We create mock X-ray observations of hot gas in galaxy clusters with a new extension of the L-Galaxies semianalytic model of galaxy formation,which includes the radial distribution of hot gas in each halo.Based on the...We create mock X-ray observations of hot gas in galaxy clusters with a new extension of the L-Galaxies semianalytic model of galaxy formation,which includes the radial distribution of hot gas in each halo.Based on the model outputs,we first build some mock light cones,then generate mock spectra with the SOXS package and derive the mock images in the light cones.Using the mock data,we simulate mock X-ray spectra for the ROSAT all-sky survey,and compare the mock spectra with the observational results.Then,we consider the design parameters of the HUBS mission and simulate the observation of the halo hot gas for HUBS as an important application of our mock work.We find:(1)our mock data match the observations by current X-ray telescopes.(2)The survey of hot baryons in resolved clusters by HUBS is effective below redshift 0.5,and the observations of the emission lines in point-like sources at z>0.5 by HUBS help us understand the hot baryons in the early universe.(3)By taking advantage of the large simulation box and flexibility in semi-analytic models,our mock X-ray observations provide the opportunity to select targets and observation strategies for forthcoming X-ray facilities.展开更多
The second moment of the stellar velocity within the effective radius,denoted by σ^(2)_(e),is a crucial quantity in galaxy studies,as it provides insight into galaxy properties and their mass distributions.However,la...The second moment of the stellar velocity within the effective radius,denoted by σ^(2)_(e),is a crucial quantity in galaxy studies,as it provides insight into galaxy properties and their mass distributions.However,large spectroscopic surveys typically do not measure σ_(e) directly,instead providing σ_(aper),the second moment of the stellar velocity within a fixed fiber aperture.In this paper,we derive an empirical aperture correction formula,given byσ_(aper)/σ_(e)=(R_(aper)/R_(e))^(α),using spatially resolved stellar kinematics extracted from approximately 10,000 Sloan Digital Sky Survey-Mapping Nearby Galaxies at Apache Point Observatory integral field unit observations.Our analysis reveals a strong dependence ofαon the r-band absolute magnitude M_(r),g-i color,and Sérsic index nSer,whereαvalues are lower for brighter,redder galaxies with higher Sérsic indices.Our results demonstrate that the aperture correction derived from previous literature on early-type galaxies cannot be applied to predict the aperture corrections for galaxies with intermediate Sérsic indices.We provide a lookup table ofαvalues for different galaxy types,with parameters in the ranges of-18>M_(r)>-24,0.4<g-i<1.6,and 0<n_(Ser)<8.A Python script is provided to obtain the correction factors from the lookup table.展开更多
We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9(z = 0.005)(hereafter J2306) and investigate whether it could be a Tidal Dwa...We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9(z = 0.005)(hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy(TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g-r color of 0.23 mag, irregular optical morphology and high-metallicity(12 +log(O/H) = 8.68 ± 0.14), making it an interesting galaxy to study in more detail. We find J2306 to be an H I rich galaxy with a large extended, unperturbed rotating H I disk. Using our H I data we estimated its dynamical mass and found the galaxy to be dark matter(DM) dominated within its H I radius. The quantity of DM, inferred from its dynamical mass, appears to rule out J2306 as an evolved TDG. A wide area environment search reveals J2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the H I morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity.Further detailed optical spectroscopic observations of J2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment.展开更多
The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark ...The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(La GRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known La GRLs,we confirm the correlation between radio power P_(1.4GHz)and stellar mass M_(*)of host galaxies.Most(25/35)La GRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P_(1.4GHz)-M_(*)relation,and the galaxy color,indicating that bluer galaxies at a fixed M_(*)tend to host more powerful radio lobes.Furthermore,the majority(31/36)of La GRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.展开更多
The structural parameters of a galaxy can be used to gain insight into its formation and evolution history.In this paper,we strive to compare the Milky Way’s structural parameters to other,primarily edge-on,spiral ga...The structural parameters of a galaxy can be used to gain insight into its formation and evolution history.In this paper,we strive to compare the Milky Way’s structural parameters to other,primarily edge-on,spiral galaxies in order to determine how our Galaxy measures up to the Local Universe.For our comparison,we use the galaxy structural parameters gathered from a variety of literature sources in the optical and near-infrared wave bands.We compare the scale length,scale height,and disk flatness for both the thin and thick disks,the thick-to-thin disk mass ratio,the bulge-to-total luminosity ratio,and the mean pitch angle of the Milky Way’s spiral arms to those in other galaxies.We conclude that many of the Milky Way’s structural parameters are largely ordinary and typical of spiral galaxies in the Local Universe,though the Galaxy’s thick disk appears to be appreciably thinner and less extended than expected from zoom-in cosmological simulations of Milky Way-mass galaxies with a significant contribution of galaxy mergers involving satellite galaxies.展开更多
