Astronomical Observatory of the Jagiellonian University
(119951) 2002 KX14 is a large classical TNO with limited previous observations and unresolved questions regarding its physical properties. Five stellar occultations by 2002 KX14 were observed from 2020 to 2023, involving multiple telescopes across different locations in Europe and the Americas. The five occultations resulted in 15 positive chords, accurately measuring the 2002 KX14's shape and size. The projected ellipse has semi-major and semi-minor axes of 241.0±7.2241.0 \pm 7.2 km and 157.1±5.2157.1 \pm 5.2 km, respectively, corresponding to an average area-equivalent diameter of 389.2±8.7389.2 \pm 8.7 km. The geometric albedo was estimated at 11.9±0.7%11.9 \pm 0.7\%.
We present a study of optically-selected Type II AGN at 0.5 < z < 0.9 from the VIPERS and VVDS surveys, to investigate the connection between AGN activity and physical properties of their host galaxies. The host stellar mass is estimated through spectral energy distribution fitting with the CIGALE code, and star formation rates are derived from the [OII]λ\lambda3727 A˚Å line luminosity. We find that 49% of the AGN host galaxies are on or above the main sequence (MS), 40% lie in the sub-MS locus, and 11% in the quiescent locus. Using the [OIII]λ\lambda5007 A˚Å line luminosity as a proxy of the AGN power, we find that at fixed AGN power Type II AGN host galaxies show a bimodal behaviour: systems with host galaxy stellar mass <1010^{10} M_{\odot}, reside along the MS or in the starbursts locus (high-SF Type II AGN), while systems residing in massive host-galaxies (>1010^{10} M_{\odot}) show a lower level of star formation (low-SF Type II AGN). At all stellar masses, the offset from the MS is positively correlated with the AGN power. We interpret this correlation as evidence of co-evolution between the AGN and the host, possibly due to the availability of cold gas. In the most powerful AGN with host galaxies below the MS we find a hint, though weak, of asymmetry in the [OIII] line profile, likely due to outflowing gas, consistent with a scenario in which AGN feedback removes the available gas and halts the star formation in the most massive hosts.
Context. Magnetic fields are key to understand galaxy evolution, regulating stellar feedback and star formation in galaxies. Aims. We probe the origin of magnetic fields in late-type galaxies, measuring magnetic field strengths, exploring whether magnetic fields are only passive constituents of the interstellar medium, or whether they are active constituents being part of the local energy equilibrium. Methods. We measure equipartition magnetic field strengths in 39 galaxies from LoTSS-DR2 using LOFAR observations at 144 MHz with 6 arcsec angular resolution which (0.1-0.7 kpc). For a subset of 9 galaxies, we obtain atomic and molecular mass surface densities using HI and CO(2-1) data, from the THINGS and HERACLES surveys, respectively. These data are at 13 arcsec angular resolution, which corresponds to 0.3-1.2 kpc at the distances of our galaxies. We measure kinetic energy densities using HI and CO velocity dispersions. Results. We found a mean magnetic field strength of 3.6-12.5 μ\muG with a mean of 7.9±2.07.9 \pm 2.0 μ\muG across the full sample. The magnetic field strength has the tightest and steepest relation with the total gas surface density with BΣHI+H20.309±0.006B\propto \Sigma_{\rm HI+H2}^{0.309\pm0.006}. The relation with the star-formation rate surface density and molecular gas surface density has significantly flatter slopes. After accounting for the influence of cosmic-ray transport, we found an even steeper relation of BΣHI+H20.393±0.009B\propto \Sigma_{\rm HI+H2}^{0.393\pm0.009}. Conclusions. These results suggest that the magnetic field is regulated by a BB-ρ\rho relation, which has its origin in the saturation of the small-scale dynamo. This is borne out by an agreement of kinetic and magnetic energy densities although local deviations do exist in particular in areas of high kinetic energy densities where the magnetic field is sub-dominant.
