arXiv subjects

A. Tamm

Publications and source records attributed to A. Tamm.

At least 19 recordsLinked to original sources

arXiv2026

J-PAS & FLAMINGO: Cosmic voids and void galaxies in the gravitational landscape of photometric surveys

Photometric surveys offer a powerful way to map the large-scale structure of the Universe, but their redshift errors complicate the identification of cosmic voids, challenging studies of their environmental effect on galaxy properties. We present an approach to robustly identify dynamically relevant voids and void galaxies in galaxy mocks of the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS), testing whether known trends in void galaxy properties survive photometric redshift errors. Using FLAMINGO mocks at z = 0.3 and mi < 20, we compare a FLAMINGO-based ideal (FBI) mock to a FLAMINGO-based JP mock with J-PAS-like redshift errors. We mitigate redshift errors using a quasi-gravitational potential field in the two galaxy mocks. We apply a watershed algorithm to the thresholded quasi-potential field to identify dynamically dominant voids, and define massive void galaxies alongside a comparison sample in high-density regions. Photometric errors lead to a slightly lower void abundance and a marginal shift toward larger, less spherical voids, but overall size and ellipticity distributions agree well between mocks. Their main impact is contamination of void interiors in the JP density profiles by galaxies scattered from high-density regions. We recover a reasonable number of FBI sample voids in the JP sample, with excellent size and shape agreement, occupying ~63% of the thresholded quasi-potential volume. In both mocks, void galaxies show lower stellar masses, bluer colours, and enhanced star formation relative to equal-mass galaxies in high-density regions. These results suggest a quasi-potential can mitigate redshift errors at the level expected for J-PAS, enabling identification of reliable, dynamically dominant voids that are less sensitive to small-scale noise. The massive void galaxy population shows the expected trends relative to high-density environments.

astro-ph.CO↗

arXiv2025

TOPz: Photometric redshifts using template fitting applied to the GAMA survey

Context. Accurate photometric redshift estimation is crucial for cosmological and galaxy evolution studies, especially with the advent of large-scale photometric surveys. Aims. We developed a photo-z estimation code called TOPz (Tartu Observatory Photo-z) and applied it to the GAMA photometric catalogue. Using nine-band photometric data from the GAMA project, we assessed the accuracy of TOPz by comparing its photo-z estimates to available spectroscopic redshifts from GAMA and DESI. The latter extends to z < 2 and m_Z < 24, allowing the photo-z accuracy to be validated beyond the GAMA limits. Methods. TOPz employs a Bayesian template-fitting approach to estimate photo-z from marginalised redshift posteriors. We generated synthetic galaxy spectra using the CIGALE software and ran template set optimisation. We improved the photometry by applying flux and flux uncertainty corrections. An analytical prior was then imposed on the resulting posteriors to refine the redshift estimates. Results. The photo-z estimates produced by TOPz show good agreement with the spectroscopic redshifts in the low-redshift regime (z < 0.5). We demonstrate the redshift accuracy across various magnitude bins and tested how the flux corrections and posteriors reflect the actual uncertainty of the estimates. For the GAMA sample, the sigma_NMAD = 0.012 for m_Z <18 and increases to sigma_NMAD = 0.021 for m_Z >19. The outlier fraction (|dz|/(1 + z)>0.1) in the same magnitude bins increases from 1% to 5%. We show that the TOPz results are consistent with those obtained from other photo-z codes (EAZY and SFM) applied to the same data set. Conclusions. TOPz is an advanced photo-z estimation code that integrates flux corrections, physical priors, and template set optimisation to provide state-of-the-art photo-z among competing template-based redshift estimators.