This study introduces a novel convolutional neural network,the WISE Galaxy Classification Network(WGC),for classifying spiral and elliptical galaxies using Wide-field Infrared Survey Explorer(WISE)images.WGC attains a...This study introduces a novel convolutional neural network,the WISE Galaxy Classification Network(WGC),for classifying spiral and elliptical galaxies using Wide-field Infrared Survey Explorer(WISE)images.WGC attains an accuracy of 89.03%,surpassing the combined use of K-means or SVM with the Color-Color method in more accurately identifying galaxy morphologies.The enhanced variant,WGC_mag,integrates magnitude parameters with image features,further boosting the accuracy to 89.89%.The research also delves into the criteria for galaxy classification,discovering that WGC primarily categorizes dust-rich images as elliptical galaxies,corresponding to their lower star formation rates,and classifies less dusty images as spiral galaxies.The paper explores the consistency and complementarity of WISE infrared images with SDSS optical images in galaxy morphology classification.The SDSS Galaxy Classification Network(SGC),trained on SDSS images,achieved an accuracy of 94.64%.The accuracy reached 99.30% when predictions from SGC and WGC were consistent.Leveraging the complementarity of features in WISE and SDSS images,a novel variant of a classifier,namely the Multi-band Galaxy Morphology Integrated Classifier,has been developed.This classifier elevates the overall prediction accuracy to 95.39%.Lastly,the versatility of WGC was validated in other data sets.On the HyperLEDA data set,the distinction between elliptical galaxies and Sc,Scd and Sd spiral galaxies was most pronounced,achieving an accuracy of 90%,surpassing the classification results of the Galaxy Zoo 2 labeled WISE data set.This research not only demonstrates the effectiveness of WISE images in galaxy morphology classification but also represents an attempt to integrate multi-band astronomical data to enhance understanding of galaxy structures and evolution.展开更多
How galaxies assemble masses through their own star formation or interaction with the external environment is still an important topic in the field of galaxy formation and evolution.We use Value Added Catalogs with ga...How galaxies assemble masses through their own star formation or interaction with the external environment is still an important topic in the field of galaxy formation and evolution.We use Value Added Catalogs with galaxy features that are spatially and temporally resolved from Sloan Digital Sky Survey Data Release 17 to investigate the mass growth histories of early-type galaxies(ETGs)and late-type galaxies(LTGs).We find that the mass growth of ETGs is earlier than that of LTGs for massive galaxies(M_(*)>10^(10)M_⊙),while low-mass(M_(*)≤10^(10)M_⊙)ETGs have statistically similar mass assembly histories as low-mass LTGs.The stellar metallicity of all massive galaxies shows a negative gradient and basically does not change with time.However,in low-mass galaxies,the stellar metallicity gradient of elliptical galaxies is negative,and the stellar metallicity gradient of lenticular and spiral galaxies evolves from positive to negative.ETGs are not all in a high-density environment,but exhibit mass dependence.As the tidal strength increases,the star formation rate of low-mass ETGs rapidly decreases.These results support a picture where massive galaxies exhibit inside-out quenching mode,while low-mass galaxies show outside-in quenching mode.Environmental effects play an important role in regulating the mass assembly histories of low-mass ETGs.展开更多
We present a study of low surface brightness galaxies(LSBGs) selected by fitting the images for all the galaxies inα.40 SDSS DR7 sample with two kinds of single-component models and two kinds of two-component models(...We present a study of low surface brightness galaxies(LSBGs) selected by fitting the images for all the galaxies inα.40 SDSS DR7 sample with two kinds of single-component models and two kinds of two-component models(disk+bulge):single exponential,single sersic,exponential+deVaucular(exp+deV),and exponential+sérsic(exp+ser).Under the criteria of the B band disk central surface brightness μ_(0,disk)(B)≥22.5 mag arcsec^(-2) and the axis ratio b/a> 0.3,we selected four none-edge-on LSBG samples from each of the models which contain 1105,1038,207,and 75 galaxies,respectively.There are 756 galaxies in common between LSBGs selected by exponential and sersic models,corresponding to 68.42% of LSBGs selected by the exponential model and 72.83% of LSBGs selected by the sersic model,the rest of the discrepancy is due to the difference in obtaining μ_(0) between the exponential and sersic models.Based on the fitting,in the range of 0.5≤n≤1.5,the relation of μ_(0) from two models can be written as μ_(0,sérsic)-μ_(0,exp)=-1.34(n-1).The LSBGs selected by disk+bulge models(LSBG_(2)comps) are more massive than LSBGs selected by single-component models(LSBG_1comp),and also show a larger disk component.Though the bulges in the majority of our LSBG_(2)comps are not prominent,more than 60% of our LSBG_(2)comps will not be selected if we adopt a single-component model only.We also identified 31 giant low surface brightness galaxies(gLSBGs) from LSBG_(2)comps.They are located at the same region in the color-magnitude diagram as other gLSBGs.After we compared different criteria of gLSBGs selection,we find that for gas-rich LSBGs,M_(*)> 10^(10)M_⊙ is the best to distinguish between gLSBGs and normal LSBGs with bulge.展开更多