We present multi-frequency and high-resolution studies of a sample of 24 radio transients sources discovered by comparing the NRAO VLA Sky Survey (NVSS) and Very Large Array Sky Survey (VLASS) surveys. All of them are characterized by a significant increase in radio flux density over the last two this http URL convex spectra, small sizes and high brightness temperatures are typical for young gigahertz-peaked spectrum (GPS) radio sources and indicative of an AGN buried in the host galaxy. On the other hand, they are much weaker than the archetypical GPS objects and their parsec-scale radio structures, although indicating the presence of young radio jets, are similar to radio-quiet AGNs like Seyfert and low-ionization nuclear emission-line region (LINER) galaxies. Based on the distribution of these objects in power-size (PDP - D) and peak frequency-size (νpD\nu_p - D) diagrams, we suggest that after stabilizing their radio activity, some of the GHz-peaked radio transients (galaxies and quasars) will develop into radio-intermediate and radio-quiet (RI/RQ) quasars and low-frequency peaked-spectrum (PS) objects. We discuss several possible origins for the transient radio emission in our sources and conclude that changes in the accretion rate combined with low-power radio ejecta are the most probable cause. This is the scenario we also propose for one of our sources, 101841-13, which was independently identified as a candidate tidal disruption event (TDE) based on its infrared variability. However, we cannot exclude that 101841-13 or other sources in our sample are TDEs.
We present a study of optically-selected Type II AGN at 0.5 < z < 0.9 from the VIPERS and VVDS surveys, to investigate the connection between AGN activity and physical properties of their host galaxies. The host stellar mass is estimated through spectral energy distribution fitting with the CIGALE code, and star formation rates are derived from the [OII]λ\lambda3727 A˚Å line luminosity. We find that 49% of the AGN host galaxies are on or above the main sequence (MS), 40% lie in the sub-MS locus, and 11% in the quiescent locus. Using the [OIII]λ\lambda5007 A˚Å line luminosity as a proxy of the AGN power, we find that at fixed AGN power Type II AGN host galaxies show a bimodal behaviour: systems with host galaxy stellar mass <1010^{10} M_{\odot}, reside along the MS or in the starbursts locus (high-SF Type II AGN), while systems residing in massive host-galaxies (>1010^{10} M_{\odot}) show a lower level of star formation (low-SF Type II AGN). At all stellar masses, the offset from the MS is positively correlated with the AGN power. We interpret this correlation as evidence of co-evolution between the AGN and the host, possibly due to the availability of cold gas. In the most powerful AGN with host galaxies below the MS we find a hint, though weak, of asymmetry in the [OIII] line profile, likely due to outflowing gas, consistent with a scenario in which AGN feedback removes the available gas and halts the star formation in the most massive hosts.
Linear time series analysis, mainly the Fourier transform based methods, has been quite successful in extracting information contained in the ever-modulating light curves (Lcs) of active galactic nuclei, and thereby contribute in characterizing the general features of supermassive black hole systems. In particular, the statistical properties of γ\gamma-ray variability of blazars are found to be fairly represented by flicker noise in the temporal frequency domain. However, these conventional methods have not been able to fully encapsulate the richness and the complexity displayed in the light curves of the sources. In this work, to complement our previous study on the similar topic, we perform non-linear time series analysis of the decade-long Fermi/LAT observations of 20 γ\gamma-ray bright blazars. The study is motivated to address one of the most relevant queries that whether the dominant dynamical processes leading to the observed γ\gamma-ray variability are of deterministic or stochastic nature. For the purpose, we perform Recurrence Quantification Analysis of the blazars and directly measure the quantities which suggest that the dynamical processes in blazar could be a combination of deterministic and stochastic processes, while some of the source light curves revealed significant deterministic content. The result with possible implication of strong disk-jet connection in blazars could prove to be significantly useful in constructing models that can explain the rich and complex multi-wavelength observational features in active galactic nuclei. In addition, we estimate the dynamical timescales, so called "trapping timescales", in the order of a few weeks.
