arXiv subjects

Antti Tamm

Publications and source records attributed to Antti Tamm.

15 recordsLinked to original sources

arXiv2021

The Corona Borealis supercluster: connectivity, collapse, and evolution

We present a study of the Corona Borealis (CB) supercluster. We determined the high-density cores of the CB and the richest galaxy clusters in them, and studied their dynamical state and galaxy content. We determined filaments in the supercluster to analyse the connectivity of clusters. We compared the mass distribution in the CB with predictions from the spherical collapse model and analysed the acceleration field in the CB. We found that at a radius $R_{\mathrm{30}}$ around clusters in the CB (A2065, A2061, A2089, and Gr2064) (corresponding to the density contrast $Δρ\approx 30$), the galaxy distribution shows a minimum. The $R_{30}$ values for individual clusters lie in the range of $3 - 6$ $h^{-1}$ Mpc. The radii of the clusters (splashback radii) lie in the range of $R_{\mathrm{cl}} \approx 2 - 3$ $R_{\mathrm{vir}}$. The projected phase space diagrams and the comparison with the spherical collapse model suggest that $R_{\mathrm{30}}$ regions have passed turnaround and are collapsing. Galaxy content in clusters varies strongly. The cluster A2061 has the highest fraction of galaxies with old stellar populations, and A2065 has the highest fraction of galaxies with young stellar populations. The number of long filaments near clusters vary from one at A2089 to five at A2061. During the future evolution, the clusters in the main part of the CB may merge and form one of the largest bound systems in the nearby Universe. Another part of the CB, with the cluster Gr2064, will form a separate system. The structures with a current density contrast $Δρ\approx 30$ have passed turnaround and started to collapse at redshifts $z \approx 0.3 - 0.4$. The comparison of the number and properties of the most massive collapsing supercluster cores from observations and simulations may serve as a test for cosmological models.

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arXiv2021

The role of stochastic and smooth processes in regulating galaxy quenching

Galaxies can be classified as passive ellipticals or star-forming discs. Ellipticals dominate at the high end of the mass range, and therefore there must be a mechanism responsible for the quenching of star-forming galaxies. This could either be due to the secular processes linked to the mass and star formation of galaxies or to external processes linked to the surrounding environment. In this paper, we analytically model the processes that govern galaxy evolution and quantify their contribution. We have specifically studied the effects of mass quenching, gas stripping, and mergers on galaxy quenching. To achieve this, we first assumed a set of differential equations that describe the processes that shape galaxy evolution. We then modelled the parameters of these equations by maximising likelihood. These equations describe the evolution of galaxies individually, but the parameters of the equations are constrained by matching the extrapolated intermediate-redshift galaxies with the low-redshift galaxy population. In this study, we modelled the processes that change star formation and stellar mass in massive galaxies from the GAMA survey between z~0.4 and the present. We identified and quantified the contributions from mass quenching, gas stripping, and mergers to galaxy quenching. The quenching timescale is on average 1.2 Gyr and a closer look reveals support for the slow-then-rapid quenching scenario. The major merging rate of galaxies is about once per 10~Gyr, while the rate of ram pressure stripping is significantly higher. In galaxies with decreasing star formation, we show that star formation is lost to fast quenching mechanisms such as ram pressure stripping and is countered by mergers, at a rate of about 41% Gyr$^{-1}$ and to mass quenching 49% Gyr$^{-1}$. (abridged)

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arXiv2020

Properties of brightest group galaxies in cosmic web filaments

Context. The cosmic web, a complex network of galaxy groups and clusters connected by filaments, is a dynamical environment in which galaxies form and evolve. However, the impact of cosmic filaments on the properties of galaxies is difficult to study because of the much more influential local (galaxy-group scale) environment. Aims. The aim of this paper is to investigate the dependence of intrinsic galaxy properties on distance to the nearest cosmic web filament, using a sample of galaxies for which the local environment is easily assessable.} Methods. Our study is based on a volume-limited galaxy sample with $M_\mathrm{r}$ $\leq -19$ mag, drawn from the SDSS DR12. We chose brightest group galaxies (BGGs) in groups with two to six members as our probes of the impact of filamentary environment because their local environment can be determined more accurately. We use the Bisous marked point process method to detect cosmic-web filaments with radii of $0.5-1.0$ Mpc and measure the perpendicular filament spine distance ($D_{\mathrm{fil}}$) for the BGGs. We limit our study to $D_{\mathrm{fil}}$ values up to 4 Mpc. We use the luminosity density field as a tracer of the local environment. To achieve uniformity of the sample and to reduce potential biases we only consider filaments longer than 5 Mpc. Our final sample contains 1427 BGGs. Results. We note slight deviations between the galaxy populations inside and outside the filament radius in terms of stellar mass, colour, the 4000AA break, specific star formation rates, and morphologies. However, all these differences remain below 95% confidence and are negligible compared to the effects arising from local environment density. Conclusions. Within a 4 Mpc radius of the filament axes, the effect of filaments on BGGs is marginal. The local environment is the main factor in determining BGG properties.