The star-forming clumps in star-bursting dwarf galaxies provide valuable insights into understanding the evolution of dwarf galaxies.In this paper,we focus on five star-bursting dwarf galaxies featuring off-centered c...The star-forming clumps in star-bursting dwarf galaxies provide valuable insights into understanding the evolution of dwarf galaxies.In this paper,we focus on five star-bursting dwarf galaxies featuring off-centered clumps in the Mapping Nearby Galaxies at Apache Point Observatory survey.Using the stellar population synthesis software Fitting Analysis using Differential evolution Optimization,we obtain the spatially resolved distribution of the star formation history,which allows us to construct the g-band images of the five galaxies at different ages.These images can help us to probe the evolution of the morphological structures of these galaxies.While images of a stellar population older than 1 Gyr are typically smooth,images of a stellar population younger than 1 Gyr reveal significant clumps,including multiple clumps which appear at different locations and even different ages.To study the evolutionary connections of these five galaxies to other dwarf galaxies before their star-forming clumps appear,we construct the images of the stellar populations older than three age nodes,and define them to be the images of the"host"galaxies.We find that the properties such as the central surface brightness and the effective radii of the hosts of the five galaxies are in between those of dwarf ellipticals(dEs)and dwarf irregulars(dIrrs),with two clearly more similar to dEs and one more similar to dIrrs.Among the five galaxies,8257-3704 is particularly interesting,as it shows a previous starburst event that is not quite visible from its gri image,but only visible from images of the stellar population at a few hundred million years.The star-forming clump associated with this event may have appeared at around 600 Myr ago and disappeared at around 40 Myr ago.展开更多
We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic index n<2) in a loca close major-merger galaxy pair sample (H-KPAIR).With data from new aperture photometries in the opt...We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic index n<2) in a loca close major-merger galaxy pair sample (H-KPAIR).With data from new aperture photometries in the optical and near-infrared bands (aperture size of 7 kpc) and from the literature,we find that the mean Age of central stellar populations in Spirals with pseudobulges is consistent with that of disky galaxies and is nearly constant against the bulge-to-total ratio (B/T).Paired Spirals have a slightly lower fraction of pure disk galaxies (B/T≤0.1) than their counterparts in the control sample.Compared to SFGs with classical bulges,those with pseudobulges have a higher (>2σ) mean of specific star formation rate (sSFR) enhancement (sSFR_(enh)=0.33±0.07 versus sSFR_(enh)=0.12±0.06) and broader scatter (by~1 dex).The eight SFGs that have the highest sSFR_(enh)in the sample all have pseudobulges.A majority (69%) of paired SFGs with strong enhancement (having sSFR more than5 times the median of the control galaxies) have pseudobulges.The Spitzer data show that the pseudobulges in these galaxies are tightly linked to nuclear/circum-nuclear starbursts.Pseudobulge SFGs in S+S and in S+E pairs have significantly (>3σ) different sSFR enhancement,with the means of sSFR_(enh)=0.45±0.08 and-0.04±0.11respectively.We find a decrease in the sSFR enhancements with the density of the environment for SFGs with pseudobulges.Since a high fraction (5/11) of pseudobulge SFGs in S+E pairs are in rich groups/clusters (loca density N_(1Mpc)≥7),the dense environment might be the cause for their low s SFR_(enh).展开更多
We develop a Python tool to estimate the tail distribution of the number of dark matter halos beyond a mass threshold and in a given volume in a light-cone.The code is based on the extended Press-Schechter model and i...We develop a Python tool to estimate the tail distribution of the number of dark matter halos beyond a mass threshold and in a given volume in a light-cone.The code is based on the extended Press-Schechter model and is computationally efficient,typically taking a few seconds on a personal laptop for a given set of cosmological parameters.The high efficiency of the code allows a quick estimation of the tension between cosmological models and the red candidate massive galaxies released by the James Webb Space Telescope,as well as scanning the theory space with the Markov Chain Monte Carlo method.As an example application,we use the tool to study the cosmological implication of the candidate galaxies presented in Labbéet al.The standard Λcold dark matter(ΛCDM)model is well consistent with the data if the star formation efficiency can reach~0.3 at high redshift.For a low star formation efficiency ε~0.1,theΛCDM model is disfavored at~2σ-3σconfidence level.展开更多
The overabundance of the red and massive candidate galaxies observed by the James Webb Space Telescope(JWST)implies efficient structure formation or large star formation efficiency at high redshift z~10.In the scenari...The overabundance of the red and massive candidate galaxies observed by the James Webb Space Telescope(JWST)implies efficient structure formation or large star formation efficiency at high redshift z~10.In the scenario of a low or moderate star formation efficiency,because massive neutrinos tend to suppress the growth of structure of the universe,the JWST observation tightens the upper bound of the neutrino masses.Assuming A cold dark matter cosmology and a star formation efficiency∈[0.05,0.3](flat prior),we perform joint analyses of Planck+JWST and Planck+BAO+JWST,and obtain improved constraints∑m_(ν)<0.196 eV and ∑m_(ν)+<0.111 eV at 95% confidence level,respectively.Based on the above assumptions,the inverted mass ordering,which implies ∑m_(ν)≥0.1 eV,is excluded by Planck+BAO+JWST at 92.7% confidence level.展开更多