We aim to understand what drives the IRX-\beta dust attenuation relation at intermediate redshift (0.5 < z < 0.8) in star-forming galaxies. We investigate the role of various galaxy properties in shaping this observed relation. We use robust [O ii] {\lambda}3727, [O iii] {\lambda}{\lambda}4959, 5007, and H\beta line detections of our statistical sample of 1049 galaxies to estimate the gas-phase metallicities. We derive key physical properties that are necessary to study galaxy evolution, such as the stellar masses and the star formation rates, using the spectral energy distribution fitting tool CIGALE. Equivalently, we study the effect of galaxy morphology (mainly the Sérsic index n and galaxy inclination) on the observed IRX-\beta scatter. We also investigate the role of the environment in shaping dust attenuation in our sample. We find a strong correlation of the IRX-\beta relation on gas-phase metallicity in our sample, and also strong correlation with galaxy compactness characterized by the Sérsic indexes. Correlations are also seen with stellar masses, specific star formation rates and the stellar ages of our sources. Metallicity strongly correlates with the IRX-\beta scatter, this also results from the older stars and higher masses at higher beta values. Galaxies with higher metallicities show higher IRX and higher beta values. The correlation with specific dust mass strongly shifts the galaxies away from the IRX-\beta relation towards lower \b{eta} values. We find that more compact galaxies witness a larger amount of attenuation than less compact galaxies. There is a subtle variation in the dust attenuation scatter between edge-on and face-on galaxies, but the difference is not statistically significant. Galaxy environments do not significantly affect dust attenuation in our sample of star-forming galaxies at intermediate redshift.
Context. Ongoing and upcoming large spectroscopic surveys are drastically increasing the number of observed quasar spectra, requiring the development of fast and accurate automated methods to estimate spectral continua. Aims. This study evaluates the performance of three neural networks (NN) - an autoencoder, a convolutional NN (CNN), and a U-Net - in predicting quasar continua within the rest-frame wavelength range of 1020 A˚1020~\text{\AA} to 2000 A˚2000~\text{\AA}. The ability to generalize and predict galaxy continua within the range of 3500 A˚3500~\text{\AA} to 5500 A˚5500~\text{\AA} is also tested. Methods. The performance of these architectures is evaluated using the absolute fractional flux error (AFFE) on a library of mock quasar spectra for the WEAVE survey, and on real data from the Early Data Release observations of the Dark Energy Spectroscopic Instrument (DESI) and the VIMOS Public Extragalactic Redshift Survey (VIPERS). Results. The autoencoder outperforms the U-Net, achieving a median AFFE of 0.009 for quasars. The best model also effectively recovers the Lyα\alpha optical depth evolution in DESI quasar spectra. With minimal optimization, the same architectures can be generalized to the galaxy case, with the autoencoder reaching a median AFFE of 0.014 and reproducing the D4000n break in DESI and VIPERS galaxies.
Magnetic fields, together with cosmic rays (CRs), play an important role in the dynamics and evolution of galaxies, but are difficult to estimate. Energy equipartition between magnetic fields and CRs provides a convenient way to approximate magnetic field strength from radio observations. We present a new approach for calculating the equipartition magnetic field strength based on Bayesian methods. In this approach, the magnetic field is a random variable that is distributed according to a posterior distribution conditional on synchrotron emission and the size of the emitting region. It allows the direct application of the general formulas for total and polarized synchrotron radiation without the need to invert these formulas, which has limited the equipartition method to highly simplified cases. We have derived the equipartition condition for the case of different low-energy breaks, slopes, and high-energy cutoffs of power law spectra of the CR proton and electron distributions. The derived formalism was applied in the general case of a magnetic field consisting of both uniform and randomly oriented field components. The applied Bayesian approach naturally provides the uncertainties in the estimated magnetic field strengths resulting from the uncertainties in the observables and the assumed values of the unknown physical parameters. In the examples presented, we used two different Markov Chain Monte Carlo methods to generate the posterior distribution of the magnetic field. We have also developed a web application called BMAG that implements the described approach for different models and observational parameters of real sources.