astro-ph.CO↗

arXiv2025

The J-PAS survey: The effect of photometric redshift errors on cosmic voids

We investigated the impact of photometric redshift errors in the ongoing Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS) on void identification and properties using a watershed-based method, aiming to assess the recovery of individual voids and the overall void environment. We created galaxy mock catalogues for redshift z = 0.1 using the IllustrisTNG300-1 simulation, defining two datasets: an $ideal$ sample ($m_r < 21$ mag) and a $perturbed$ sample with the Z-coordinate errors mimicking J-PAS's line-of-sight errors, derived from the precursor miniJPAS survey data. We identified voids using ZOBOV, a watershed algorithm. We found 1065 voids in the $ideal$ sample and 2558 voids in the $perturbed$ sample. The $perturbed$ sample voids have, on average, smaller sizes and denser interiors. We filtered out voids based on density and radius in order to eliminate overdense and small spurious instances. The stacked density profile of filtered voids in the $perturbed$ sample remains close to the average density even at the boundary peak, indicating a strong blurring of structures by the redshift errors. The number of $ideal$ sample voids for which at least $50\%$ of the volume is recovered by a void in the $perturbed$ sample is 53 (29 for the filtered sample). The volume occupied by these voids is less than $10\%$ of the simulation volume. Merging voids in the $perturbed$ sample marginally improves the recovery. The overall volumes defined as voids in the two samples have an overlap of $80\%$, making up $61\%$ of the simulation box volume. While some statistical properties of voids might be recovered sufficiently well, the watershed algorithms may not be optimal for recovering the large-scale structure voids if applied straight to photometric redshift survey data.

astro-ph.CO↗

arXiv2022

TOPz: Photometric redshifts for J-PAS

The importance of photometric galaxy redshift estimation is rapidly increasing with the development of specialised powerful observational facilities. We develop a new photometric redshift estimation workflow TOPz to provide reliable and efficient redshift estimations for the upcoming large-scale survey J-PAS which will observe 8500 deg2 of the northern sky through 54 narrow-band filters. TOPz relies on template-based photo-z estimation with some added J-PAS specific features and possibilities. We present TOPz performance on data from the miniJPAS survey, a precursor to the J-PAS survey with an identical filter system. First, we generated spectral templates based on the miniJPAS sources using the synthetic galaxy spectrum generation software CIGALE. Then we applied corrections to the input photometry by minimising systematic offsets from the template flux in each filter. To assess the accuracy of the redshift estimation, we used spectroscopic redshifts from the DEEP2, DEEP3, and SDSS surveys, available for 1989 miniJPAS galaxies with r < 22 magAB. We also tested how the choice and number of input templates, photo-z priors, and photometric corrections affect the TOPz redshift accuracy. The general performance of the combination of miniJPAS data and the TOPz workflow fulfills the expectations for J-PAS redshift accuracy. Similarly to previous estimates, we find that 38.6% of galaxies with r < 22 mag reach the J-PAS redshift accuracy goal of dz/(1 + z) < 0.003. Limiting the number of spectra in the template set improves the redshift accuracy up to 5%, especially for fainter, noise-dominated sources. Further improvements will be possible once the actual J-PAS data become available.

astro-ph.IM↗

arXiv2021

The miniJPAS survey: the photometric redshift catalogue

MiniJPAS is a ~1 deg^2 imaging survey of the AEGIS field in 60 bands, performed to demonstrate the scientific potential of the upcoming JPAS survey. Full coverage of the 3800-9100 Årange with 54 narrow and 6 broad optical filters allow for extremely accurate photo-z, which applied over 1000s of deg^2 will enable new applications of the photo-z technique such as measurement of baryonic acoustic oscillations. In this paper we describe the method used to obtain the photo-z included in the publicly available miniJPAS catalogue, and characterise the photo-z performance. We build 100 Åresolution photo-spectra from the PSF-corrected forced-aperture photometry. Systematic offsets in the photometry are corrected by applying magnitude shifts obtained through iterative fitting with stellar population synthesis models. We compute photo-z with a customised version of LePhare, using a set of templates optimised for the J-PAS filter-set. We analyse the accuracy of miniJPAS photo-z and their dependence on multiple quantities using a subsample of 5,266 galaxies with spectroscopic redshifts from SDSS and DEEP, that we find to be representative of the whole r<23 miniJPAS sample. Formal uncertainties for the photo-z that are calculated with the δχ^2 method underestimate the actual redshift errors. The odds parameter has the stronger correlation with |Dz|, and accurately reproduces the probability of a redshift outlier (|Dz|>0.03) irrespective of the magnitude, redshift, or spectral type of the sources. We show that the two main summary statistics characterising the photo-z accuracy for a population of galaxies (snmad and η) can be predicted by the distribution of odds in such population, and use this to estimate them for the whole miniJPAS sample. At r<23 there are 17,500 galaxies/deg^2 with valid photo-z estimates, of which 4,200 are expected to have |Dz|<0.003 (abridged).