Three mechanisms for an alternative to the Doppler effect as an explanation for the redshift are reviewed. A fourth mechanism is the attenuation of the light as given by the Beer-Lambert law. The average value of the ...Three mechanisms for an alternative to the Doppler effect as an explanation for the redshift are reviewed. A fourth mechanism is the attenuation of the light as given by the Beer-Lambert law. The average value of the Hubble constant is therefore derived by processing the galaxies of the NED-D catalog in which the distances are independent of the redshift. The observed anisotropy of the Hubble constant is reproduced by adopting a rim model, a chord model, and both 2D and 3D Voronoi diagrams.展开更多
This article explores the dead universe theory as a novel interpretation for the origin and evolution of the universe, suggesting that our cosmos may have originated from the remnants of a preceding universe. This per...This article explores the dead universe theory as a novel interpretation for the origin and evolution of the universe, suggesting that our cosmos may have originated from the remnants of a preceding universe. This perspective challenges the conventional Big Bang theory, particularly concerning dark matter, the expansion of the universe, and the interpretation of phenomena such as gravitational waves.展开更多
Great experimental results and observations achieved by Astronomy in the last decades revealed new unexplainable phenomena. Astronomers have conclusive new evidence that a recently discovered “dark galaxy” is, in fa...Great experimental results and observations achieved by Astronomy in the last decades revealed new unexplainable phenomena. Astronomers have conclusive new evidence that a recently discovered “dark galaxy” is, in fact, an object the size of a galaxy, made entirely of dark matter. They found that the speed of the Earth’s rotation varies randomly each day. 115 years ago, the Tunguska Event was observed, and astronomers still do not have an explanation of It. Main results of the present article are: 1) Dark galaxies explained by the spinning of their Dark Matter Cores with the surface speed at equator less than the escape velocity. Their Rotational Fission is not happening. Extrasolar systems do not emerge;2) 21-cm Emission explained by the self-annihilation of Dark Matter particles XIONs (5.3 μeV);3) Sun-Earth-Moon Interaction explained by the influence of the Sun’s and the Moon’s magnetic field on the electrical currents of the charged Geomagma (the 660-km layer), and, as a result, the Earth’s daylength varies;4) Tunguska Event explained by a huge atmospheric explosion of the Superbolide, which was a stable Dark Matter Bubble before entering the Earth’s atmosphere.展开更多
We have investigated the role that different galaxy types have in galaxy-galaxy interactions in compact groups. N-body simulations of 6 galaxies consisting of a differing mixture of galaxy types were run to compare th...We have investigated the role that different galaxy types have in galaxy-galaxy interactions in compact groups. N-body simulations of 6 galaxies consisting of a differing mixture of galaxy types were run to compare the relative importance of galaxy population demographic on evolution. Three different groups with differing galaxy content were tested: all spiral, a single elliptical and 50% elliptical. Tidal interaction strength and duration were recorded to assess the importance of an interaction. A group with an equal number of spiral and elliptical galaxies has some of the longest and strongest interactions with elliptical-elliptical interactions being most significant. These elliptical-elliptical interactions are not dominated by a single large event but consist of multiple interactions. Elliptical galaxies tidally interacting with spiral galaxies, have the next strongest interaction events. For the case when a group only has a single elliptical, the largest magnitude tidal interaction is an elliptical on a spiral. Spirals interact with each other through many small interactions. For a spiral only group, the interactions are the weakest compared to the other group types. These spiral interactions are not dominated by any singular event that might be expected to lead to a merger but are more of an ongoing harassment. These results suggest that within a compact group, early type galaxies will not form via merger out of an assemblage of spiral galaxies but rather that compact groups, in effect form around an early type galaxy.展开更多
The coevolution between supermassive black holes(SMBHs) and their host galaxies has been proposed for more than a decade,albeit with little direct evidence about black hole accretion activities regulating galaxy star ...The coevolution between supermassive black holes(SMBHs) and their host galaxies has been proposed for more than a decade,albeit with little direct evidence about black hole accretion activities regulating galaxy star formation at z> 1.In this paper,we study the lifetimes of X-ray active galactic nuclei(AGNs) in UV-selected red sequence(RS),blue cloud(BC) and green valley(GV) galaxies,finding that AGN accretion activities are most prominent in GV galaxies at z ~1.5-2,compared with RS and BC galaxies.We also compare AGN accretion timescales with typical color transition timescales of UV-selected galaxies.We find that the lifetime of GV galaxies at z~1.5-2 is very close to the typical timescale when the AGNs residing in them stay in the high-accretion-rate mode at these redshifts;for BC galaxies,the consistency between the color transition timescale and the black hole strong accretion lifetime is more likely to happen at lower redshifts(z <1).Our results support the scenario where AGN accretion activities govern UV color transitions of host galaxies,making galaxies and their central SMBHs coevolve with each other.展开更多