Physical properties of galaxies are correlated with their local environment. Quantifying these environmental correlations is crucial for a better understanding of galaxy formation and evolution. In this work, we investigate how galaxy properties are correlated with the environment through spatial clustering measurements of galaxies. Using two-point correlation functions and marked correlation functions, we measure and compare the environmental dependence of colour, stellar mass, luminosities in the uu, gg, rr, JJ, and KK bands, star formation rate, and specific star formation rate. We use galaxy samples from the southern (G02 and G23) regions of the Galaxy and Mass Assembly (GAMA) survey. Furthermore, we explore how redshift completeness affects clustering measurements by comparing different subsets of the G02 region with varying redshift completeness. We show that the uru-r and grg-r colours correlate the most with the local environment, with stellar mass being the next most reliable indicator of the environment. We also demonstrate that redshift completeness has a significant effect on clustering measurements.
Compact Symmetric Objects (CSOs) are thought to represent the first step in the evolutionary path of radio galaxies. In this work, we investigate the X-ray emission of two CSOs confirmed to emit at GeV energies: PKS 1718-649 and TXS 1146+596. Unveiling the origin of their observed high-energy emission is crucial to establishing the physical parameters of the radio source and understanding how CSOs interact with the surrounding medium. We combined archival and new NuSTAR observations of PKS 1718-649 and TXS 1146+596 to have a broadband X-ray coverage. For both sources, we model the broadband spectral energy distribution, from radio band up to γ\gamma-rays, to derive their physical parameters. We also discuss the role of the ambient medium in confining the source expansion, which we investigate using X-ray obscuration. For the first time, we report on X-ray detections of PKS 1718-649 and 1146+596 with NuSTAR at energies higher than 10 keV. Combining Chandra and NuSTAR observations of TXS 1146+596, we reveal the presence of a multi-temperature thermal component dominating the soft X-ray spectrum, and we interpret this finding as indicative of an AGN feedback process in action in this source. In addition, we show that two emitting electrons populations are necessary to reproduce the observed broadband spectral energy distribution of TXS 1146+596: in our models, the X-ray emission could be produced either by synchrotron radiation or by a weak X-ray corona or an ADAF-type emission. Interestingly, an additional X-ray component, i.e. a weak corona, is also required for PKS 1718-649. Moreover, we argue that heavily obscured, and possibly frustrated, sources tend to show different radio sizes with respect to unobscured, free to expand, ones.
Long Gamma Ray Bursts (GRBs) originate from the collapse of massive, rotating stars. We aim to model the process of stellar collapse in the scenario of a self-gravitating collapsing star. We account for the changes in Kerr metric induced by the growth of the black hole, accretion of angular momentum, as well as the self-gravity effect due to a large mass of the collapsing stellar core falling onto black hole in a very short time. We also investigate the existence of accretion shocks in the collapsar, and role of magnetic field in their propagation. We compute the time-dependent axially-symmetric General Relativistic magnetohydrodynamic model of a collapsing stellar core in the dynamical Kerr metric. We explore the influence of self-gravity in such star, where the newly formed black hole is increasing the mass, and changing its spin. The Kerr metric evolves according to the mass and angular momentum changes during the collapse. We parameterize the rotation inside the star, and account for the presence of large-scale poloidal magnetic field. For the set of the global parameters, such as the initial black hole spin, and initial content of specific angular momentum in the stellar envelope, we determine the evolution of black hole parameters (mass and spin) and we quantify the strength of the gravitational instability, variability timescales and amplitudes. We find that the role of the gravitational instability measured by the value of the Toomre parameter is relatively important in the innermost regions of the collapsing star. The character of accretion rate variability strongly depends on the assumption of self-gravity in the model, and is also affected by the magnetic field. Additional factors are initial spin and rotation of the stellar core.
