Search

Quasars are characterized by violent and large amplitude variability in all the observation wavelengths, and the analysis of optical variability is useful for developing theoretical models. Long-term optical variability data of quasar 3C 446 were collected from the University of Michigan Radio Astronomy Observatory database in the 4.8, 8.0, and 14.5 GHz radio bands from 1976 to 2012. Due to the complexity of the variability data, it's hard to study by the linear time series analysis methods. For learning more about non-linear characteristics of the temporal evolution of quasar variability, the Ensemble Empirical Mode Decomposition and nonlinear analysis are used to analyse chaotic dynamics, fractal properties, and periodicity. This paper focuses on whether there is a significant difference between the periodic and non-linear properties of the quasar variability before and after the removal of the periodic or chaotic components. It turns out that the variability of quasar 3C 446 in the radio bands consists of periodic, trend, and chaotic components, and the periodic and trend components are dominant. The periods of the variability after removing the chaotic and trend components are exactly the same as the periods of the original variability data, but the chaotic and fractal characteristics of the two are significantly different. The saturated correlation dimension indicates that the reconstruction of the dynamical system requires more independent parameters than the original optical variables after the removal of the periodic and trend components. The Kolmogorov entropy indicates that the loss of information is greater for the former than the latter, and the system is more chaotic and more complex. The Hurst value indicates that the self-similarity and long-range correlation are slightly stronger for the latter than the former. [ABSTRACT FROM AUTHOR]

We conducted a search for |$\textrm {H}\, \scriptstyle \mathrm{I}$| emission of the gas-rich galaxies in the Vela region (260° ≤ ℓ ≤ 290°, −2° ≤ b ≤ 1°) to explore the Vela Supercluster (VSCL) at V hel ∼ 18 000  |$\rm km\, s^{-1}$|⁠ , largely obscured by Galactic dust. Within the mostly Radio Frequency Interference-free band (250 < V hel < 25 000  |$\rm km\, s^{-1}$|⁠) of MeerKAT, the analysis focuses on 157 hexagonally distributed pointings extracted from the South African Radio Astronomy Observatory MeerKAT Galactic Plane Survey located in the Vela region (Vela−SMGPS). These were combined into 10 contiguous mosaics, covering an ∼90 square degrees area. Among the 843 |$\textrm {H}\, \scriptstyle \mathrm{I}$| detected sources, 39 were previously discovered in the H  i Parkes Zone of Avoidance survey (V hel < 12 000  |$\rm km\, s^{-1}$|⁠ ; rms ∼ 6  |$\rm mJy\, beam^{-1}$|⁠). With the improved rms level of the Vela−SMGPS, i.e. 0.29–0.56  |$\rm mJy\, beam^{-1}$|⁠ , our study unveils nearly 12 times more detections (471 candidates) in that same velocity range. We furthermore could identify 187 galaxy candidates with an |$\textrm {H}\, \scriptstyle \mathrm{I}$| mass limit reaching |$\log (M_{\rm HI}/\rm {\rm M}_{\odot }) = 9.44$| in the VSCL velocity range V hel ∼ 19 500 ± 3500  |$\rm km\, s^{-1}$|⁠. We find indications of two wall-like overdensities that confirm the original suspicion that these walls intersect at low latitudes around longitudes of ℓ ∼ 272°–278°. We also find a strong signature most likely associated with the Hydra/Antlia extension and evidence of a previously unknown narrow filament at V hel ∼ 12 000 |$\rm km\, s^{-1}$|⁠. This paper demonstrates the efficiency of systematic |$\textrm {H}\, \scriptstyle \mathrm{I}$| surveys with the Square Kilometre Array (SKA) precursor MeerKAT, even in the most obscured part of the Zone of Avoidance. [ABSTRACT FROM AUTHOR]

The morphology of galaxies is shaped by stellar activity, feedback, gas and dust properties, and interactions with surroundings, and can therefore provide insight into these processes. In this paper, we study the spatial offsets between stellar and interstellar medium emission in a sample of 54 main-sequence star-forming galaxies at z ∼ 4–6 observed with the Atacama Large Millimeter/submillimeter Array (ALMA), and drawn from the ALMA Large Program to INvestigate C+ at Early times (ALPINE). We find no significant spatial offset for the majority (∼70 per cent) of galaxies in the sample among any combination of [C  ii ], far-infrared continuum, optical, and ultraviolet emission. However, a fraction of the sample (∼30 per cent) shows offsets larger than the median by more than 3σ significance (compared to the uncertainty on the offsets), especially between [C  ii ] and ultraviolet emission. We find that these significant offsets are of the order of ∼0.5–0.7 arcsec, corresponding to ∼3.5–4.5 kiloparsecs. The offsets could be caused by a complex dust geometry, strong feedback from stars and active galactic nuclei, large-scale gas inflow and outflow, or a combination of these phenomena. However, our current analysis does not definitively constrain the origin. Future, higher resolution ALMA and JWST observations may help resolve the ambiguity. Regardless, since there exist at least some galaxies that display such large offsets, galaxy models and spectral energy distribution fitting codes cannot assume co-spatial emission in all main-sequence galaxies, and must take into account that the observed emission across wavelengths may be spatially segregated. [ABSTRACT FROM AUTHOR]

This article discusses the problems of origin and evolution and issues of numerical modeling of spherical systems, such as clusters of galaxies, globular clusters or E0 galaxies, characterized by massiveness and relatively old age, including up to 1000 bodies. First, observational data on galaxy clusters and their results are analyzed, including using a numerical method. Methods for numerical modeling of the evolution of spherical systems are studied. Two models are analyzed: the first is spherically homogeneous, with an isotropic distribution, and the second is with a particle distribution obeying the Plummer model. Changes in the position of bodies in the system and the distribution of velocities for different moments of time were obtained for each individual model. The calculation results are presented in the form of graphs. In the first model, at an early stage of evolution, the system collapses: a dense core is formed in the center, and a shell is formed around it. It is shown that over time the concentration of the nucleus decreases and it begins to stretch and the size of the system begins to increase. In this case, the distribution of bodies in the system obeys the Gaussian distribution and remains unchanged until the end of evolution. The second model also shows that at an early stage of evolution, the system collapses: then the system contracts and a compacted core forms in the center. The difference between the second model and the first is that a dense halo appears around the nucleus. It is found that sometimes in the early stages of evolution the system is slightly elongated and then tends to a spherical shape. It is also discovered that when solving the modeling of spherical systems, the choice of initial conditions plays an important role. [ABSTRACT FROM AUTHOR]

Recent work has pointed out the potential existence of a tight relation between the cosmological parameter Ωm, at fixed Ωb, and the properties of individual galaxies in state-of-the-art cosmological hydrodynamic simulations. In this paper, we investigate whether such a relation also holds for galaxies from simulations run with a different code that makes use of a distinct subgrid physics: Astrid. We also find that in this case, neural networks are able to infer the value of Ωm with a ∼10% precision from the properties of individual galaxies, while accounting for astrophysics uncertainties, as modeled in Cosmology and Astrophysics with MachinE Learning (CAMELS). This tight relationship is present at all considered redshifts, z ≤ 3, and the stellar mass, the stellar metallicity, and the maximum circular velocity are among the most important galaxy properties behind the relation. In order to use this method with real galaxies, one needs to quantify its robustness: the accuracy of the model when tested on galaxies generated by codes different from the one used for training. We quantify the robustness of the models by testing them on galaxies from four different codes: IllustrisTNG, SIMBA, Astrid, and Magneticum. We show that the models perform well on a large fraction of the galaxies, but fail dramatically on a small fraction of them. Removing these outliers significantly improves the accuracy of the models across simulation codes. [ABSTRACT FROM AUTHOR]