We investigate the color gradients of galaxies at 0.5 < z < 1.0, using a sample of ~35 000 galaxies with both spectroscopy from the final data release of the VIMOS Public Extragalactic Redshift Survey(VIPERS), a...We investigate the color gradients of galaxies at 0.5 < z < 1.0, using a sample of ~35 000 galaxies with both spectroscopy from the final data release of the VIMOS Public Extragalactic Redshift Survey(VIPERS), and photometry in ultraviolet/optical/near-infrared bands from the VIPERS-MultiLambda Survey(VIPERS-MLS) and the Canada-France-Hawaii Telescope Legacy Survey(CFHTLS).We estimate rest-frame colors, stellar mass, star formation rate from fitting the Spectral Energy Distribution(SED) for each galaxy, as well as a two-zone color ?(u-r), defined as the difference in rest-frame(u-r) color between the outer and inner region of the galaxy. We find that the two-zone color shows weak or no correlations with all galaxy properties considered except stellar mass. On average, ?(u-r) decreases with increasing stellar mass, indicating relatively red colors in galactic centers of more massive galaxies. We then compare the properties of "red-cored" and "blue-cored" galaxies,defined to have either a negative or a positive ?(u-r) respectively. Although the two types of galaxies show similar distributions in most properties, we find massive red-cored galaxies with M*> 1010.5M⊙to have larger sizes at given stellar mass(thus lower surface mass densities), and less massive red-cored galaxies with M*< 1010.5M⊙to have lower central galaxy fraction. These findings can be understood if one assumes that the star formation process happens from inside out, in the same way as recently emphasized in studies of low-z galaxies. The similarity between the galaxies at intermediate redshifts and those at low redshifts supports the idea that galaxy evolution since z~1 has been mainly driven by secular processes internal to galaxies rather than galaxy mergers or external environment.展开更多
基金the support from the National SKA Program of China No.2020SKA0110102the fund for key programs of Shanghai Astronomical Observatory(Grants E195121009 and E297091002)+1 种基金Shanghai Committee of Science and Technology Grant No.19ZR1466700supported in part by the Natural Science Foundation of China(Grants 12133008,12192220,and 12192223)。
文摘We create mock X-ray observations of hot gas in galaxy clusters with a new extension of the L-Galaxies semianalytic model of galaxy formation,which includes the radial distribution of hot gas in each halo.Based on the model outputs,we first build some mock light cones,then generate mock spectra with the SOXS package and derive the mock images in the light cones.Using the mock data,we simulate mock X-ray spectra for the ROSAT all-sky survey,and compare the mock spectra with the observational results.Then,we consider the design parameters of the HUBS mission and simulate the observation of the halo hot gas for HUBS as an important application of our mock work.We find:(1)our mock data match the observations by current X-ray telescopes.(2)The survey of hot baryons in resolved clusters by HUBS is effective below redshift 0.5,and the observations of the emission lines in point-like sources at z>0.5 by HUBS help us understand the hot baryons in the early universe.(3)By taking advantage of the large simulation box and flexibility in semi-analytic models,our mock X-ray observations provide the opportunity to select targets and observation strategies for forthcoming X-ray facilities.
基金the support of the National Natural Science Foundation of China(Nos.11988101 and 12022306)National Key R&D Program of China(No.2022YFF0503403)+5 种基金Ministry of Science and Technology of China(No.2020SKA0110100)science research grants from the China Manned Space Project(Nos.CMS-CSST-2021-B01 and CMS-CSST-2021-A01)CAS Project for Young Scientists in Basic Research(No.YSBR-062)K.C.Wong Education Foundationprovided by the Alfred P.Sloan Foundationthe U.S.Department of Energy’s Office of Science。
文摘The second moment of the stellar velocity within the effective radius,denoted by σ^(2)_(e),is a crucial quantity in galaxy studies,as it provides insight into galaxy properties and their mass distributions.However,large spectroscopic surveys typically do not measure σ_(e) directly,instead providing σ_(aper),the second moment of the stellar velocity within a fixed fiber aperture.In this paper,we derive an empirical aperture correction formula,given byσ_(aper)/σ_(e)=(R_(aper)/R_(e))^(α),using spatially resolved stellar kinematics extracted from approximately 10,000 Sloan Digital Sky Survey-Mapping Nearby Galaxies at Apache Point Observatory integral field unit observations.Our analysis reveals a strong dependence ofαon the r-band absolute magnitude M_(r),g-i color,and Sérsic index nSer,whereαvalues are lower for brighter,redder galaxies with higher Sérsic indices.Our results demonstrate that the aperture correction derived from previous literature on early-type galaxies cannot be applied to predict the aperture corrections for galaxies with intermediate Sérsic indices.We provide a lookup table ofαvalues for different galaxy types,with parameters in the ranges of-18>M_(r)>-24,0.4<g-i<1.6,and 0<n_(Ser)<8.A Python script is provided to obtain the correction factors from the lookup table.