astro-ph.GA↗

arXiv2020

The miniJPAS survey: a preview of the Universe in 56 colours

The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will soon start to scan thousands of square degrees of the northern extragalactic sky with a unique set of $56$ optical filters from a dedicated $2.55$m telescope, JST, at the Javalambre Astrophysical Observatory. Before the arrival of the final instrument (a 1.2 Gpixels, 4.2deg$^2$ field-of-view camera), the JST was equipped with an interim camera (JPAS-Pathfinder), composed of one CCD with a 0.3deg$^2$ field-of-view and resolution of 0.23 arcsec pixel$^{-1}$. To demonstrate the scientific potential of J-PAS, with the JPAS-Pathfinder camera we carried out a survey on the AEGIS field (along the Extended Groth Strip), dubbed miniJPAS. We observed a total of $\sim 1$ deg$^2$, with the $56$ J-PAS filters, which include $54$ narrow band (NB, $\rm{FWHM} \sim 145$Angstrom) and two broader filters extending to the UV and the near-infrared, complemented by the $u,g,r,i$ SDSS broad band (BB) filters. In this paper we present the miniJPAS data set, the details of the catalogues and data access, and illustrate the scientific potential of our multi-band data. The data surpass the target depths originally planned for J-PAS, reaching $\rm{mag}_{\rm {AB}}$ between $\sim 22$ and $23.5$ for the NB filters and up to $24$ for the BB filters ($5σ$ in a $3$~arcsec aperture). The miniJPAS primary catalogue contains more than $64,000$ sources extracted in the $r$ detection band with forced photometry in all other bands. We estimate the catalogue to be complete up to $r=23.6$ for point-like sources and up to $r=22.7$ for extended sources. Photometric redshifts reach subpercent precision for all sources up to $r=22.5$, and a precision of $\sim 0.3$% for about half of the sample. (Abridged)

astro-ph.CO↗

arXiv2018

Langevin dynamics with spatial correlations as a model for electron-phonon coupling

Stochastic Langevin dynamics has been traditionally used as a tool to describe non-equilibrium processes. When utilized in systems with collective modes, traditional Langevin dynamics relaxes all modes indiscriminately, regardless of their wavelength. We propose a generalization of Langevin dynamics that can capture a differential coupling between collective modes and the bath, by introducing spatial correlations in the random forces. This allows modeling the electronic subsystem in a metal as a generalized Langevin bath endowed with a concept of locality, greatly improving the capabilities of the two-temperature model. The specific form proposed here for the spatial correlations produces physical wavevector- and polarization-dependency of the relaxation produced by the electron-phonon coupling in a solid. We show that the resulting model can be used for describing the path to equilibration of ions and electrons, and also as a thermostat to sample the equilibrium canonical ensemble. By extension, the family of models presented here can be applied in general to any dense system, solids, alloys and dense plasmas. As an example, we apply the model to study the non-equilibrium dynamics of an electron-ion two-temperature Ni crystal.