Galaxies' spectral energy distribution has been explored through the use of spectral synthesis codes, and these techniques have been essential in identifying many aspects of the current galaxy evolution model. Most of the spectral synthesis codes that have been developed so far are solely stellar and assume a negligible nebular contribution to the overall continuum. FADO (Fitting Analysis using Differential Evolution Optimisation) is the first spectral synthesis code to fit self-consistently stellar and nebular components. Diagnostic diagrams are powerful tools for classifying galaxies based on the emission line ratio of collisionally excited lines such as [OIII] λ 5007, [NII] λ 6584, [SII] λ 6716, 6731, [OI] λ 6300, and the Balmer recombination lines such as Hα, Hβ. This paper explores the impact of including nebular components on diagnostic diagrams. We investigated the results of the application of FADO to the Sloan Digital Sky Survey Data Release 8 using the data analysed by MPA-JHU, the Max Planck Institute for Astrophysics, and Johns Hopkins University. We found that in all diagnostic diagrams, the fluxes for FADO are higher than those for MPA-JHU; the difference is significant compared to the error in the flux measurement. FADO overestimates the flux ratio of all three diagnostic diagrams over MPA-JHU, but the overestimation is comparable with the line flux ratio errors. The results indicate that the inclusion of a nebular continuum is very important when fitting the spectral energy distribution as it increases the fluxes of all galaxies. However, there is a mild impact from the inclusion of nebular component analysis in the diagnostic diagrams used to classify the ionisation state of galaxies' interstellar medium. [ABSTRACT FROM AUTHOR]

In this series of papers, we present a simulation-based model for the non-linear clustering of galaxies based on separate modelling of clustering in real space and velocity statistics. In the first paper, we present an emulator for the real-space correlation function of galaxies, whereas the emulator of the real-to-redshift space mapping based on velocity statistics is presented in the second paper. Here, we show that a neural network emulator for real-space galaxy clustering trained on data extracted from the dark quest suite of N-body simulations achieves sub-per cent accuracies on scales 1 < r < 30 |$h^{-1} \, \mathrm{Mpc}$|⁠ , and better than 3 per cent on scales r < 1 |$h^{-1}\, \mathrm{Mpc}$| in predicting the clustering of dark-matter haloes with number density 10−3.5 |$(h^{-1}\, \mathrm{Mpc})^{-3}$|⁠ , close to that of SDSS LOWZ-like galaxies. The halo emulator can be combined with a galaxy–halo connection model to predict the galaxy correlation function through the halo model. We demonstrate that we accurately recover the cosmological and galaxy–halo connection parameters when galaxy clustering depends only on the mass of the galaxies' host halos. Furthermore, the constraining power in σ8 increases by about a factor of 2 when including scales smaller than 5 |$h^{-1} \, \mathrm{Mpc}$|⁠. However, when mass is not the only property responsible for galaxy clustering, as observed in hydrodynamical or semi-analytic models of galaxy formation, our emulator gives biased constraints on σ8. This bias disappears when small scales (r < 10 |$h^{-1}\, \mathrm{Mpc}$|⁠) are excluded from the analysis. This shows that a vanilla halo model could introduce biases into the analysis of future data sets. [ABSTRACT FROM AUTHOR]

We report a new test of modified gravity theories using the large-scale structure of the Universe. This paper is the first attempt to (1) apply a joint analysis of the anisotropic components of galaxy two- and three-point correlation functions (2 and 3PCFs) to actual galaxy data and (2) constrain the non-linear effects of degenerate higher-order scalar-tensor (DHOST) theories on cosmological scales. Applying this analysis to the Baryon Oscillation Spectroscopic Survey (BOSS) data release 12, we obtain the lower bounds of −1.655 < ξt and −0.504 < ξs at the |$95{{\ \rm per\ cent}}$| confidence level on the parameters characterizing the time evolution of the tidal and shift terms of the second-order velocity field. These constraints are consistent with GR predictions of ξt = 15/1144 and ξs = 0. Moreover, they represent a 35-fold and 20-fold improvement, respectively, over the joint analysis with only the isotropic 3PCF. We ensure the validity of our results by investigating various quantities, including theoretical models of the 3PCF, window function corrections, cumulative S/N, Fisher matrices, and statistical scattering effects of mock simulation data. We also find statistically significant discrepancies between the BOSS data and the Patchy mocks for the 3PCF measurement. Finally, we package all of our 3PCF analysis codes under the name hitomi and make them publicly available so that readers can reproduce all the results of this paper and easily apply them to ongoing future galaxy surveys. [ABSTRACT FROM AUTHOR]

Rejuvenating galaxies are unusual galaxies that fully quench and then subsequently experience a "rejuvenation" event to become star-forming once more. Rejuvenation rates vary substantially in models of galaxy formation: 10%–70% of massive galaxies are expected to experience rejuvenation by z = 0. Measuring the rate of rejuvenation is therefore important for calibrating the strength of star-formation feedback mechanisms. However, these observations are challenging because rejuvenating systems blend in with normal star-forming galaxies in broadband photometry. In this paper, we use the galaxy spectral energy distribution-fitting code Prospector to search for observational markers that distinguish normal star-forming galaxies from rejuvenating galaxies. We find that rejuvenating galaxies have smaller Balmer absorption line equivalent widths (EWs) than normal star-forming galaxies. This is analogous to the well-known "K+A" or post-starburst galaxies, which have strong Balmer absorption due to A-stars dominating the light: in this case, rejuvenating systems have a lack of A-stars, instead resembling "O—A" systems. We find star-forming galaxies that have H β, H γ, and/or H δ absorption EWs ≲3 Å corresponds to a highly pure selection of rejuvenating systems. Interestingly, while this technique is highly effective at identifying mild rejuvenation, "strongly" rejuvenating systems remain nearly indistinguishable from star-forming galaxies due to the well-known stellar outshining effect. We conclude that measuring Balmer absorption line EWs in star-forming galaxy populations is an efficient method to identify rejuvenating populations, and discuss several techniques to either remove or resolve the nebular emission which typically lies on top of these absorption lines. [ABSTRACT FROM AUTHOR]

Strengthening the synergy between simulations and observations is essential to test galaxy formation and evolution theories. To achieve this goal, in the first paper of this series, we presented a method to generate mock SDSS-IV/Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) integral-field spectroscopic galaxy observations from cosmological simulations. In this second paper, we build the iMaNGA catalogue consisting of ∼1000 unique galaxies from the TNG50 cosmological simulations, selected to mimic the SDSS-IV/MaNGA-Primary sample selection. Here, we present and discuss the iMaNGA sample and its comparison to the MaNGA Primary catalogue. The iMaNGA sample well recovers the MaNGA-Primary sample in terms of stellar mass versus angular size relation and spatial resolution. The Sérsic index versus angular size relation, instead, is not reproduced well by the simulations, mostly because of a paucity of high-mass elliptical galaxies in TNG50. We also investigate our ability to recover the galaxy kinematics and stellar population properties with full-spectral fitting. We demonstrate that 'intrinsic' and 'recovered' stellar kinematics, stellar ages, and metallicities are consistent, with residuals compatible with zero within 1σ. Also 'intrinsic' and 'recovered' star formation histories display a great resemblance. We conclude that our mock generation and spectral fitting processes do not distort the 'intrinsic' galaxy properties. Therefore, in the third paper of this series, we can meaningfully test the cosmological simulations, comparing the stellar population properties and kinematics of the iMaNGA mock galaxies and the MaNGA observational results. [ABSTRACT FROM AUTHOR]