Monash University logoMonash UniversityChinese Academy of Sciences logoChinese Academy of SciencesUniversity of Notre Dame logoUniversity of Notre DameUC Berkeley logoUC BerkeleyUniversity College London logoUniversity College LondonNikhefNanjing University logoNanjing UniversityUniversity of Copenhagen logoUniversity of CopenhagenYonsei UniversityRadboud UniversityUniversity of Maryland logoUniversity of MarylandHuazhong University of Science and Technology logoHuazhong University of Science and TechnologyUniversité Paris-Saclay logoUniversité Paris-SaclayStockholm University logoStockholm UniversityLawrence Berkeley National Laboratory logoLawrence Berkeley National LaboratoryUniversité de GenèveSorbonne Université logoSorbonne UniversitéUniversity of HertfordshireUniversity of LeicesterIlia State UniversityKTH Royal Institute of Technology logoKTH Royal Institute of TechnologyUniversity College DublinClemson UniversityAix Marseille UniversityJagiellonian UniversityEuropean Southern Observatory logoEuropean Southern ObservatoryCNESPontificia Universidad Católica de ChileAstronomical Institute of the Czech Academy of SciencesUniversidad de ValparaísoBulgarian Academy of SciencesShanghai Astronomical ObservatoryXian Jiaotong UniversityUniversity of ValenciaNiels Bohr Institute, University of CopenhagenUniversity of SharjahUlugh Beg Astronomical InstituteINAF-Istituto di RadioastronomiaAstronomical Observatory of the Jagiellonian UniversityInstituto de Astrofísica de Andalucía, IAA-CSICINAF – Osservatorio Astronomico di RomaInstitut d'Astrophysique de ParisAstronomical Observatory of Taras Shevchenko National University of KyivNational Academy of Sciences of UkraineAbastumani Astrophysical ObservatoryHelwan UniversityUniversity of Belgrade - Faculty of MathematicsOskar Klein Centre, Department of Physics, Stockholm UniversityUniversité Paris Cité, CNRS, Astroparticule et CosmologieUniversité Côte d’Azur, Observatoire de la Côte d’AzurInstitut de Recherche sur les lois Fondamentales de l’Univers, CEA, Université Paris-SaclayUniversité de Paris, CNRS, Observatoire de ParisUniversity of Split, Faculty of scienceShamakhy Astrophysical ObservatoryOzGrav, School of Physics and Astronomy, Monash UniversityLESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, Université Paris CitéUniversité de Toulouse, CNRS, IRAPUniversitas PertaminaCRESST/NASA Goddard Space Flight Center* National and Kapodistrian University of AthensCosmic Dawn Center(DAWN)INAF Osservatorio Astronomico di CapodimonteINAF Osservatorio Astrofisico di ArcetriINAF Osservatorio di Astrofisica e Scienza dello Spazio di BolognaINAF Osservatorio Astronomico di Brera
GRB~230812B is a bright and relatively nearby (z=0.36z =0.36) long gamma-ray burst (GRB) that has generated significant interest in the community and has thus been observed over the entire electromagnetic spectrum. We report over 80 observations in X-ray, ultraviolet, optical, infrared, and sub-millimeter bands from the GRANDMA (Global Rapid Advanced Network for Multi-messenger Addicts) network of observatories and from observational partners. Adding complementary data from the literature, we then derive essential physical parameters associated with the ejecta and external properties (i.e. the geometry and environment) of the GRB and compare with other analyses of this event. We spectroscopically confirm the presence of an associated supernova, SN2023pel, and we derive a photospheric expansion velocity of v \sim 17×103\times10^3 km s1^{-1}. We analyze the photometric data first using empirical fits of the flux and then with full Bayesian Inference. We again strongly establish the presence of a supernova in the data, with a maximum (pseudo-)bolometric luminosity of 5.75×10425.75 \times 10^{42} erg/s, at 15.761.21+0.8115.76^{+0.81}_{-1.21} days (in the observer frame) after the trigger, with a half-max time width of 22.0 days. We compare these values with those of SN1998bw, SN2006aj, and SN2013dx. Our best-fit model favours a very low density environment ($\log_{10}({n_{\rm ISM}/{\rm cm}^{-3}}) = -2.38^{+1.45}_{-1.60}$) and small values for the jet's core angle θcore=1.540.81+1.02 deg\theta_{\rm core} = 1.54^{+1.02}_{-0.81} \ \rm{deg} and viewing angle θobs=0.760.76+1.29 deg\theta_{\rm obs} = 0.76^{+1.29}_{-0.76} \ \rm{deg}. GRB 230812B is thus one of the best observed afterglows with a distinctive supernova bump.