cond-mat.stat-mech↗

arXiv2018

J-PLUS: The Javalambre Photometric Local Universe Survey

J-PLUS is an ongoing 12-band photometric optical survey, observing thousands of square degrees of the Northern hemisphere from the dedicated JAST/T80 telescope at the Observatorio Astrofísico de Javalambre. T80Cam is a 2 sq.deg field-of-view camera mounted on this 83cm-diameter telescope, and is equipped with a unique system of filters spanning the entire optical range. This filter system is a combination of broad, medium and narrow-band filters, optimally designed to extract the rest-frame spectral features (the 3700-4000Å Balmer break region, H$δ$, Ca H+K, the G-band, the Mgb and Ca triplets) that are key to both characterize stellar types and to deliver a low-resolution photo-spectrum for each pixel of the sky observed. With a typical depth of AB $\sim 21.25$ mag per band, this filter set thus allows for an indiscriminate and accurate characterization of the stellar population in our Galaxy, it provides an unprecedented 2D photo-spectral information for all resolved galaxies in the local universe, as well as accurate photo-z estimates ($Δ\,z\sim 0.01-0.03$) for moderately bright (up to $r\sim 20$ mag) extragalactic sources. While some narrow band filters are designed for the study of particular emission features ([OII]/$λ$3727, H$α$/$λ$6563) up to $z < 0.015$, they also provide well-defined windows for the analysis of other emission lines at higher redshifts. As a result, J-PLUS has the potential to contribute to a wide range of fields in Astrophysics, both in the nearby universe (Milky Way, 2D IFU-like studies, stellar populations of nearby and moderate redshift galaxies, clusters of galaxies) and at high redshifts (ELGs at $z\approx 0.77, 2.2$ and $4.4$, QSOs, etc). With this paper, we release $\sim 36$ sq.deg of J-PLUS data, containing about $1.5\times 10^5$ stars and $10^5$ galaxies at $r<21$ mag.

astro-ph.GA↗

arXiv2016

Alignment of galaxies relative to their local environment in SDSS-DR8

We study the alignment of galaxies relative to their local environment in SDSS-DR8 and, using these data, we discuss evolution scenarios for different types of galaxies. We defined a vector field of the direction of anisotropy of the local environment of galaxies. We summed the unit direction vectors of all close neighbours of a given galaxy in a particular way to estimate this field. We found the alignment angles between the spin axes of disc galaxies, or the minor axes of elliptical galaxies, and the direction of anisotropy. The distributions of cosines of these angles are compared to the random distributions to analyse the alignment of galaxies. Sab galaxies show perpendicular alignment relative to the direction of anisotropy in a sparse environment, for single galaxies and galaxies of low luminosity. Most of the parallel alignment of Scd galaxies comes from dense regions, from 2...3 member groups and from galaxies with low luminosity. The perpendicular alignment of S0 galaxies does not depend strongly on environmental density nor luminosity; it is detected for single and 2...3 member group galaxies, and for main galaxies of 4...10 member groups. The perpendicular alignment of elliptical galaxies is clearly detected for single galaxies and for members of < 11 member groups; the alignment increases with environmental density and luminosity. We confirm the existence of fossil tidally induced alignment of Sab galaxies at low z. The alignment of Scd galaxies can be explained via the infall of matter to filaments. S0 galaxies may have encountered relatively massive mergers along the direction of anisotropy. Major mergers along this direction can explain the alignment of elliptical galaxies. Less massive, but repeated mergers are possibly responsible for the formation of elliptical galaxies in sparser areas and for less luminous elliptical galaxies.

astro-ph.GA↗

arXiv2016

The Herschel Exploitation of Local Galaxy Andromeda (HELGA) VII: A SKIRT radiative transfer model and insights on dust heating

The radiation of stars heats dust grains in the diffuse interstellar medium and in star-forming regions in galaxies. Modelling this interaction provides information on dust in galaxies, a vital ingredient for their evolution. It is not straightforward to identify the stellar populations heating the dust, and to link attenuation to emission on a sub-galactic scale. Radiative transfer models are able to simulate this dust-starlight interaction in a realistic, three-dimensional setting. We investigate the dust heating mechanisms on a local and global galactic scale, using the Andromeda galaxy (M31) as our laboratory. We perform a series of panchromatic radiative transfer simulations of Andromeda with our code SKIRT. The high inclination angle of M31 complicates the 3D modelling and causes projection effects. However, the observed morphology and flux density are reproduced fairly well from UV to sub-millimeter wavelengths. Our model reveals a realistic attenuation curve, compatible with previous, observational estimates. We find that the dust in M31 is mainly (91 % of the absorbed luminosity) heated by the evolved stellar populations. The bright bulge produces a strong radiation field and induces non-local heating up to the main star-forming ring at 10 kpc. The relative contribution of unevolved stellar populations to the dust heating varies strongly with wavelength and with galactocentric distance.The dust heating fraction of unevolved stellar populations correlates strongly with NUV-r colour and specific star formation rate. These two related parameters are promising probes for the dust heating sources at a local scale.