We present kinematics of six local extremely metal-poor galaxies (EMPGs) with low metallicities (0.016–0.098 Z ⊙) and low stellar masses (104.7–107.6 M ⊙). Taking deep medium/high-resolution (R ∼ 7500) integral-field spectra with 8.2 m Subaru, we resolve the small inner velocity gradients and dispersions of the EMPGs with H α emission. Carefully masking out substructures originating by inflow and/or outflow, we fit three-dimensional disk models to the observed H α flux, velocity, and velocity dispersion maps. All the EMPGs show rotational velocities (v rot) of 5–23 km s−1 smaller than the velocity dispersions (σ 0) of 17–31 km s−1, indicating dispersion-dominated (v rot/ σ 0 = 0.29–0.80 < 1) systems affected by inflow and/or outflow. Except for two EMPGs with large uncertainties, we find that the EMPGs have very large gas-mass fractions of f gas ≃ 0.9–1.0. Comparing our results with other H α kinematics studies, we find that v rot/ σ 0 decreases and f gas increases with decreasing metallicity, decreasing stellar mass, and increasing specific star formation rate. We also find that simulated high- z (z ∼ 7) forming galaxies have gas fractions and dynamics similar to the observed EMPGs. Our EMPG observations and the simulations suggest that primordial galaxies are gas-rich dispersion-dominated systems, which would be identified by the forthcoming James Webb Space Telescope observations at z ∼ 7. [ABSTRACT FROM AUTHOR]

Although I had not previously been aware of Jean Ginibre's work on random matrices, beginning in 1978 I became an admirer of his many papers on nonlinear waves in collaboration with Giorgio Velo. Their papers were amazingly profound and inspirational. I subsequently met Jean and Giorgio many times. I especially remember the pleasant time Jean and I spent together at a meeting in 2001 at Hokkaido University dedicated to the memory of the great Tosio Kato. The present announcement is a very brief summary of some of my recent mathematical work, joint with Yilun Wu, concerning a simple model of galaxies. [ABSTRACT FROM AUTHOR]

The Galaxy's stellar halo seems to be a tangle of disrupted systems that have been tidally stretched out into streams. Each stream approximately delineates an orbit in the Galactic force-field. In the first paper in this series, we showed that all six phase-space coordinates of each point on an orbit can be reconstructed from the orbit's path across the sky and measurements of the line-of-sight velocity along the orbit. In this paper, we complement this finding by showing that the orbit can also be reconstructed if we know proper motions along the orbit rather than the radial velocities. We also show that accurate proper motions of stream stars would enable distances to be determined to points on the stream that are independent of any assumption about the Galaxy's gravitational potential. Such ‘Galactic parallaxes’ would be as fundamental as conventional trigonometric parallaxes, but measurable to distances ∼70 times further. [ABSTRACT FROM AUTHOR]

We present Keck/LRIS follow-up spectroscopy for 13 photometric candidates of extremely metal-poor galaxies (EMPGs) selected by a machine-learning technique applied to the deep (∼26 AB mag) optical and wide-area (∼500 deg2) Subaru imaging data in the EMPRESS survey. Nine out of the 13 candidates are EMPGs with an oxygen abundance (O/H) less than ∼10% solar value (O/H)⊙, and four sources are contaminants of moderately metal-rich galaxies or no emission-line objects. Notably, two out of the nine EMPGs have extremely low stellar masses and oxygen abundances of 5 Ă— 104â€"7 Ă— 105 M ⊙ and 2%â€"3% (O/H)⊙, respectively. With a sample of five EMPGs with (Fe/O) measurements, two (three) of which are taken from this study (the literature), we confirm that two EMPGs with the lowest (O/H) ratios of ∼2% (O/H)⊙ show high (Fe/O) ratios of ∼0.1, close to the solar abundance ratio. Comparing galaxy chemical enrichment models, we find that the two EMPGs cannot be explained by a scenario of metal-poor gas accretion/episodic star formation history due to their low (N/O) ratios. We conclude that the two EMPGs can be reproduced by the inclusion of bright hypernovae and/or hypothetical pair-instability supernovae (SNe) preferentially produced in a metal-poor environment. This conclusion implies that primordial galaxies at z ∼ 10 could have a high abundance of Fe that did not originate from Type Ia SNe with delays and that Fe may not serve as a cosmic clock for primordial galaxies. [ABSTRACT FROM AUTHOR]

Observations indicate that the star formation rate (SFR) of nuclear rings varies considerably with time and is sometimes asymmetric rather than being uniform across a ring. To understand what controls temporal and spatial distributions of ring star formation, we run semiglobal, hydrodynamic simulations of nuclear rings subject to time-varying and/or asymmetric mass inflow rates. These controlled variations in the inflow lead to variations in the star formation, while the ring orbital period (18 Myr) and radius (600 pc) remain approximately constant. We find that both the mass inflow rate and supernova feedback affect the ring SFR. An oscillating inflow rate with period Î" Ď„ in and amplitude 20 causes large-amplitude (a factor of ≳5), quasi-periodic variations of the SFR when Î" Ď„ in ≳ 50 Myr. We find that the time-varying interstellar medium (ISM) weight and midplane pressure track each other closely, establishing an instantaneous vertical equilibrium. The measured time-varying depletion time is consistent with the prediction from self-regulation theory provided the time delay between star formation and supernova feedback is taken into account. The supernova feedback is responsible only for small-amplitude (a factor of ∼2) fluctuations of the SFR with a timescale ≲40 Myr. Asymmetry in the inflow rate does not necessarily lead to asymmetric star formation in nuclear rings. Only when the inflow rate from one dust lane is suddenly increased by a large factor do the rings undergo a transient period of lopsided star formation. [ABSTRACT FROM AUTHOR]

Compact star-forming clumps observed in distant galaxies are often suggested to play a crucial role in galaxy assembly. In this paper, we use a novel approach of applying finite-resolution deconvolution on ground-based images of the COSMOS field to resolve 20,185 star-forming galaxies (SFGs) at 0.5 < z < 2 to an angular resolution of 0.″3 and study their clump fractions. A comparison between the deconvolved images and HST images across four different filters shows good agreement and validates image deconvolution. We model spectral energy distributions using the deconvolved 14-band images to provide resolved surface brightness and stellar-mass density maps for these galaxies. We find that the fraction of clumpy galaxies decreases with increasing stellar masses and with increasing redshift: from ∼30% at z ∼ 0.7 to ∼50% at z ∼ 1.7. Using abundance matching, we also trace the progenitors for galaxies at z ∼ 0.7 and measure the fractional mass contribution of clumps toward their total mass budget. Clumps are observed to have a higher fractional mass contribution toward galaxies at higher redshift: increasing from ∼1% at z ∼ 0.7 to ∼5% at z ∼ 1.7. Finally, the majority of clumpy SFGs have higher specific star formation rates (sSFR) compared to the average SFGs at fixed stellar mass. We discuss the implication of this result for in situ clump formation due to disk instability. [ABSTRACT FROM AUTHOR]

Context. Time-delay lensing is a powerful tool for measuring the Hubble constant H0. However, in order to obtain an accurate estimate of H0 from a sample of time-delay lenses, very good knowledge of the mass structure of the lens galaxies is needed. Strong lensing data on their own are not sufficient to break the degeneracy between H0 and the lens model parameters on a single object basis. Aims. The goal of this study is to determine whether it is possible to break the H0-lens structure degeneracy with the statistical combination of a large sample of time-delay lenses, relying purely on strong lensing data with no stellar kinematics information. Methods. I simulated a set of 100 lenses with doubly imaged quasars and related time-delay measurements. I fitted these data with a Bayesian hierarchical method and a flexible model for the lens population, emulating the lens modelling step. Results. The sample of 100 lenses on its own provides a measurement of H0 with 3% precision, but with a −4% bias. However, the addition of prior information on the lens structural parameters from a large sample of lenses with no time delays, such as that considered in Paper I, allows for a 1% level inference. Moreover, the 100 lenses allow for a 0.03 dex calibration of galaxy stellar masses, regardless of the level of prior knowledge of the Hubble constant. Conclusions. Breaking the H0-lens model degeneracy with lensing data alone is possible, but 1% measurements of H0 require either many more than 100 time-delay lenses or knowledge of the structural parameter distribution of the lens population from a separate sample of lenses. [ABSTRACT FROM AUTHOR]