In every proposed unification scheme for Active Galactic Nuclei (AGN), an integral element is the presence of circumnuclear dust arranged in torus-like structures. A crucial model parameter in this context is the covering factor (CF), defined as the ratio between the infrared luminosity of the dusty torus LIRL_{\rm IR}, and the accretion disk bolometric luminosity LagnL_{\rm agn}. Our study aims to determine whether CF evolution is genuine or if selection effects significantly influence it. Based on cross-matched multiwavelength photometrical data from the five major surveys (SDSS, GALEX, UKIDSS, WISE, SPITZER), a sample of almost 2,000 quasars was derived. The main parameters of quasars, such as black hole masses and the Eddington ratios, were calculated based on the spectroscopic data. The data were divided into two redshift bins: Low-zz (redshift ~1) and High-zz (redshift ~2) quasars. We identified an issue with the accuracy of the WISE W4 filter. Whenever feasible, it is recommended to utilize SPITZER MIPS 24 μ\mum data. The calculated median CF values for the highest quality SPITZER data are comparable within errors log\log CFlowz=0.19±0.11_{\textrm{low}-z} = -0.19\pm 0.11 and log\log CFhighz=0.18±0.11_{\textrm{high}-z}= -0.18\pm 0.11. The Efron & Petrosian test confirmed the presence of luminosity evolution with redshift for both LIRL_{\rm IR} and LagnL_{\rm agn}. Both the Low-zz and High-zz samples exhibit a similar correlation between LagnL_{\rm agn} and LIRL_{\rm IR}. No discernible evolution of the CF was observed in the subsample of quasars with high SMBH mass bin or high luminosities. The relationship between LIRL_{\rm IR} and LagnL_{\rm agn} deviates slightly from the expected 1:1 scaling. However, no statistically significant dependence of CF on luminosities could be claimed across the entire dataset.
Large future sky surveys, such as the LSST, will provide optical photometry for billions of objects. This paper aims to construct a proxy for the far ultraviolet attenuation (AFUVp) from the optical data alone, enabling the rapid estimation of the star formation rate (SFR) for galaxies that lack UV or IR data. To mimic LSST observations, we use the deep panchromatic optical coverage of the SDSS Photometric Catalogue DR~12, complemented by the estimated physical properties for the SDSS galaxies from the GALEX-SDSS-WISE Legacy Catalog (GSWLC) and inclination information obtained from the SDSS DR7. We restricted our sample to the 0.025-0.1 z-spec range and investigated relations among surface brightness, colours, and dust attenuation in the far UV range for star-forming galaxies obtained from the spectral energy distribution (SED). {Dust attenuation is best correlated with (u-r) colour and the surface brightness in the u band (μu\rm \mu_{u}). We provide a dust attenuation proxy for galaxies on the star-forming main sequence, which can be used for the LSST or any other type of broadband optical survey. The mean ratio between the catalogue values of SFR and those estimated using optical-only SDSS data with the AFUVp prior calculated as Δ\DeltaSFR=log(SFR$_{\tiny{\mbox{this work}}}/SFR/SFR_{\tiny{}\texttt{GSWLC}}$) is found to be less than 0.1~dex, while runs without priors result in an SFR overestimation larger than 0.3~dex. The presence or absence of theAFUVp has a negligible influence on the stellar mass estimation (with Δ\DeltaMstar_{star} in the range from 0 to 0.15-0.15 dex). Forthcoming deep optical observations of the LSST Deep Drilling Fields, which also have multi-wavelength data, will enable one to calibrate the obtained relation for higher redshift galaxies and, possibly, extend the study towards other types of galaxies, such as early-type galaxies off the main sequence.