astro-ph.GA↗

arXiv2016

Friends-of-friends galaxy group finder with membership refinement. Application to the local Universe

Context. Groups form the most abundant class of galaxy systems. They act as the principal drivers of galaxy evolution and can be used as tracers of the large-scale structure and the underlying cosmology. However, the detection of galaxy groups from galaxy redshift survey data is hampered by several observational limitations. Aims. We improve the widely used friends-of-friends (FoF) group finding algorithm with membership refinement procedures and apply the method to a combined dataset of galaxies in the local Universe. A major aim of the refinement is to detect subgroups within the FoF groups, enabling a more reliable suppression of the fingers-of-God effect. Methods. The FoF algorithm is often suspected of leaving subsystems of groups and clusters undetected. We used a galaxy sample built of the 2MRS, CF2, and 2M++ survey data comprising nearly 80000 galaxies within the local volume of 430 Mpc radius to detect FoF groups. We conducted a multimodality check on the detected groups in search for subgroups. We furthermore refined group membership using the group virial radius and escape velocity to expose unbound galaxies. We used the virial theorem to estimate group masses. Results. The analysis results in a catalogue of 6282 galaxy groups in the 2MRS sample with two or more members, together with their mass estimates. About half of the initial FoF groups with ten or more members were split into smaller systems with the multimodality check. An interesting comparison to our detected groups is provided by another group catalogue that is based on similar data but a completely different methodology. Two thirds of the groups are identical or very similar. Differences mostly concern the smallest and largest of these other groups, the former sometimes missing and the latter being divided into subsystems in our catalogue.

astro-ph.CO↗

arXiv2015

Recovering 3D structural properties of galaxies from SDSS-like photometry

Because of the 3D nature of galaxies, an algorithm for constructing spatial density distribution models of galaxies on the basis of galaxy images has many advantages over surface density distribution approximations. We present a method for deriving spatial structure and overall parameters of galaxies from images and estimate its accuracy and derived parameter degeneracies on a sample of idealised model galaxies. The test galaxies consist of a disc-like component and a spheroidal component with varying proportions and properties. Both components are assumed to be axially symmetric and coplanar. We simulate these test galaxies as if observed in the SDSS project through ugriz filters, thus gaining a set of realistically imperfect images of galaxies with known intrinsic properties. These artificial SDSS galaxies were thereafter remodelled by approximating the surface brightness distribution with a 2D projection of a bulge+disc spatial distribution model and the restored parameters were compared to the initial ones. Down to the r-band limiting magnitude 18, errors of the restored integral luminosities and colour indices remain within 0.05 mag and errors of the luminosities of individual components within 0.2 mag. Accuracy of the restored bulge-to-disc ratios (B/D) is within 40% in most cases, and becomes worse for galaxies with low B/D, but the general balance between bulges and discs is not shifted systematically. Assuming that the intrinsic disc axial ratio is < 0.3, the inclination angles can be estimated with errors < 5deg for most of the galaxies with B/D < 2 and with errors < 15deg up to B/D = 6. Errors of the recovered sizes of the galactic components are below 10% in most cases. In general, models of disc components are more accurate than models of spheroidal components for geometrical reasons.

astro-ph.CO↗

arXiv2015

Missing baryons traced by the galaxy luminosity density in the large-scale WHIM filaments