We present the photometric decomposition of spiral galaxies seen at a very large, almost edge-on, angle to the observer. Our sample contains about 150 galaxies of the Sc–Sd morphological types with apparent axis ratios in the B-band. This type of galaxies is of special interest, because their phenomenon is difficult to explain within the modern hierarchical model of galaxy formation. In addition, the galaxies seen at an angle to the observer i ~ 90° allow to study the vertical matter distribution. We used the Pan-STARRS sky survey data in the g-, r-, i-, z-, and y-bands. Our two-component decomposition model included a bulge and a disk. The paper presents the study of this sample including the search for correlations between the parameters obtained during the decomposition, as well as the results of comparing the parameters with the data from the EGIS catalog of visible edge-on galaxies for overlapping objects. [ABSTRACT FROM AUTHOR]

Due to observational constraints, our detailed knowledge of stellar populations, formation, and evolution of galaxies is limited to a few dozen galaxies located in the Local Group. The Local Group of galaxies offers a unique opportunity to construct the formation histories and probe the structure and dynamics of many dwarf galaxies surrounding the Milky Way and Andromeda and of isolated dwarf galaxies. In this regard, we monitored the majority of galaxies in the Local Group, including the M33 galaxy and satellites galaxies surrounding the Milky Way and Andromeda galaxy, as well as isolated dwarf galaxies. We identified stellar populations and based on light curve analysis, the cool evolved stars pulsating in the fundamental mode were identified. In this paper, first, we will present the results we obtained for SFH and dust production rate in individual galaxies separately to answer how different types of galaxies have been formed and evolved over cosmic time. Then, we will discuss whether the mass return from dusty evolved stars can provide enough gas reservoirs to sustain the star formation or even rejuvenate the dwarf galaxy, as some seem to harbor relatively young stars. [ABSTRACT FROM AUTHOR]

The hosts of OH megamaser (OHM) are luminous infrared galaxies (LIRGs), in fact 1/3 of them are ultra-luminous infrared galaxies (ULIRGs), which imply that OHM phenomena should be related to the infrared radiation field. In this paper, we investigate the far infrared (FIR) properties of OHM host galaxies, through detailed infrared data covering broad bands. All known OHM sources and one control sample of (U)LIRGs without maser detections (non-OHM sources) are cross-identified with AKARI and Herschel photometric catalogs. Comparative analysis on the spectral energy distribution (SED) with broad coverage from J to 350 μ m (taken from 2MASS, WISE, Spitzer, and AKARI and Herschel archive data) shows that the OHM sources tend to have higher FIR luminosities than those of the non-OHM sources, which are more pronounced in the SED range covered by the AKARI. These are consistent with our statistical results of the FIR luminosities distribution of both the samples, which show that the OHM sources tend to have higher FIR luminosities, especially, at short FIR wavelength (i.e., the 65 and 90 μ m). However, the non-OHM sources tend to have much stronger emission than those of OHM sources at both the near infrared (NIR) and middle infrared (MIR) bands. The statistic analysis of the color–color properties at MIR and FIR bands shows that the OHM sources have much cooler MIR and warmer FIR colors than non-OHM sources. These clues could help us to choose OHM candidates for future OHM surveys with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), where the OHM detection rate may exceed 40%. Further, one significant correlation of L OH ∝ L T FIR 1.18 ± 0.11 can be found between the maser luminosity and total FIR luminosity of OHM LIRGs. Combined with previous studies, we suggest that the OHM is dominantly pumped by the FIR, instead of NIR and MIR radiation fields. [ABSTRACT FROM AUTHOR]

The discovery of γ - ray emitting Seyfert galaxies has opened a new unified scheme of active galactic nuclei (AGN) in which jetted Seyfert galaxies are viewed as young counterparts of radio loud AGN. In this paper, we investigate the relationship between gamma-ray (γ - ray) properties of jetted Seyfert galaxies and those of traditionally radio galaxies, radio quasars and BL Lac objects. Results show that jetted Seyfert galaxies appear as low luminosity tail of the radio loud AGNs on the luminosity redshift (Lγ – z) plane, indicating an evolutionary link between them. Nevertheless, narrow-line Seyfert galaxies (NLS1s) do not share similar characteristics with Seyfert galaxies as they possess higher luminosities and redshift than Seyfert galaxies, suggestive that NLS1s are more evolved sources. Analyses of γ – ray and radio core-dominance show that for each subclass of jetted AGN, the beaming angle is wider for radio than for γ - ray emissions. While Seyferts and radio galaxies, on average, have similar low inclination to the line of sight, NLS1 objects have orientations similar to quasars and BL Lacs. There is a significant correlation (r ~ 0.7) between the γ - ray core dominance and γ - ray luminosity. The results are consistent with the revised unification scheme and suggests that NLS1s are highly beamed sources whose parent populations can be found among the regular Seyferts and/or radio galaxies [ABSTRACT FROM AUTHOR]

We studied the spectral signature of different components of the diffuse X-ray background (DXB), including Local Hot Bubble, solar wind charge exchange, galactic halo, and typically unresolved point sources (galaxies and active galactic nuclei), in the direction of the Chandra Deep Field South using the 4 Ms XMM-Newton survey and Chandra 4 Ms Source Catalog. In this paper, we present our results showing how the different components contribute to the DXB below 1 keV. In particular, we have found that ∼6% of the emission at 3 4 keV (all-sky average value ≈3 × 10−3 cm−6 pc), which is typically associated with galactic halo (GH) and circumgalactic medium (CGM), is, in fact, due to emission from typically unresolved galaxies. We will discuss the effect that this has on our understanding of GH and CGM and to our understanding of the missing CGM baryons. [ABSTRACT FROM AUTHOR]

We present a catalog of about 25,000 images of massive (M ⋆ ≥ 109 M ⊙) galaxies at redshifts 3 ≤ z ≤ 6 from the TNG50 cosmological simulation, tailored for observations at multiple wavelengths carried out with JWST. The synthetic images were created with the SKIRT radiative transfer code, including the effects of dust attenuation and scattering. The noiseless images were processed with the mirage simulator to mimic the Near Infrared Camera (NIRCam) observational strategy (e.g., noise, dithering pattern, etc.) of the Cosmic Evolution Early Release Science (CEERS) survey. In this paper, we analyse the predictions of the TNG50 simulation for the size evolution of galaxies at 3 ≤ z ≤ 6 and the expectations for CEERS to probe that evolution. In particular, we investigate how sizes depend on the wavelength, redshift, mass, and angular resolution of the images. We find that the effective radius accurately describes the three-dimensional half-mass–radius of the TNG50 galaxies. Sizes observed at 2 μ m are consistent with those measured at 3.56 μ m at all redshifts and masses. At all masses, the population of higher- z galaxies is more compact than their lower- z counterparts. However, the intrinsic sizes are smaller than the mock observed sizes for the most massive galaxies, especially at z ≲ 4. This discrepancy between the mass and light distributions may point to a transition in the galaxy morphology at z = 4–5, where massive compact systems start to develop more extended stellar structures. 2222 Data publicly released at https://www.tng-project.org/costantin22. [ABSTRACT FROM AUTHOR]