We present detailed spectral energy distribution (SED) modeling of 14 local ultraluminous infrared galaxies (ULIRGs) with outstanding photometric data from the literature covering the ultraviolet--infrared (FIR) and radio bands (\sim50 MHz to \sim30 GHz). We employ the CIGALE SED fitting code to model the ultraviolet--FIR--radio SED. For the radio-only SED modeling, we use the UltraNest package, leveraging its nested sampling algorithm. Combining the results from our previous study on 11 luminous infrared galaxies (LIRGs), we discuss the global astrophysical properties of a sample of 25 starburst galaxies (z &lt; 0.5). Their radio spectra are frequently characterized by bends and turnovers, with no indication of ULIRGs exhibiting more complicated SEDs than LIRGs despite showing more signs of interactions. Including radio measurements in the CIGALE modeling constrained the dust luminosity and star formation rate (SFR) estimates by more than 1 order of magnitude better than previously reported for starburst galaxies. We show that total and nonthermal radio luminosity at 1.4 and 4.8 GHz frequencies can be good estimators of recent SFRs for all LIRGs and those ULIRGS with an insignificant influence of active galactic nuclei. A weaker but still significant correlation is observed between radio SFRs at 1.4 GHz and old (averaged over 100 Myr) SFRs based on SED modeling, indicative of multiple episodes of starburst activity during their lifetime. The thermal radio luminosity at 4.8 GHz is a better tracer of recent star formation than the thermal luminosity at 1.4 GHz. Statistically, our modeled nonthermal radio spectral indices do not significantly correlate with redshift, stellar mass, SFR, specific SFR, and dust mass.
Galaxy mergers play a crucial role in galaxy evolution. However, the correlation between mergers and the local environment of galaxies is not fully understood. We aim to address the question of whether galaxy mergers prefer denser or less dense environments by quantifying the spatial clustering of mergers and non-mergers. We use two different indicators to classify mergers and non-mergers - classification based on a deep learning technique (ff) and non-parametric measures of galaxy morphology, Gini-M20M_{20} (gg). We used a set of galaxy samples in the redshift range 0.1 &lt; z &lt; 0.15 from the Galaxy and Mass Assembly (GAMA) survey with a stellar mass cut of \log (M_{\star}/M_{\odot} ) &gt; 9.5. We measured and compared the two-point correlation function (2pCF) of mergers and non-mergers classified using the two merger indicators ff and gg. We measured the marked correlation function (MCF), in which the galaxies are weighted by ff to probe the environmental dependence of galaxy mergers. We do not observe a statistically significant difference between the clustering strengths of mergers and non-mergers obtained using 2pCF. However, using the MCF measurements with ff as a mark, we observe an anti-correlation between the likelihood of a galaxy being a merger and its environment. Our results emphasise the advantage of MCF over 2pCF in probing the environmental correlations. Based on the MCF measurements, we conclude that the galaxy mergers prefer to occur in the under-dense environments on scales &gt; 50 \, h^{-1} \mathrm{kpc} of the large-scale structure (LSS). We attribute this observation to the high relative velocities of galaxies in the densest environments that prevent them from merging.
Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy density in the Universe. The simplest option for this "dark energy" corresponds to a cosmological constant, perhaps related to the quantum vacuum energy. Physically viable alternatives invoke either the presence of a scalar field with an evolving equation of state, or extensions of general relativity involving higher-order curvature terms or extra dimensions. Although they produce similar expansion rates, different models predict measurable differences in the growth rate of large-scale structure with cosmic time. A fingerprint of this growth is provided by coherent galaxy motions, which introduce a radial anisotropy in the clustering pattern reconstructed by galaxy redshift surveys. Here we report a measurement of this effect at a redshift of 0.8. Using a new survey of more than 10,000 faint galaxies, we measure the anisotropy parameter b = 0.70 +/- 0.26, which corresponds to a growth rate of structure at that time of f = 0.91 +/- 0.36. This is consistent with the standard cosmological-constant model with low matter density and flat geometry, although the error bars are still too large to distinguish among alternative origins for the accelerated expansion. This could be achieved with a further factor-of-ten increase in the sampled volume at similar redshift.
Conventional studies of galaxy clustering within the framework of halo models typically assume that the density profile of all dark matter haloes can be approximated by the Navarro-Frenk-White (NFW) spherically symmetric profile. However, both modern N-body simulations and observational data suggest that most haloes are either oblate or prolate, and almost never spherical. In this paper we present a modified model of the galaxy correlation function. In addition to the five "classical" HOD parameters proposed by Zheng et al. 2007, it includes an additional free parameter ϕ\phi in the modified NFW density profile describing the asymmetry of the host dark matter halo. Using a subhalo abundance matching model (SHAM), we populate galaxies within BolshoiP N-body simulations. We compute the projected two-point correlation function wp(rp)w_p(r_p) for six stellar mass volume limited galaxy samples. We fit our model to the results, and then compare the best-fit asymmetry parameter ϕ\phi (and other halo parameters) to the asymmetry of dark matter haloes measured directly from the simulations and find that they agree within 1σ\sigma. We then fit our model to the wp(rp)w_p(r_p) results from Zehavi et al. 2011 and compare halo parameters. We show that our model accurately retrieves the halo asymmetry and other halo parameters. Additionally, we find 26%2-6\% differences between the halo masses (logMmin\log M_{min} and logM1\log M_1) estimated by our model and "classical" HOD models. The model proposed in this paper can serve as an alternative to multiparameter HOD models, since it can be used for relatively small samples of galaxies.
Strong lensing systems, expected to be abundantly discovered by next-generation surveys, offer a powerful tool for studying cosmology and galaxy evolution. The connection between galaxy structure and cosmology through distance ratios highlights the need to examine the evolution of lensing galaxy mass density profiles. We propose a novel, dark energy-model-independent method to investigate the mass density slopes of lensing galaxies and their redshift evolution using an extended power-law (EPL) model. We employ a non-parametric approach based on Artificial Neural Networks (ANNs) trained on Type Ia Supernovae (SNIa) data to reconstruct distance ratios of strong lensing systems. These ratios are compared with theoretical predictions to estimate the evolution of EPL model parameters. Analyses conducted at three levels, including the combined sample, individual lenses, and binned groups, ensure robust and reliable estimates. A negative trend in the mass density slope with redshift is observed, quantified as γ/z=0.20±0.12\partial\gamma/\partial z = -0.20 \pm 0.12 under a triangular prior for anisotropy. This study demonstrates that the redshift evolution of density slopes in lensing galaxies can be determined independently of dark energy models. Simulations based on LSST Rubin Observatory forecasts, which anticipate 100,000 strong lenses, show that spectroscopic follow-up of just 10 percent of these systems can constrain the redshift evolution coefficient with uncertainty (Δγ/z\Delta\partial\gamma/\partial z) to 0.021. This precision distinguishes evolving and non-evolving density slopes, providing new insights into galaxy evolution and cosmology.
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