mass is in a range 6.9-7.9*10^11 M_sun and the virial radius is ~150 kpc. The DM mean densities inside 10 pc for cusped models are 33 and 16 M_sun pc^-3 for the NFW and the Einasto profiles, respectively. For the cored Burkert profile, this value is 0.06 M_sun pc^-3.

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arXiv2006

Line-of-sight velocity dispersions and a mass distribution model of the Sa galaxy NGC 4594

In the present paper we develop an algorithm allowing to calculate line-of-sight velocity dispersions in an axisymmetric galaxy outside of the galactic plane. When constructing a self-consistent model, we take into account the galactic surface brightness distribution, stellar rotation curve and velocity dispersions. This algorithm is applied to a Sa galaxy NGC 4594 = M 104, for which there exist velocity dispersion measurements outside of the galactic major axis. The mass distribution model is constructed in two stages. In the first stage we construct a luminosity distribution model, where only galactic surface brightness distribution is taken into account. Thereafter, in the second stage we develop on the basis of the Jeans equations a detailed mass distribution model and calculate line-of-sight velocity dispersions and the stellar rotation curve. Here a dark matter halo is added to visible components. Calculated dispersions are compared with observations along different slit positions perpendicular and parallel to the galactic major axis. In the best-fitting model velocity dispersion ellipsoids are radially elongated. Outside the galactic plane velocity dispersion behaviour is more sensitive to the dark matter density distribution and allows to estimate dark halo parameters.

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arXiv2004

Structure of visible and dark matter components of spiral galaxies at z = 0.9

We construct self-consistent light and mass distribution models for 4 distant spiral galaxies. The models include a bulge, a disk and an isothermal dark matter. We find the luminosity profiles to have much steeper cut-off than that of a simple exponential disk. We apply k-corrections and derive rest-frame B-band mass-to-light ratios of the visible components and the central densities of the dark halos; we discover no significant evolution with redshift of these parameters.

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arXiv2002

Metallicity distributions of globular cluster systems in galaxies

We collected a sample of 100 galaxies for which different observers have determined colour indices of globular cluster candidates. The sample includes representatives of galaxies of various morphological types and different luminosities. Colour indices (in most cases (V-I), but also (B-I) and (C-T1)) were transformed into metallicities [Fe/H] according to a relation by Kissler-Patig (1998). These data were analysed with the KMM software in order to estimate similarity of the distribution with uni- or bimodal Gaussian distribution. We found that 45 of 100 systems have bimodal metallicity distributions. Mean metallicity of the metal-poor component for these galaxies is <[Fe/H]> = -1.40\pm 0.02, of the metal-rich component <[Fe/H]> = -0.69 \pm 0.03. Dispersions of the distributions are 0.15 and 0.18, respectively. Distribution of unimodal metallicities is rather wide. These data will be analysed in a subsequent paper in order to find correlations with parameters of galaxies and galactic environment.

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arXiv2002

Structure and mass distribution of spiral galaxies at intermediate redshifts

Using the HST archive WFPC2 observations and rotation curves measeured by Vogt et al. (1996), we constructed self-consistent light and mass distribution models for three disk galaxies at redshifts z = 0.15, 0.90 and 0.99. The models consist of three components: the bulge, the disk and the dark matter. Spatial density distribution parameters for the components were calculated. After applying k-corrections, mass-to-light ratios for galactic disks within the maximum disk assumption are M/L_B = 4.4, 1.2 and 1.2, respectively. Corresponding central densities of dark matter halos within a truncated isothermal model are 0.0092, 0.028 and 0.015 in units M_sol/pc^3. The light distribution of galaxies in outer parts is steeper than a simple exponential disk.

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