In this paper, we extend the Romanowsky and Fall (2012) results concerning the stellar angular momentum to the mass range 103 ≲ M*/M⊙ ≲ 1012, and using this result, we calculate the inner slope, α of haloes density profiles in terms of Vrot, by using a previous model of Del Popolo, taking into account the interactions between dark matter and baryons through dynamical friction. Using the McConnachie sample, and that of Romanowsky and Fall, based only on observations, we show that in the quoted sample the rotationally supported galaxies, and the pressure supported ones are divided by a break atM* ≃ 107.8M⊙. Then we show that the slope α flattens monotonically, from α ≃ − 1 to α ≃ 0. The flattening is due to the increase of specific angular momentum moving fromMilkyWay-type galaxies to disk dwarf galaxies. Since at M* < 107.8M⊙, non-rotational supported galaxies start to dominate, the inner slope steepens again. The paper also extends the main result of Del Popolo (2016) to morphologies different from spheroids, and disks, taking into account the different morphologies delimited by the quoted ones. We finally compared our results with Di Cintio SPH simulations. The two models differ mainly at stellar masses smaller than M* ≲ 107.8M⊙. In our model the inner slope is flatter than in simulations. This imply that even finding a cored, α ≃ 0.4, profile in dSphs with masses slightly smaller than ≃106M⊙ will not imply necessarily a problem for the ΛCDM mode, as predicted by some simulations. To check which one of the two model was better describing data in this region, we used the LITTLE THINGS data, and compared the two models through a χ2, finding that our model gives a better description of the data. [ABSTRACT FROM AUTHOR]

Context. Nucleation is a common phenomenon in all types of galaxies and at least 70% of them host nuclear star clusters (NSCs) in their centres. Many of the NSCs co-habit with supermassive black holes and follow similar scaling relations with host galaxy properties. Unlike black holes, NSCs, preserve the signature of their evolutionary path imprinted onto their kinematics and stellar populations. Thus their study provides us with important information about the formation of galactic nuclei. Aims. In this paper we explored the angular momentum of the nuclei of six intermediate mass (9.7 >  log(Mdyn/M⊙) > 10.6) early-type galaxies that host NSCs and are located in the Fornax cluster. Our goal was to derive a link between the nuclear angular momentum and the proposed formation scenarios of NSCs. Methods. We used adaptive optics assisted IFU observations with VLT/SINFONI to derive the spatially resolved stellar kinematics of the galaxy nuclei. We measured their specific stellar angular momenta λRe, and compared these with Milky Way globular clusters (GCs) and N-body simulations of NSC formation. Results. We found that all studied nuclei exhibit varied stellar kinematics. Their λRe and ellipticities are similar to Milky Way GCs. Five out of six galaxy nuclei are consistent with the λRe − ϵe of simulated NSCs embedded in a contaminating nuclear bulge that have formed via the in-spiralling and merging of GCs. Conclusion. It has previously been suggested that the NSCs in higher mass galaxies, such as those studied in this paper, form via dissipational sinking of gas onto the galactic nuclei with hints that some might also involve the merger of GCs. In this work we show that we cannot exclude the pure GC merging scenario as a viable path for the formation of NSCs. [ABSTRACT FROM AUTHOR]

It is crucial for a deeper understanding of the formation and evolution of galaxies in the Universe to study stellar mass (M *) and star formation rate (SFR). Traditionally, astronomers infer the properties of galaxies from spectra, which are highly informative, but expensive and hard to be obtained. Fortunately, modern sky surveys obtained a vast amount of high-spatial-resolution photometric images. The photometric images are obtained relatively economically than spectra, and it is very helpful for related studies if M * and SFR can be estimated from photometric images. Therefore, this paper conducted some preliminary researches and explorations on this regard. We constructed a deep learning model named Galaxy Efficient Network (GalEffNet) for estimating integrated M * and specific star formation rate (sSFR) from Dark Energy Spectroscopic Instrument galaxy images. The GalEffNet primarily consists of a general feature extraction module and a parameter feature extractor. The research results indicate that the proposed GalEffNet exhibits good performance in estimating M * and sSFR, with σ reaching 0.218 and 0.410 dex. To further assess the robustness of the network, prediction uncertainty was performed. The results show that our model maintains good consistency within a reasonable bias range. We also compared the performance of various network architectures and further tested the proposed scheme using image sets with various resolutions and wavelength bands. Furthermore, we conducted applicability analysis on galaxies of various sizes, redshifts, and morphological types. The results indicate that our model performs well across galaxies with various characteristics and indicate its potentials of broad applicability. [ABSTRACT FROM AUTHOR]

Variations in the dust emissivity index, |$\beta$|⁠ , within and between galaxies, are evidence that the chemistry and physics of dust must vary on large scales, although the nature of the physical and/or chemical variations is still unknown. In this paper, we estimate values of |$\beta$| and dust temperature for a sample of 109 dusty star-forming galaxies (DSFGs) over the range, |$2 \ \lt\ z \ \lt\ 6$|⁠. We compare the results obtained with both an optically thin model and a general opacity model, finding that our estimates of |$\beta$| are similar between the models but our estimates of dust temperature are not. We find no evidence of a change in |$\beta$| with redshift, with a median value of |$\beta = 1.96$| for the optically thin model with a confidence interval (16–84 per cent) of 1.67 to 2.35 for the population. Using simulations, we estimate the measurement errors from our procedure and show that the variation of |$\beta$| in the population results from intrinsic variations in the properties of the dust in DSFGs. At a fixed far-infrared luminosity, we find no evidence for a change in dust temperature, |$T_{\textrm {dust}}$|⁠ , with redshift. After allowing for the effects of correlated measurement errors, we find an inverse correlation between |$\beta$| and |$T_{\textrm {dust}}$| in DSFGs, for which there is also evidence in low-redshift galaxies. [ABSTRACT FROM AUTHOR]

The oldest stars in the Milky Way (born in the first few billion years) are expected to have a high density in the inner few kpc, spatially overlapping with the Galactic bulge. We use spectroscopic data from the Pristine Inner Galaxy Survey (PIGS) to study the dynamical properties of ancient, metal-poor inner Galaxy stars. We compute distances using starhorse , and orbital properties in a barred Galactic potential. With this paper, we release the spectroscopic AAT/PIGS catalogue (13 235 stars). We find that most PIGS stars have orbits typical for a pressure-supported population. The fraction of stars confined to the inner Galaxy decreases with decreasing metallicity, but many very metal-poor stars (VMP; [Fe/H] <−2.0) stay confined (⁠|$\sim 60~{{\ \rm per \, cent}}$| stay within 5 kpc). The azimuthal velocity vϕ also decreases between [Fe/H] = −1.0 and −2.0, but is constant for VMP stars (at ∼+40 km s−1). The carbon-enhanced metal-poor (CEMP) stars in PIGS appear to have similar orbital properties compared to normal VMP stars. Our results suggest a possible transition between two spheroidal components – a more metal-rich, more concentrated, faster rotating component, and a more metal-poor, more extended and slower/non-rotating component. We propose that the former may be connected to pre-disc in-situ stars (or those born in large building blocks), whereas the latter may be dominated by contributions from smaller galaxies. This is an exciting era where large metal-poor samples, such as in this work (as well as upcoming surveys, e.g. 4MOST), shed light on the earliest evolution of our Galaxy. [ABSTRACT FROM AUTHOR]