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arXiv2017

Galaxy evolution in merging clusters: The passive core of the "Train Wreck" cluster of galaxies, A520

The mergers of galaxy clusters are the most energetic events in the universe after the Big Bang. With the increased availability of multi-object spectroscopy and X-ray data an ever increasing fraction of local clusters are recognised as exhibiting signs of recent or past merging events on various scales. Our goal is to probe how these mergers affect the evolution and content of their member galaxies. We specifically aim to answer the following questions: Is the quenching of star formation in merging clusters enhanced when compared with relaxed clusters? Is the quenching preceded by a (short lived) burst of star formation? We obtained optical spectroscopy of >400 galaxies in the field of the merging cluster Abell 520. We combine these observations with archival data to get a comprehensive picture of the state of star formation in the members of this merging cluster. Finally, we compare these observations with a control sample of 10 non-merging clusters at the same redshift from The Arizona Cluster Redshift Survey (ACReS). We split the member galaxies in passive, star forming or recently quenched depending on their spectra. The core of the merger shows a decreased fraction of star forming galaxies compared to clusters in the non-merging sample. This region, dominated by passive galaxies, is extended along the axis of the merger. We find evidence of rapid quenching of the galaxies during the core passage with no signs of a star burst on the time scales of the merger (~0.4Gyr). Additionally, we report the tentative discovery of an infalling group along the main filament feeding the merger, currently at ~2.5 Mpc from the merger centre. This group contains a high fraction of star forming galaxies as well as ~2/3 of all the recently quenched galaxies in our survey.

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arXiv2017

From voids to filaments: environmental transformations of galaxies in the SDSS

We investigate the impact of filament and void environments on galaxies, looking for residual effects beyond the known relations with environment density. We quantified the host environment of galaxies as the distance to the spine of the nearest filament, and compared various galaxy properties within 12 bins of this distance. We considered galaxies up to 10 $h^{-1}$Mpc from filaments, i.e. deep inside voids. The filaments were defined by a point process (the Bisous model) from the Sloan Digital Sky Survey data release 10. In order to remove the dependence of galaxy properties on the environment density and redshift, we applied weighting to normalise the corresponding distributions of galaxy populations in each bin. After the normalisation with respect to environment density and redshift, several residual dependencies of galaxy properties still remain. Most notable is the trend of morphology transformations, resulting in a higher elliptical-to-spiral ratio while moving from voids towards filament spines, bringing along a corresponding increase in the $g-i$ colour index and a decrease in star formation rate. After separating elliptical and spiral subsamples, some of the colour index and star formation rate evolution still remains. The mentioned trends are characteristic only for galaxies brighter than about $M_{r} = -20$ mag. Unlike some other recent studies, we do not witness an increase in the galaxy stellar mass while approaching filaments. The detected transformations can be explained by an increase in the galaxy-galaxy merger rate and/or the cut-off of extragalactic gas supplies (starvation) near and inside filaments. Unlike voids, large-scale galaxy filaments are not a mere density enhancement, but have their own specific impact on the constituent galaxies, reducing the star formation rate and raising the chances of elliptical morphology also at a fixed environment density level.

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arXiv2017

Spiral arms and disc stability in the Andromeda galaxy

Aims: Density waves are often considered as the triggering mechanism of star formation in spiral galaxies. Our aim is to study relations between different star formation tracers (stellar UV and near-IR radiation and emission from HI, CO and cold dust) in the spiral arms of M31, to calculate stability conditions in the galaxy disc and to draw conclusions about possible star formation triggering mechanisms. Methods: We select fourteen spiral arm segments from the de-projected data maps and compare emission distributions along the cross sections of the segments in different datasets to each other, in order to detect spatial offsets between young stellar populations and the star forming medium. By using the disc stability condition as a function of perturbation wavelength and distance from the galaxy centre we calculate the effective disc stability parameters and the least stable wavelengths at different distances. For this we utilise a mass distribution model of M31 with four disc components (old and young stellar discs, cold and warm gaseous discs) embedded within the external potential of the bulge, the stellar halo and the dark matter halo. Each component is considered to have a realistic finite thickness. Results: No systematic offsets between the observed UV and CO/far-IR emission across the spiral segments are detected. The calculated effective stability parameter has a minimal value Q_{eff} ~ 1.8 at galactocentric distances 12 - 13 kpc. The least stable wavelengths are rather long, with the minimal values starting from ~ 3 kpc at distances R > 11 kpc. Conclusions: The classical density wave theory is not a realistic explanation for the spiral structure of M31. Instead, external causes should be considered, e.g. interactions with massive gas clouds or dwarf companions of M31.

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arXiv2016

Stellar kinematics using a third integral of motion: method and application on the Andromeda galaxy

We probe the feasibility of describing the structure of a multi-component axisymmetric galaxy with a dynamical model based on the Jeans equations while taking into account a third integral of motion. We demonstrate that using the third integral in the form derived by G. Kuzmin, it is possible to calculate the stellar kinematics of a galaxy from the Jeans equations by integrating the equations along certain characteristic curves. In cases where the third integral of motion does not describe the system exactly, the derived kinematics would describe the galaxy only approximately. We apply our method to the Andromeda galaxy, for which the mass distribution is relatively firmly known. We are able to reproduce the observed stellar kinematics of the galaxy rather well. The calculated model suggests that the velocity dispersion ratios $σ_z^2/σ_R^2$ of M31 decrease with increasing R. Moving away from the galactic plane, $σ_z^2/σ_R^2$ remains the same. The velocity dispersions $σ_θ^2$ and $σ_R^2$ are roughly equal in the galactic plane.