基金support from the National Key Research and Development Program of China(2022SKA0130100)the National Natural Science Foundation of China (grant No. 12041306)+1 种基金supported by national funds through Fundacao para a Ciência e a Tecnologia (FCT)the Centro de Astrofísica da Universidade do Porto (CAUP)。
文摘We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9(z = 0.005)(hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy(TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g-r color of 0.23 mag, irregular optical morphology and high-metallicity(12 +log(O/H) = 8.68 ± 0.14), making it an interesting galaxy to study in more detail. We find J2306 to be an H I rich galaxy with a large extended, unperturbed rotating H I disk. Using our H I data we estimated its dynamical mass and found the galaxy to be dark matter(DM) dominated within its H I radius. The quantity of DM, inferred from its dynamical mass, appears to rule out J2306 as an evolved TDG. A wide area environment search reveals J2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the H I morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity.Further detailed optical spectroscopic observations of J2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment.
基金partially supported by the National SKA Program of China(grant No.2022SKA0120103)the National Natural Science Foundation of China(Nos.11988101 and 11833009,12073036)+2 种基金support from the science research grants from the China Manned Space Project(CMS-CSST-2021-A01,CMS-CSST-2021-B01)the financial support from the National Key R&D Program of China(No.2021YFA1600401 and 2021YFA1600400)the International Partnership Program of Chinese Academy of Sciences,grant No.114A11KYSB20170044。
文摘The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(La GRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known La GRLs,we confirm the correlation between radio power P_(1.4GHz)and stellar mass M_(*)of host galaxies.Most(25/35)La GRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P_(1.4GHz)-M_(*)relation,and the galaxy color,indicating that bluer galaxies at a fixed M_(*)tend to host more powerful radio lobes.Furthermore,the majority(31/36)of La GRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.
文摘The structural parameters of a galaxy can be used to gain insight into its formation and evolution history.In this paper,we strive to compare the Milky Way’s structural parameters to other,primarily edge-on,spiral galaxies in order to determine how our Galaxy measures up to the Local Universe.For our comparison,we use the galaxy structural parameters gathered from a variety of literature sources in the optical and near-infrared wave bands.We compare the scale length,scale height,and disk flatness for both the thin and thick disks,the thick-to-thin disk mass ratio,the bulge-to-total luminosity ratio,and the mean pitch angle of the Milky Way’s spiral arms to those in other galaxies.We conclude that many of the Milky Way’s structural parameters are largely ordinary and typical of spiral galaxies in the Local Universe,though the Galaxy’s thick disk appears to be appreciably thinner and less extended than expected from zoom-in cosmological simulations of Milky Way-mass galaxies with a significant contribution of galaxy mergers involving satellite galaxies.
基金supported by the Joint Research Fund in AstronomyNational Natural Science Foundation of China(NSFC,grant No.U1931134)+1 种基金the Natural Science Foundation of Hebei,A2020202001the Natural Science Foundation of Tianjin Municipality,22JCYBJC00410。
文摘This study introduces a novel convolutional neural network,the WISE Galaxy Classification Network(WGC),for classifying spiral and elliptical galaxies using Wide-field Infrared Survey Explorer(WISE)images.WGC attains an accuracy of 89.03%,surpassing the combined use of K-means or SVM with the Color-Color method in more accurately identifying galaxy morphologies.The enhanced variant,WGC_mag,integrates magnitude parameters with image features,further boosting the accuracy to 89.89%.The research also delves into the criteria for galaxy classification,discovering that WGC primarily categorizes dust-rich images as elliptical galaxies,corresponding to their lower star formation rates,and classifies less dusty images as spiral galaxies.The paper explores the consistency and complementarity of WISE infrared images with SDSS optical images in galaxy morphology classification.The SDSS Galaxy Classification Network(SGC),trained on SDSS images,achieved an accuracy of 94.64%.The accuracy reached 99.30% when predictions from SGC and WGC were consistent.Leveraging the complementarity of features in WISE and SDSS images,a novel variant of a classifier,namely the Multi-band Galaxy Morphology Integrated Classifier,has been developed.This classifier elevates the overall prediction accuracy to 95.39%.Lastly,the versatility of WGC was validated in other data sets.On the HyperLEDA data set,the distinction between elliptical galaxies and Sc,Scd and Sd spiral galaxies was most pronounced,achieving an accuracy of 90%,surpassing the classification results of the Galaxy Zoo 2 labeled WISE data set.This research not only demonstrates the effectiveness of WISE images in galaxy morphology classification but also represents an attempt to integrate multi-band astronomical data to enhance understanding of galaxy structures and evolution.