We present near-infrared JHK photometry for the resolved stellar populations in 13 nearby galaxies: NGC 6822, IC 1613, NGC 3109, Sextans B, Sextans A, NGC 300, NGC 55, NGC 7793, NGC 247, NGC 5253, Cen A, NGC 1313, and M83, acquired from the 6.5 m Baade–Magellan telescope. We measure distances to each galaxy using the J-region asymptotic giant branch (JAGB) method, a new standard candle that leverages the constant luminosities of color-selected, carbon-rich AGB stars. While only single-epoch, random-phase photometry is necessary to derive JAGB distances, our photometry is time-averaged over multiple epochs, thereby decreasing the contribution of the JAGB stars' intrinsic variability to the measured dispersions in their observed luminosity functions. To cross-validate these distances, we also measure near-infrared tip of the red giant branch (TRGB) distances to these galaxies. The residuals obtained from subtracting the distance moduli from the two methods yield an rms scatter of σ JAGB−TRGB = ±0.07 mag. Therefore, all systematics in the JAGB method and TRGB method (e.g., crowding, differential reddening, star formation histories) must be contained within these ±0.07 mag bounds for this sample of galaxies because the JAGB and TRGB distance indicators are drawn from entirely distinct stellar populations and are thus affected by these systematics independently. Finally, the composite JAGB star luminosity function formed from this diverse sample of galaxies is well described by a Gaussian function with a modal value of M J = –6.20 ± 0.003 mag (stat), indicating that the underlying JAGB star luminosity function of a well-sampled full star formation history is highly symmetric and Gaussian based on over 6700 JAGB stars in the composite sample. [ABSTRACT FROM AUTHOR]

In this paper, we discuss measurements of the stellar population and star-forming properties for 43 spectroscopically confirmed publicly available high-redshift z > 7 JWST galaxies in the JADES and CEERS observational programs. We carry out a thorough study investigating the relationship between spectroscopic features and photometrically derived ones, including from spectral energy distribution (SED) fitting of models, as well as morphological and structural properties. We find that the star formation rates (SFRs) measured from H β line emission are higher than those estimated from Bayesian SED fitting and ultraviolet (UV) luminosity, with ratios SFRH β/SFRUV ranging from ∼2 to 13. This is a sign that the star formation history is consistently rising given the time-scales of H β versus UV star formation probes. In addition, we investigate how well equivalent widths (EWs) of H β λ4861, [O  iii ] λ4959, and [O  iii ] λ5007 can be measured from photometry, finding that, on average, the EW derived from photometric excesses in filters is 30 per cent smaller than the direct spectroscopic measurement. We also discover that a stack of the line emitting galaxies shows a distinct morphology after subtracting imaging that contains only the continuum. This gives us a first view of the line or ionized gas emission from z > 7 galaxies, demonstrating that this material has a similar distribution, statistically, as the continuum. We also compare the derived SFRs and stellar masses for both parametric and non-parametric star formation histories, where we find that 35 per cent of our sample formed at least 30 per cent of their stellar mass in recent (<10 Myr) starburst events. [ABSTRACT FROM AUTHOR]

The environmental dependence of Type Ia supernova (SN Ia) luminosities is well established, and efforts are being made to find its origin. Previous studies typically use the currently observed status of the host galaxy. However, given the delay time between the birth of the progenitor star and the SN Ia explosion, the currently observed status may differ from the birth environment of the SN Ia progenitor star. In this paper, employing the chemical evolution and accurately determined stellar population properties of 44 early-type host galaxies, we, for the first time, estimate the SN Ia progenitor star birth environment, specifically [Fe/H]Birth and [α/Fe]Birth. We show that [α/Fe]Birth has a |$30.4^{\text{+10.6}}_{-10.1}{{\ \rm per\ cent}}$| wider range than the currently observed [α/Fe]Current, while the range of [Fe/H]Birth is not statistically different (⁠|$17.9^{\text{+26.0}}_{-27.1}{{\ \rm per\ cent}}$|⁠) to that of [Fe/H]Current. The birth and current environments of [Fe/H] and [α/Fe] are sampled from different populations (p -values of the Kolmogorov–Smirnov test <0.01). We find that light-curve fit parameters are insensitive to [Fe/H]Birth (<0.9σ for the non-zero slope), while a linear trend is observed with Hubble residuals (HRs) at the 2.4σ significance level. With [α/Fe]Birth, no linear trends (<1.1σ) are observed. Interestingly, we find that [α/Fe]Birth clearly splits the SN Ia sample into two groups: SN Ia exploded in [α/Fe]Birth-rich or [α/Fe]Birth-poor environments. SNe Ia exploded in different [α/Fe]Birth groups have different weighted-means of light-curve shape parameters: 0.81 ± 0.33 (2.5σ). They are thought to be drawn from different populations (p -value = 0.01). Regarding SN Ia colour and HRs, there is no difference (<1.0σ) in the weighted-means and distribution (p -value > 0.27) of each [α/Fe]Birth group. [ABSTRACT FROM AUTHOR]

Cosmological galaxy formation simulations are powerful tools to understand the complex processes that govern the formation and evolution of galaxies. However, evaluating the realism of these simulations remains a challenge. The two common approaches for evaluating galaxy simulations is either through scaling relations based on a few key physical galaxy properties, or through a set of pre-defined morphological parameters based on galaxy images. This paper proposes a novel image-based method for evaluating the quality of galaxy simulations using unsupervised deep learning anomaly detection techniques. By comparing full galaxy images, our approach can identify and quantify discrepancies between simulated and observed galaxies. As a demonstration, we apply this method to SDSS imaging and NIHAO simulations with different physics models, parameters, and resolution. We further compare the metric of our method to scaling relations as well as morphological parameters. We show that anomaly detection is able to capture similarities and differences between real and simulated objects that scaling relations and morphological parameters are unable to cover, thus indeed providing a new point of view to validate and calibrate cosmological simulations against observed data. [ABSTRACT FROM AUTHOR]

Current and future imaging surveys require photometric redshifts (photo-zs) to be estimated for millions of galaxies. Improving the photo-z quality is a major challenge but is needed to advance our understanding of cosmology. In this paper we explore how the synergies between narrow-band photometric data and large imaging surveys can be exploited to improve broadband photometric redshifts. We used a multi-task learning (MTL) network to improve broadband photo-z estimates by simultaneously predicting the broadband photo-z and the narrow-band photometry from the broadband photometry. The narrow-band photometry is only required in the training field, which also enables better photo-z predictions for the galaxies without narrow-band photometry in the wide field. This technique was tested with data from the Physics of the Accelerating Universe Survey (PAUS) in the COSMOS field. We find that the method predicts photo-zs that are 13% more precise down to magnitude iAB< 23; the outlier rate is also 40% lower when compared to the baseline network. Furthermore, MTL reduces the photo-z bias for high-redshift galaxies, improving the redshift distributions for tomographic bins with z > 1. Applying this technique to deeper samples is crucial for future surveys such as Euclid or LSST. For simulated data, training on a sample with iAB < 23, the method reduces the photo-z scatter by 16% for all galaxies with iAB < 25. We also studied the effects of extending the training sample with photometric galaxies using PAUS high-precision photo-zs, which reduces the photo-z scatter by 20% in the COSMOS field. [ABSTRACT FROM AUTHOR]

Context. The morphological classification of galaxies is considered a relevant issue and can be approached from different points of view. The increasing growth in the size and accuracy of astronomical data sets brings with it the need for the use of automatic methods to perform these classifications. Aims. The aim of this work is to propose and evaluate a method for the automatic unsupervised classification of kinematic morphologies of galaxies that yields a meaningful clustering and captures the variations of the fundamental properties of galaxies. Methods.We obtained kinematic maps for a sample of 2064 galaxies from the largest simulation of the EAGLE project that mimics integral field spectroscopy images. These maps are the input of a dimensionality reduction algorithm followed by a clustering algorithm. We analysed the variation of physical and observational parameters among the clusters obtained from the application of this procedure to different inputs. The inputs studied in this paper are (a) line-of-sight velocity maps for the whole sample of galaxies observed at fixed inclinations; (b) line-of-sight velocity, dispersion, and flux maps together for the whole sample of galaxies observed at fixed inclinations; (c) line-of-sight velocity, dispersion, and flux maps together for two separate subsamples of edge-on galaxies with similar amount of rotation; and (d) line-of-sight velocity, dispersion, and flux maps together for galaxies from different observation angles mixed. Results. The application of the method to solely line-of-sight velocity maps achieves a clear division between slow rotators (SRs) and fast rotators (FRs) and can differentiate rotation orientation. By adding the dispersion and flux information at the input, low-rotation edge-on galaxies are separated according to their shapes and, at lower inclinations, the clustering using the three types of maps maintains the overall information obtained using only the line-of-sight velocity maps. This method still produces meaningful groups when applied to SRs and FRs separately, but in the first case the division into clusters is less clear than when the input includes a variety of morphologies. When applying the method to a mixture of galaxies observed from different inclinations, we obtain results that are similar to those in our previous experiments with the advantage that in this case the input is more realistic. In addition, our method has proven to be robust: it consistently classifies the same galaxies viewed from different inclinations. [ABSTRACT FROM AUTHOR]