We propose a new approach to the missing baryons problem. Building on the common assumption that the missing baryons are in the form of the Warm Hot Intergalactic Medium (WHIM), we further assumed here that the galaxy luminosity density can be used as a tracer of the WHIM. The latter assumption is supported by our finding of a significant correlation between the WHIM density and the galaxy luminosity density in the hydrodynamical simulations of Cui et al. (2012). We further found that the fraction of the gas mass in the WHIM phase is substantially (by a factor of $\sim$1.6) higher within the large scale galactic filaments, i.e. $\sim$70\%, compared to the average in the full simulation volume of $\sim$0.1\,Gpc$^3$. The relation between the WHIM overdensity and the galaxy luminosity overdensity within the galactic filaments is consistent with linear: $δ_{\rm whim}\,=\,0.7\,\pm\,0.1\,\times\,δ_\mathrm{LD}^{0.9 \pm 0.2}$. We applied our procedure to the line of sight to the blazar H2356-309 and found evidence for the WHIM in correspondence of the Sculptor Wall (z $\sim$0.03 and $\log{N_H}$ = $19.9^{+0.1}_{-0.3}$) and Pisces-Cetus superclusters (z $\sim$0.06 and $\log{N_H}$ = $19.7^{+0.2}_{-0.3}$), in agreement with the redshifts and column densities of the X-ray absorbers identified and studied by Fang et al. (2010) and Zappacosta et al. (2010). This agreement indicates that the galaxy luminosity density and galactic filaments are reliable signposts for the WHIM and that our method is robust in estimating the WHIM density. The signal that we detected cannot originate from the halos of the nearby galaxies since they cannot account for the large WHIM column densities that our method and X-ray analysis consistently find in the Sculptor Wall and Pisces-Cetus superclusters.

astro-ph.CO↗

arXiv2014

The Herschel Exploitation of Local Galaxy Andromeda (HELGA): IV. Dust scaling relations at sub-kpc resolution

The imprints of dust-starlight interactions are visible in scaling relations between stellar characteristics, star formation parameters and dust properties. We aim to examine dust scaling relations on a sub-kpc resolution in the Andromeda galaxy (M31) by comparing the properties on a local and global scale to other galaxies of the local universe. New Herschel observations are combined with available data from GALEX, SDSS, WISE and Spitzer to construct a dataset covering UV to submm wavelengths. We work at the resolution of the SPIRE $500\; μ$m beam, with pixels corresponding to physical regions of 137 x 608 pc in the galaxy's disk. A panchromatic spectral energy distribution was modelled for each pixel and several dust scaling relations are investigated. We find, on a sub-kpc scale, strong correlations between $M_d/M_\star$ and NUV-r, and between $M_d/M_\star$ and $μ_\star$ (the stellar mass surface density). Striking similarities with corresponding relations based on integrated galaxies are found. We decompose M31 in four macro-regions based on their FIR morphology; the bulge, inner disk, star forming ring and the outer disk. All regions closely follow the galaxy-scale average trends. The specific star formation characteristics we derive for these macro-regions give strong hints of an inside-out formation of the bulge-disk geometry, as well as an internal downsizing process. However, within each macro-region, a great diversity in individual micro-regions is found. Furthermore, we confirm that dust in the bulge of M31 is heated only by the old stellar populations. In general, the local dust scaling relations indicate that the dust content in M31 is maintained by a subtle interplay of past and present star formation. The similarity with galaxy-based relations strongly suggests that they are in situ correlations, with underlying processes that must be local in nature. (Abriged)

astro-ph.GA↗

arXiv2014

Flux- and volume-limited groups/clusters for the SDSS galaxies: catalogues and mass estimation

We provide flux-limited and volume-limited galaxy group and cluster catalogues, based on the spectroscopic sample of the SDSS data release 10 galaxies. We used a modified friends-of-friends (FoF) method with a variable linking length in the transverse and radial directions to identify as many realistic groups as possible. The flux-limited catalogue incorporates galaxies down to m_r = 17.77 mag. It includes 588193 galaxies and 82458 groups. The volume-limited catalogues are complete for absolute magnitudes down to M_r = -18.0, -18.5, -19.0, -19.5, -20.0, -20.5, and -21.0; the completeness is achieved within different spatial volumes, respectively. Our analysis shows that flux-limited and volume-limited group samples are well compatible to each other, especially for the larger groups/clusters. Dynamical mass estimates, based on radial velocity dispersions and group extent in the sky, are added to the extracted groups. The catalogues can be accessed via http://cosmodb.to.ee and the Strasbourg Astronomical Data Center (CDS).