基金supported by the Natural Science Research Programs of Jiangsu Province University(23KJB160001 and 23KJB140004)by the support of the scientific research fund of Jiangsu Second Normal University(927801/032)+1 种基金supported by the Hebei Natural Science Foundation(grant No.A2022408002)the Fundamental Research Funds for the Universities in Hebei Province(grant No.JYQ202003)。
文摘How galaxies assemble masses through their own star formation or interaction with the external environment is still an important topic in the field of galaxy formation and evolution.We use Value Added Catalogs with galaxy features that are spatially and temporally resolved from Sloan Digital Sky Survey Data Release 17 to investigate the mass growth histories of early-type galaxies(ETGs)and late-type galaxies(LTGs).We find that the mass growth of ETGs is earlier than that of LTGs for massive galaxies(M_(*)>10^(10)M_⊙),while low-mass(M_(*)≤10^(10)M_⊙)ETGs have statistically similar mass assembly histories as low-mass LTGs.The stellar metallicity of all massive galaxies shows a negative gradient and basically does not change with time.However,in low-mass galaxies,the stellar metallicity gradient of elliptical galaxies is negative,and the stellar metallicity gradient of lenticular and spiral galaxies evolves from positive to negative.ETGs are not all in a high-density environment,but exhibit mass dependence.As the tidal strength increases,the star formation rate of low-mass ETGs rapidly decreases.These results support a picture where massive galaxies exhibit inside-out quenching mode,while low-mass galaxies show outside-in quenching mode.Environmental effects play an important role in regulating the mass assembly histories of low-mass ETGs.
基金supported by the National Key R&D Program of China (grant No.2022YFA1602901)support of the National Natural Science Foundation of China(NSFC) grant Nos. 12090040, 12090041, and 12003043+5 种基金supported by the Youth Innovation Promotion AssociationCAS (No. 2020057)the science research grants of CSST from the China Manned Space Projectsupport of the NSFC grant Nos.11733006 and U1931109supported by the Strategic Priority Research Program of the Chinese Academy of Sciences,Grant No. XDB0550100partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences。
文摘We present a study of low surface brightness galaxies(LSBGs) selected by fitting the images for all the galaxies inα.40 SDSS DR7 sample with two kinds of single-component models and two kinds of two-component models(disk+bulge):single exponential,single sersic,exponential+deVaucular(exp+deV),and exponential+sérsic(exp+ser).Under the criteria of the B band disk central surface brightness μ_(0,disk)(B)≥22.5 mag arcsec^(-2) and the axis ratio b/a> 0.3,we selected four none-edge-on LSBG samples from each of the models which contain 1105,1038,207,and 75 galaxies,respectively.There are 756 galaxies in common between LSBGs selected by exponential and sersic models,corresponding to 68.42% of LSBGs selected by the exponential model and 72.83% of LSBGs selected by the sersic model,the rest of the discrepancy is due to the difference in obtaining μ_(0) between the exponential and sersic models.Based on the fitting,in the range of 0.5≤n≤1.5,the relation of μ_(0) from two models can be written as μ_(0,sérsic)-μ_(0,exp)=-1.34(n-1).The LSBGs selected by disk+bulge models(LSBG_(2)comps) are more massive than LSBGs selected by single-component models(LSBG_1comp),and also show a larger disk component.Though the bulges in the majority of our LSBG_(2)comps are not prominent,more than 60% of our LSBG_(2)comps will not be selected if we adopt a single-component model only.We also identified 31 giant low surface brightness galaxies(gLSBGs) from LSBG_(2)comps.They are located at the same region in the color-magnitude diagram as other gLSBGs.After we compared different criteria of gLSBGs selection,we find that for gas-rich LSBGs,M_(*)> 10^(10)M_⊙ is the best to distinguish between gLSBGs and normal LSBGs with bulge.
基金supported by National Key R&D Program of China(Nos.2019YFA0405501 and 2022YFF0503402)the National Natural Science Foundation of China(NSFC,Nos.12233005 and 12041302)+6 种基金support from the Natural Science Foundation of Shanghai(Project Number:22ZR1473000)the Program of Shanghai Academic Research Leader(No.22XD1404200)supports from the CAS Pioneer Hundred Talents ProgramUSTC Research Funds of the Double First-Class Initiativethe NSFC grant 12273037the NSFC grants 12033004,12333003support from the NSFC through grants 12273091 and U2031139。
文摘The star-forming clumps in star-bursting dwarf galaxies provide valuable insights into understanding the evolution of dwarf galaxies.In this paper,we focus on five star-bursting dwarf galaxies featuring off-centered clumps in the Mapping Nearby Galaxies at Apache Point Observatory survey.Using the stellar population synthesis software Fitting Analysis using Differential evolution Optimization,we obtain the spatially resolved distribution of the star formation history,which allows us to construct the g-band images of the five galaxies at different ages.These images can help us to probe the evolution of the morphological structures of these galaxies.While images of a stellar population older than 1 Gyr are typically smooth,images of a stellar population younger than 1 Gyr reveal significant clumps,including multiple clumps which appear at different locations and even different ages.To study the evolutionary connections of these five galaxies to other dwarf galaxies before their star-forming clumps appear,we construct the images of the stellar populations older than three age nodes,and define them to be the images of the"host"galaxies.We find that the properties such as the central surface brightness and the effective radii of the hosts of the five galaxies are in between those of dwarf ellipticals(dEs)and dwarf irregulars(dIrrs),with two clearly more similar to dEs and one more similar to dIrrs.Among the five galaxies,8257-3704 is particularly interesting,as it shows a previous starburst event that is not quite visible from its gri image,but only visible from images of the stellar population at a few hundred million years.The star-forming clump associated with this event may have appeared at around 600 Myr ago and disappeared at around 40 Myr ago.