New measurements of 46 nearby galaxy centers in up to three transitions of HCN, HNC, and HCO+ combined with literature surveys establish a database of 130 galaxies measured in both HCN and HCO+, and 94 galaxies in HNC as well, allowing a systematic exploration of the relations between normalized luminosities and line ratios. The almost linear relations between luminosities are predominantly caused by distance effects and do not reflect galaxy physical properties. Individual galaxies show significant dispersion in both their luminosity and line ratio, which will be analyzed in more detail in a later paper. Very few line ratios correlate either with luminosities or with other line ratios. Only the normalized transition ladders of HCN and HCO+ and the J = 1 − 0 12CO/13CO isotopologue ratio are positively correlated with CO and far infrared (FIR) luminosity. On average, HCN and HCO+ have very similar intensities and trace the same gas. In galaxies dominated by an active nucleus, HCO+ intensities appear to be depressed relative to HCN intensities. Only a small fraction of CO emission is associated with gas emitting in HCN and HCO+, yet a significant fraction of even that gas appears to be translucent molecular gas. In the observed galaxy centers, the HCN/CO line intensity ratio is not a proxy for the dense gas fraction, and the FIR/HCN and FIR/CO ratios are not proxies for the star formation efficiency. A proper understandig of star formation requires a more appropriate determination of gas mass than provided by the intensities of individual HCN or CO transitions. The observed molecular line emission is fully consistent with UV-photon heating boosted by significant mechanical heating. The molecular gas sampled by HCN and HCO+ has low kinetic temperatures Tkin = 10 − 50 K, low densities nH = 104 − 105 cm−3, and low optical depths in the ground-state lines. Most of the gas sampled by CO has densities lower by one to two orders of magnitude. For a mechanical heating fraction of 0.5, a modest energy input of only G = 300 G0 is required. [ABSTRACT FROM AUTHOR]

In this paper, I review our understanding of how jet feedback works in star-forming galaxies. There are some interesting differences to radiative feedback from Active Galactic Nuclei (AGN). Jets act on galaxy haloes as well as on dense gas, for example in regularly rotating discs, where they can suppress star formation (particularly in the centre, negative feedback), but also enhance it (positive feedback). Jet feedback may produce turbulent, multi-phase gas structures where shocks contribute to the ionisation and is observed in connection with galactic outflows. The exact driving mechanism of these outflows is still unclear, but may be a combination of effects linked to star formation, jet-induced turbulence and radiative AGN feedback. Supermassive black holes in any galaxy can produce jets. Preferential radio detections in more massive galaxies can be explained with different conditions in the circumgalactic medium and, correspondingly, different jet–environment interactions. [ABSTRACT FROM AUTHOR]

Dirac, in 1937, proposed the potential variation of coupling constants derived from his large numbers hypothesis. Efforts have continued since then to constrain their variation by various methods, including astrophysical and cosmological observations. We briefly discuss several methods used for the purpose while focusing primarily on the use of supernovae type 1a, quasars, and gamma-ray bursts as cosmological probes for determining cosmological distances. Supernovae type Ia (SNeIa) are considered the best standard candles since their intrinsic luminosity can be determined precisely from their light curves. However, they have only been observed up to about redshift z = 2.3 , mostly at z ≤ 1.5 . Quasars are the brightest non-transient cosmic sources in the Universe. They have been observed up to z = 7.5 . Certain types of quasars can be calibrated well enough for their use as standard candles but with a higher degree of uncertainty in their intrinsic luminosity than SNeIa. Gamma-ray bursts (GRBs) are even brighter than quasars, and they have been observed up to z = 9.4 . They are sources of highly transient radiation lasting from tens of milliseconds to several minutes and, in rare cases, a few hours. However, they are even more challenging to calibrate as standard candles than quasars. Both quasars and GRBs use SNeIa for distance calibration. What if the standard candles' intrinsic luminosities are affected when the coupling constants become dynamic and depend on measured distances? Assuming it to be constant at all cosmic distances leads to the wrong constraint on the data-fitted model parameters. This paper uses our earlier finding that the speed of light c , the gravitational constant G , the Planck constant h , and the Boltzmann constant k vary in such a way that their variation is interrelated as G ~ c 3 ~ h 3 ~ k 3 / 2 with G ˙ / G = 3 c ˙ / c = 3 h ˙ / h = 1.5 k ˙ / k   = 3.90 ± 0.04 × 10 − 10   yr − 1 and corroborates it with SNeIa, quasars, and GRBs observational data. Additionally, we show that this covarying coupling constant model may be better than the standard Λ CDM model for using quasars and GRBs as standard candles and predict that the mass of the GRBs scales with z as 1 + z 1 / 3 − 1 . Noether's symmetry on the coupling constants is now transferred effectively to the constant in the function relating to their variation. [ABSTRACT FROM AUTHOR]

In this paper, we study the dynamical and statistical properties of the cosmic web and investigate their ability to infer the corresponding cosmological model. Our definition of the cosmic web is based on the local dimensionality of the gravitational collapse that classifies the cosmic web into four categories: voids, walls, filaments, and nodes. Our results show that each category has its specific non-Gaussian evolution over time and that these non-Gaussianities depend on the cosmological parameters. Nonetheless, the non-Gaussianities in each category exist even at early epochs when the matter field has a Gaussian distribution. Additionally, by using deep learning techniques, we show that leveraging the cosmic web information engenders an improved inference of cosmological parameters, when compared to merely using the matter field. [ABSTRACT FROM AUTHOR]

As galactic halos are not directly visible, there are many ambiguities regarding their composition and rotational velocity. Though most of the dark matter is non-baryonic, some fraction is, and it can be used to trace the halo rotation. Asymmetries in the CMB towards M31 had been seen in the Planck data and ascribed to the rotational Doppler shift of the M31 halo. Subsequently, the same methods were used in the direction of five other galaxies belonging to the Local Group, namely M33, M81, M82, NGC 5128, and NGC 4594. It had been proved that there could be stable clouds of gas and dust in thermal equilibrium with the CMB at 2.7 K, which had been called "virial clouds". In this paper, adopting this scenerio, an attempt is made to constrain the fraction of dust grains and gas molecules in the clouds. [ABSTRACT FROM AUTHOR]

