Martin Sahlén
A5049029223- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Scientific Research and Discoveries
- Adaptive optics and wavefront sensing
- Superconducting and THz Device Technology
- Relativity and Gravitational Theory
- History and Developments in Astronomy
- Gaussian Processes and Bayesian Inference
- Calibration and Measurement Techniques
- Advanced Physical and Chemical Molecular Interactions
- Remote Sensing in Agriculture
- Geophysics and Gravity Measurements
- Advanced optical system design
- Statistical and numerical algorithms
- Spectroscopy and Chemometric Analyses
- Philosophy and History of Science
- Impact of Light on Environment and Health
Uppsala University
2017-2025
Universidade Estadual de Campinas (UNICAMP)
2022-2024
Institut d'Astrophysique Spatiale
2024
Swedish Collegium for Advanced Study
2021-2022
University of Oxford
2013-2020
Campbell Collaboration
2019
Johns Hopkins University
2018
Ulverscroft (United Kingdom)
2016
Stockholm University
2005-2013
AlbaNova
2005-2012
Abstract We present a detailed overview of the cosmological surveys that we aim to carry out with Phase 1 Square Kilometre Array (SKA1) and science they will enable. highlight three main surveys: medium-deep continuum weak lensing low-redshift spectroscopic HI galaxy survey over 5 000 deg 2 ; wide deep intensity mapping (IM) 20 from $z = 0.35$ 3; deep, high-redshift IM 100 3$ 6. Taken together, these achieve an array important scientific goals: measuring equation state dark energy \sim...
ABSTRACT We describe updates to the redMaPPer algorithm, a photometric red-sequence cluster finder specifically designed for large surveys. The updated algorithm is applied of Science Verification (SV) data from Dark Energy Survey (DES), and Sloan Digital Sky (SDSS) DR8 set. DES SV catalog locally volume limited contains 786 clusters with richness (roughly equivalent ) . consists 26,311 , sharply increasing threshold as function redshift performance both catalogs shown be excellent,...
The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMM–Newton Science Archive. Its main aims are to measure cosmological parameters and trace evolution of X-ray scaling relations. In this paper we present first release from (XCS-DR1). This consists 503 optically confirmed, serendipitously detected, clusters. Of these clusters, 256 new literature 357 discoveries. We 463 with redshift estimate (0.06 < z 1.46), including 261...
Abstract The Square Kilometre Array (SKA) is a planned large radio interferometer designed to operate over wide range of frequencies, and with an order magnitude greater sensitivity survey speed than any current telescope. SKA will address many important topics in astronomy, ranging from planet formation distant galaxies. However, this work, we consider the perspective as facility for studying physics. We review four areas which expected make major contributions our understanding fundamental...
We use Chandra X-ray and Spitzer infrared observations to explore the AGN starburst populations of XMMXCS J2215.9-1738 at z=1.46, one most distant spectroscopically confirmed galaxy clusters known. The high resolution imaging reveals that cluster emission is contaminated by point sources were not resolved in XMM system, have effect hardening spectrum, leading previously reported temperature for this system being overestimated. From a joint spectroscopic analysis data, found T=4.1_-0.9^+0.6...
We present deep J and K s band photometry of 20 high redshift galaxy clusters between z = 0.8-1.5, 19 which are observed with the MOIRCS instrument on Subaru Telescope.By using nearinfrared light as a proxy for stellar mass we find surprising result that average Brightest Cluster Galaxies (BCGs) has remained constant at ∼ 9 × 10 11 M ⊙ since 1.5.We investigate effect this differing star formation histories generated by three well known independent population codes it to be robust reasonable,...
The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate fifth force. If it exists, this force would influence hot X-ray emitting gas filling potential wells galaxy clusters. However, not clusters weak lensing signal. Therefore, by comparing and profiles, one can place upper limits on strength This technique has been attempted before using single, nearby cluster (Coma, z = 0.02). Here we apply stacked profiles 58 at higher redshifts (0.1 <...
The center determination of a galaxy cluster from an optical finding algorithm can be offset theoretical prescriptions or $N$-body definitions its host halo center. These offsets impact the recovered statistics, affecting both richness measurements and weak lensing shear profile around clusters. This paper models centering performance \RM~cluster using archival X-ray observations \RM-selected Assuming emission peaks as fiducial centers, through analyzing their to \RM~centers, we find that...
The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMM-Newton Science Archive. Its main aims are to measure cosmological parameters and trace evolution of X-ray scaling relations. In this paper we describe processing methodology applied 5,776 observations used construct current XCS source catalogue. A total 3,675 > 4-sigma cluster candidates with 50 background-subtracted counts extracted from non-overlapping area suitable...
Using a sample of 123 X-ray clusters and groups drawn from the XMM-Cluster Survey first data release, we investigate interplay between brightest cluster galaxy (BCG), its black hole, intra-cluster/group medium (ICM). It appears that for with BCG likely to host significant AGN feedback, gas cooling dominates in those Tx > 2 keV while feedback below. This may be understood through sub-unity exponent found scaling relation derive mass over halo range 10^13 < M500 10^15Msol lack correlation...
This paper presents both the result of a search for fossil systems (FSs) within XMM Cluster Survey and Sloan Digital Sky results study stellar mass assembly populations their galaxies. In total, 17 groups clusters are identified at z < 0.25 with large magnitude gaps between first fourth brightest All information necessary to classify these as fossils is provided. For clusters, total fractional luminosity galaxy positively correlated gap. The galaxies in FSs (called galaxies) have star...