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arXiv2015

Galaxy pairs align with galactic filaments

Context. Gravitational collapse theory and numerical simulations suggest that the velocity field within large-scale galaxy filaments is dominated by motions along the filaments. Aims. Our aim is to check whether observational data reveal any preferred orientation of galaxy pairs with respect to the underlying filaments as a result of the expectedly anisotropic velocity field. Methods. We use galaxy pairs and galaxy filaments identified from the Sloan Digital Sky Survey data. For filament extraction, we use the Bisous model that is based the marked point process technique. During the filament detection, we use the centre point of each pair instead of the positions of galaxies to avoid a built-in influence of pair orientation on the filament construction. For pairs lying within filaments (3012 cases), we calculate the angle between the line connecting galaxies of each pair and their host filament. To avoid redshift-space distortions, the angle is measured in the plain of the sky. Results. The alignment analysis shows that the orientation of galaxy pairs correlates strongly with their host filaments. The alignment signal is stronger for loose pairs, with at least 25% excess of aligned pairs compared to a random distribution. The alignment of galaxy pairs and filaments measured from the observational data is in good concordance with the alignment in the Millennium simulation and thus provides support to the ΛCDM formalism.

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arXiv2010

SDSS surface photometry of M 31 with absorption corrections

The objective of this work is to obtain an extinction-corrected distribution of optical surface brightness and colour indices of the large nearby galaxy M 31 using homogeneous observational data and a model for intrinsic extinction. We process the Sloan Digital Sky Survey (SDSS) images in ugriz passbands and construct corresponding mosaic images, taking special care of subtracting the varying sky background. We apply the galactic model developed in Tempel et al. (2010) and far-infrared imaging to correct the photometry for intrinsic dust effects. We obtain observed and dust-corrected distributions of the surface brightness of M 31 and a map of line-of-sight extinctions inside the galaxy. Our extinction model suggests that either M 31 is intrinsically non-symmetric along the minor axis or the dust properties differ from those of the Milky Way. Assuming the latter case, we present the surface brightness distributions and integral photometry for the Sloan filters as well as the standard UBVRI system. We find the following intrinsic integral colour indices for M 31: (U-B)_0=0.35; (B-V)_0=0.86; (V-R)_0=0.63; (R-I)_0=0.53; the total intrinsic absorption-corrected luminosities of M 31 in the B and the V filters are 4.10 and 3.24 mag, respectively.

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arXiv2009

Dust-corrected surface photometry of M 31 from the Spitzer far infrared observations

We create a model for recovering the intrinsic, absorption-corrected surface brightness distribution of a galaxy and apply the model to the M31. We construct a galactic model as a superposition of axially symmetric stellar components and a dust disc to analyse the intrinsic absorption efects. Dust column density is assumed to be proportional to the far-infrared flux of the galaxy. Along each line of sight, the observed far-infrared spectral energy distribution is approximated with modified black body functions considering dust components with different temperatures, allowing to determine the temperatures and relative column densities of the dust components. We apply the model to the nearby galaxy M31 using the Spitzer Space Telescope far-infrared observations for mapping dust distribution and temperature. A warm and a cold dust component are distinguished. The temperature of the warm dust in M31 varies between 56 and 60 K and is highest in the spiral arms; the temperature of the cold component is mostly 15-19 K and rises up to about 25 K at the centre of the galaxy. The intensity-weighted mean temperature of the dust decreases from T ~32 K at the centre to T ~20 K at R ~7 kpc and outwards. We also calculate the intrinsic UBVRIL surface brightness distributions and the spatial luminosity distribution. The intrinsic dust extinction in the V-colour rises from 0.25 mag at the centre to 0.4-0.5 mag at R = 6-13 kpc and decreases smoothly thereafter. The calculated total extinction-corrected luminosity of M31 is L_B = (3.64 pm 0.15) 10^10L_sun, corresponding to an absolute luminosity M_B = (-20.89 pm 0.04) mag. Of the total B-luminosity, 20% (0.24 mag) is obscured from us by the dust inside M31. The intrinsic shape of the bulge is slightly prolate in our best-fit model.

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arXiv2008

Where have all the bulges gone?

Several recent studies indicate that bulges are more complex than merely structureless relaxed stellar systems. We study the HST images of a sample of 130 nearby early type (S0-Sab) disc galaxies and detect pure structureless bulges with the Sersic index n > 2 for only 12% of the galaxies. Other galaxies show varied substructure in their inner regions (inner bars, inner spiral arms, inner rings) and sometimes contain no bulge at all. Inner substructure is more common for these galaxies, which also display structure at larger scales.

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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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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

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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