We study the dependence of Lyα escape from galaxies on UV continuum size and luminosity using a sample of 40 Green Pea (GP) galaxies, which are the best local analogs of high-redshift Lyα emitters (LAEs). We use the Cosmic Origins Spectrograph near-ultraviolet images from the Hubble Space Telescope to measure the UV size and luminosity with 0.″047 spatial resolution. Like most galaxies the GPs show a log-normal size distribution. They also show a positive correlation between size and UV-continuum luminosity. The slope of the size-continuum luminosity relation for GPs is consistent with those of continuum-selected star-forming galaxies (SFGs) at low and high redshifts. A distinctive feature of GPs is a very compact typical radius of 0.33 kpc with a population spread (1σ) of 0.19 kpc. The peak of the size distribution and the intercept of the size–luminosity relation of GPs are noticeably smaller than those of continuum-selected SFGs at similar redshifts. There are statistically significant anticorrelations found between the circularized half-light radius (rcir,50), the Lyα equivalent width (EW(Lyα)), and the Lyα escape faction (), suggesting that small UV-continuum radii are crucial for Lyα emission. GPs and high-redshift LAEs have similar sizes, once spatial resolution effects are properly considered. Our results show that a compact small size is crucial for escape of Lyα photons, and that Lyα emitters show constant characteristic size independent of their redshift. [ABSTRACT FROM AUTHOR]

In this paper, we will study the large scale structure formation using the gravitational partition function. We will assertively argue that the system of gravitating galaxies can be analyzed using the Tsallis statistical mechanics. The divergences in the Tsallis gravitational partition function can be removed using the mathematical riches of the generalization of the dimensional regularization (GDR). The finite gravitational partition function thus obtained will be used to evaluate the thermodynamics of the system of galaxies and thus, to understand the clustering of galaxies in the universe. The correlation function which is beleived to contain the information of clustering of galaxies will also be discussed in this formalism. [ABSTRACT FROM AUTHOR]

Basing our analysis on ROGUE I, a catalog of over 32,000 radio sources associated with optical galaxies, we provide two diagnostics to select the galaxies where the radio emission is dominated by an active galactic nucleus (AGN), referred to in the paper as radio-AGNs. Each of these diagnostics can be applied independently. The first one, dubbed MIRAD, compares the flux FW3 in the W3 mid-infrared band of the Wide-field Infrared Survey Explorer telescope, with the radio flux at 1.4 GHz, F1.4. MIRAD requires no optical spectra. The second diagnostic, dubbed DLM, compares the 4000 Å break strength, Dn(4000), with the radio luminosity per unit stellar mass. The DLM diagram has already been used in the past, but not as stand-alone. For these two diagrams, we propose simple, empirical dividing lines that result in the same classification for the objects in common. These lines correctly classify as radio-AGN 99.5% of the extended radio sources in the ROGUE I catalog, and as star-forming galaxies 98%–99% of the galaxies identified as such by their emission-line ratios. Both diagrams clearly show that radio-AGNs are preferentially found among elliptical galaxies and among galaxies hosting the most massive black holes. Most of the radio sources classified as radio-AGNs in the MIRAD or DLM diagrams are either optically weak AGNs or retired galaxies. [ABSTRACT FROM AUTHOR]

Context. Anti-truncated lenticular galaxies (Type-III S0s) present tight scaling relations between their surface brightness photometric and structural parameters. Although several evolutionary models have been proposed for the formation of these structures, the observations of Type-III S0 galaxies are usually limited to the local Universe. Aims. We aim to compare the properties of Type-III discs in a sample of S0 galaxies at 0.2 < z < 0.6 with those of the local Universe. In this paper, we study the evolution of the photometric and structural scaling relations measured in the rest-frame R-band with z and the possible differences between the rest-frame (B − R) colours of the inner and outer disc profiles. Methods. We make use of a sample of 14 Type-III E/S0–S0 galaxies at 0.2 < z < 0.6 from the GOODS-N field identified and characterised in a previous paper. We study whether or not the correlations found in local Type-III S0 galaxies were present ~6 Gyr ago. We analyse the distribution of the surface brightness characteristic parameters (Rbreak, μbreak, hi, ho, μ0,i and μ0,o) as a function of the stellar mass and look to see if there is a significant change with z. We also derive their rest-frame (B − R) colour profiles. Finally, we compare these results with the predictions from a grid of SSP models. Results. We find that the inner and outer scale-lengths of Type-III S0 galaxies at 0.4 < z < 0.6 follow compatible trends and scaling relations with those observed in local S0 galaxies as a function of the break radius, Rbreak. We do not detect any significant differences between the location of Rbreak between z ~ 0.6 and z ~ 0 for a fixed stellar mass of the object, whereas the surface brightness at the break radius μbreak is ~1.5 mag arcsec-2 dimmer in the local Universe than at z ~ 0.6 for a fixed stellar mass. We find no significant differences in the (B − R) colour between the inner and outer profiles of the Type-III S0 galaxies at 0.2 < z < 0.6. Conclusions. In contrast to Type-II (down-bending) profiles, the anti-truncated surface brightness profiles of S0 galaxies present compatible Rbreak values and scaling relations during the last 6 Gyr. This result and the similarity of the colours of the inner and outer discs point to a highly scalable and stable formation process, probably more related to gravitational and dynamical processes than to the evolution of stellar populations. [ABSTRACT FROM AUTHOR]

Thanks to its high spectral resolution (~5 eV at 6 keV), the Soft X-ray Spectrometer (SXS) on board Hitomi enables us to measure the detailed structure of spatially resolved emission lines from highly ionized ions in galaxy clusters for the first time. In this series of papers, using the SXS we have measured the velocities of gas motions, metallicities and the multi-temperature structure of the gas in the core of the Perseus Cluster. Here, we show that when inferring physical properties from line emissivities in systems like Perseus, the resonant scattering effect should be taken into account. In the Hitomi waveband, resonant scattering mostly affects the Fe XXV Hea line (w)--the strongest line in the spectrum. The flux measured by Hitomi in this line is suppressed by a factor of ~1.3 in the inner ~30 kpc, compared to predictions for an optically thin plasma; the suppression decreases with the distance from the center. The w line also appears slightly broader than other lines from the same ion. The observed distortions of the w line flux, shape, and distance dependence are all consistent with the expected effect of the resonant scattering in the Perseus core. By measuring the ratio of fluxes in optically thick (w) and thin (Fe XXV forbidden, Heß, Lya) lines, and comparing these ratios with predictions from Monte Carlo radiative transfer simulations, the velocities of gas motions have been obtained. The results are consistent with the direct measurements of gas velocities from line broadening described elsewhere in this series, although the systematic and statistical uncertainties remain significant. Further improvements in the predictions of line emissivities in plasma models, and deeper observations with future X-ray missions offering similar or better capabilities to the Hitomi SXS, will enable resonant scattering measurements to provide powerful constraints on the amplitude and anisotropy of cluster gas motions. [ABSTRACT FROM AUTHOR]

We present spectroscopic identification of 32 new quasars and luminous galaxies discovered at 5.7 < z ≤ 6.8. This is the second in a series of papers presenting the results of the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which exploits the deep multi-band imaging data produced by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. The photometric candidates were selected by a Bayesian probabilistic algorithm, and then observed with spectrographs on the Gran Telescopio Canarias and the Subaru Telescope. Combined with the sample presented in the previous paper of this series, we have now identified 64 HSC sources over about 430 deg2, which include 33 high-z quasars, 14 high-z luminous galaxies, two [O III] emitters at z ∼ 0.8, and 15 Galactic brown dwarfs. The new quasars have considerably lower luminosity (M1450 ∼ −25 to −22 mag) than most of the previously known high-z quasars. Several of these quasars have luminous (>1043 erg s−1) and narrow (< 500 km s−1) Lyα lines, and also a possible mini broad-absorption-line system of N V λ1240 in the composite spectrum, which clearly separate them from typical quasars. On the other hand, the high-z galaxies have extremely high luminosities (M1450 ∼ −24 to −22 mag) compared to other galaxies found at similar redshifts. With the discovery of these new classes of objects, we are opening up new parameter spaces in the high-z Universe. Further survey observations and follow-up studies of the identified objects, including the construction of the quasar luminosity function at z ∼ 6, are ongoing. [ABSTRACT FROM AUTHOR]