astro-ph.CO↗

arXiv2013

Orientation of cosmic web filaments with respect to the underlying velocity field

The large-scale structure of the Universe is characterised by a web-like structure made of voids, sheets, filaments, and knots. The structure of this so-called cosmic web is dictated by the local velocity shear tensor. In particular, the local direction of a filament should be strongly aligned with e3, the eigenvector associated with the smallest eigenvalue of the tensor. That conjecture is tested here on the basis of a cosmological simulation. The cosmic web delineated by the halo distribution is probed by a marked point process with interactions (the Bisous model), detecting filaments directly from the halo distribution (P-web). The detected P-web filaments are found to be strongly aligned with the local e3: the alignment is within 30 degree for 80% of the elements. This indicates that large-scale filaments defined purely from the distribution of haloes carry more than just morphological information, although the Bisous model does not make any prior assumption on the underlying shear tensor. The P-web filaments are also compared to the structure revealed from the velocity shear tensor itself (V-web). In the densest regions, the P- and V-web filaments overlap well (90%), whereas in lower density regions, the P-web filaments preferentially mark sheets in the V-web.

astro-ph.CO↗

arXiv2012

Modeling the Kinematics of Distant Galaxies

Evolution of galaxies is one of the most actual topics in astrophysics. Among the most important factors determining the evolution are two galactic components which are difficult or even impossible to detect optically: the gaseous disks and the dark matter halo. We use deep Hubble Space Telescope images to construct a two-component (bulge + disk) model for stellar matter distribution of galaxies. Properties of the galactic components are derived using a three-dimensional galaxy modeling software, which also estimates disk thickness and inclination angle. We add a gas disk and a dark matter halo and use hydrodynamical equations to calculate gas rotation and dispersion profiles in the resultant gravitational potential. We compare the kinematic profiles with the Team Keck Redshift Survey observations. In this pilot study, two galaxies are analyzed deriving parameters for their stellar components; both galaxies are found to be disk-dominated. Using the kinematical model, the gas mass and stellar mass ratio in the disk are estimated.

astro-ph.CO↗

arXiv2012

Stellar mass map and dark matter distribution in M31

Stellar mass distribution in M31 is estimated using optical and infrared imaging data. Combining the derived stellar mass model with various kinematical data, properties of the DM halo of the galaxy are constrained. SDSS observations through the ugriz filters and the Spitzer imaging at 3.6 microns are used to sample the SED of the galaxy at each imaging pixel. Intrinsic dust extinction effects are taken into account by using far-infrared observations. Synthetic SEDs created with different stellar population synthesis models are fitted to the observed SEDs, providing estimates for the stellar mass surface density. The stellar mass distribution of the galaxy is described with a 3D model consisting of a nucleus, a bulge, a disc, a young disc and a halo component, each following the Einasto density distribution (relations between different functional forms of the Einasto density distribution are given in App. B). By comparing the stellar mass distribution to the observed rotation curve and kinematics of outer globular clusters and satellite galaxies, the DM halo parameters are estimated. Stellar population synthesis models suggest that M31 is dominated by old stars throughout the galaxy. The total stellar mass is (10-15)10^10Msun, 30% of which is in the bulge and 56% in the disc. None of the tested DM distribution models can be falsified on the basis of the stellar matter distribution and the rotation curve of the galaxy. The virial mass of the DM halo is (0.8-1.1)10^12Msun and the virial radius is 189-213kpc, depending on the DM distribution. The central density of the DM halo is comparable to that of nearby dwarf galaxies, low-surface-brightness galaxies and distant massive disc galaxies, thus the evolution of central DM halo properties seems to be regulated by similar processes for a broad range of halo masses, environments, and cosmological epochs.

astro-ph.CO↗