Using the science verification data of Dark Energy Survey (DES) for a new sample 106 X-Ray selected clusters and groups, we study stellar mass growth Bright Central Galaxies (BCGs) since redshift 1.2. Compared with expectation in semi-analytical model applied to Millennium Simulation, observed BCGs become under-massive/under-luminous decreasing redshift. We incorporate uncertainties associated cluster mass, redshift, BCG measurements into analysis redshift-dependent BCG-cluster relation,...
Cosmic voids, the less dense patches of Universe, are promising laboratories to extract cosmological information. Thanks their unique low density character, voids extremely sensitive diffuse components such as neutrinos and dark energy, represent ideal environments study modifications gravity, where effects expected be more prominent. Robust void-related observables, including for example redshift-space distortions (RSD) weak lensing around a way chase test new physics. Cosmological analysis...
Astroparticle physics is undergoing a profound transformation, due to series of extraordinary new results, such as the discovery high-energy cosmic neutrinos with IceCube, direct detection gravitational waves LIGO and Virgo, many others. This white paper result collaborative effort that involved hundreds theoretical astroparticle physicists cosmologists, under coordination European Consortium for Theory (EuCAPT). Addressed whole community, it explores upcoming opportunities challenges our...
Euclid is poised to survey galaxies across a cosmological volume of unprecedented size, providing observations more than billion objects distributed over third the full sky. Approximately 20 million these will have their spectroscopy available, allowing us map 3D large-scale structure Universe in great detail. This paper investigates prospects for detection cosmic voids therein and unique benefit they provide cosmology. In particular, we study imprints dynamic geometric distortions average...
The Euclid mission $-$ with its spectroscopic galaxy survey covering a sky area over $15\,000 \ \mathrm{deg}^2$ in the redshift range $0.9<z<1.8\ -$ will provide sample of tens thousands cosmic voids. This paper explores for first time constraining power void size function on properties dark energy (DE) from mock catalogue, official Flagship simulation. We identify voids light-cone, which closely matches features upcoming data set. model considering state-of-the art methodology: we rely...
Abstract We describe features of the X-ray: Generate and Analyse (Xga) open-source software package that have been developed to facilitate automated hydrostatic mass (Mhydro) measurements from XMM X-ray observations clusters galaxies. This includes describing how Xga measures global, radial, properties galaxy clusters. then demonstrate reliability by comparing simple properties, namely temperature gas mass, with published values presented Cluster Survey (XCS), Ultimate eXtragaLactic survey...
We describe an algorithm which directly determines the quintessence potential from observational data, without using equation of state parametrization. The strategy is to numerically determine quantities as a function expansion coefficients potential, are then constrained likelihood approach. further impose model selection criterion, Bayesian Information Criterion, appropriate level expansion. In addition parameters, present day field velocity kept free parameter. Our investigation contains...
We present a study of the morphological fractions and color–magnitude relation (CMR) in most distant X-ray selected galaxy cluster currently known, XMMXCS J2215.9 − 1738 at z = 1.46, using combination optical imaging data obtained with Hubble Space Telescope Advanced Camera for Surveys, infrared from Multi-Object Infrared Spectrograph, mounted on 8.2 m Subaru telescope. find that mix population is similar to clusters ∼ 1. Within central 0.5 Mpc, approximately ∼62% galaxies identified as...
Modified gravity has garnered interest as a backstop against dark matter and energy (DE). As one possible modification, the graviton can become massive, which introduces new scalar field--here with Galileon-type symmetry. The field lead to nontrivial equation of state DE is density scale dependent. Tension between type Ia supernovae Planck could be reduced. In voids, dramatically alters DE, induces soon-observable gravitational slip two metric potentials, develops topological defect (domain...
Combining galaxy cluster and void abundances breaks the degeneracy between mean matter density $\Omega_{\rm m}$ power spectrum normalization $\sigma_8$. In a first for voids, we constrain m} = 0.21 \pm 0.10$ $\sigma_8 0.95 0.21$ flat $\Lambda$CDM universe, using extreme-value statistics on claimed largest void. The Planck-consistent results detect dark energy with two objects, independently of other probes. Cluster-void studies also offer complementarity in scale, density, non-linearity -...
Abstract We introduce a galaxy cluster mass observable, μ⋆, based on the stellar masses of members, and we present results for Dark Energy Survey (DES) Year 1 (Y1) observations. Stellar are computed using Bayesian model averaging method, validated DES data simulations COSMOS data. show that μ⋆ works as promising proxy by comparing our predictions to X-ray measurements. measure temperature–μ⋆ relation total 129 clusters matched between wide-field Y1 redMaPPer catalogue Chandra XMM archival...
ABSTRACT Dark matter haloes that reach the H i-cooling mass without prior star formation or external metal pollution represent potential sites for of small – extremely faint Population III galaxies at high redshifts. Gravitational lensing may in rare cases boost their fluxes to detectable levels, but find even a number such objects randomly selected regions sky requires very large areas be surveyed. Because this, small, wide-field telescope can principle offer better detection prospects than...
We update and extend our previous work reconstructing the potential of a quintessence field from current observational data. cosmological data set to include new supernova data, plus information cosmic microwave background baryon acoustic oscillations. modeling by considering Pad\'e approximant expansions as well Taylor series, using observations assess viability tracker hypothesis. find that parameter constraints have improved factor 2, with strengthening preference constant over evolving...