基金supported by the National Natural Science Foundation of China(NSFC)No.11873055 and No.11933003sponsored(in part)by the Chinese Academy of Sciences(CAS)through a grant to the CAS South America Center for Astronomy(CASSACA)+4 种基金support from project PID2020-114414GB-100,financed by MCIN/AEI/10.13039/501100011033the Junta de Andaluciaía(Spain)grant FQM108support by the National Key R&D Program of China No.2017YFA0402600the National Natural Science Foundation of China(NSFC)grant Nos.11890692,12133008,and 12221003China Manned Space Project No.CMS-CSST2021-A04。
文摘We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic index n<2) in a loca close major-merger galaxy pair sample (H-KPAIR).With data from new aperture photometries in the optical and near-infrared bands (aperture size of 7 kpc) and from the literature,we find that the mean Age of central stellar populations in Spirals with pseudobulges is consistent with that of disky galaxies and is nearly constant against the bulge-to-total ratio (B/T).Paired Spirals have a slightly lower fraction of pure disk galaxies (B/T≤0.1) than their counterparts in the control sample.Compared to SFGs with classical bulges,those with pseudobulges have a higher (>2σ) mean of specific star formation rate (sSFR) enhancement (sSFR_(enh)=0.33±0.07 versus sSFR_(enh)=0.12±0.06) and broader scatter (by~1 dex).The eight SFGs that have the highest sSFR_(enh)in the sample all have pseudobulges.A majority (69%) of paired SFGs with strong enhancement (having sSFR more than5 times the median of the control galaxies) have pseudobulges.The Spitzer data show that the pseudobulges in these galaxies are tightly linked to nuclear/circum-nuclear starbursts.Pseudobulge SFGs in S+S and in S+E pairs have significantly (>3σ) different sSFR enhancement,with the means of sSFR_(enh)=0.45±0.08 and-0.04±0.11respectively.We find a decrease in the sSFR enhancements with the density of the environment for SFGs with pseudobulges.Since a high fraction (5/11) of pseudobulge SFGs in S+E pairs are in rich groups/clusters (loca density N_(1Mpc)≥7),the dense environment might be the cause for their low s SFR_(enh).
基金supported by the National Key R&D Program of China(grant No.2020YFC2201600)the National Natural Science Foundation of China(NSFC,grant No.12073088)the National SKA Program of China(grant No.2020SKA0110402)。
文摘We develop a Python tool to estimate the tail distribution of the number of dark matter halos beyond a mass threshold and in a given volume in a light-cone.The code is based on the extended Press-Schechter model and is computationally efficient,typically taking a few seconds on a personal laptop for a given set of cosmological parameters.The high efficiency of the code allows a quick estimation of the tension between cosmological models and the red candidate massive galaxies released by the James Webb Space Telescope,as well as scanning the theory space with the Markov Chain Monte Carlo method.As an example application,we use the tool to study the cosmological implication of the candidate galaxies presented in Labbéet al.The standard Λcold dark matter(ΛCDM)model is well consistent with the data if the star formation efficiency can reach~0.3 at high redshift.For a low star formation efficiency ε~0.1,theΛCDM model is disfavored at~2σ-3σconfidence level.
基金supported by the National SKA Program of China No.2020SKA0110402the National Natural Science Foundationof China(NSFC)under grant No.12073088the National Key R&D Program of China(grant No.2020YFC2201600)。
文摘The overabundance of the red and massive candidate galaxies observed by the James Webb Space Telescope(JWST)implies efficient structure formation or large star formation efficiency at high redshift z~10.In the scenario of a low or moderate star formation efficiency,because massive neutrinos tend to suppress the growth of structure of the universe,the JWST observation tightens the upper bound of the neutrino masses.Assuming A cold dark matter cosmology and a star formation efficiency∈[0.05,0.3](flat prior),we perform joint analyses of Planck+JWST and Planck+BAO+JWST,and obtain improved constraints∑m_(ν)<0.196 eV and ∑m_(ν)+<0.111 eV at 95% confidence level,respectively.Based on the above assumptions,the inverted mass ordering,which implies ∑m_(ν)≥0.1 eV,is excluded by Planck+BAO+JWST at 92.7% confidence level.
文摘Three mechanisms for an alternative to the Doppler effect as an explanation for the redshift are reviewed. A fourth mechanism is the attenuation of the light as given by the Beer-Lambert law. The average value of the Hubble constant is therefore derived by processing the galaxies of the NED-D catalog in which the distances are independent of the redshift. The observed anisotropy of the Hubble constant is reproduced by adopting a rim model, a chord model, and both 2D and 3D Voronoi diagrams.
文摘This article explores the dead universe theory as a novel interpretation for the origin and evolution of the universe, suggesting that our cosmos may have originated from the remnants of a preceding universe. This perspective challenges the conventional Big Bang theory, particularly concerning dark matter, the expansion of the universe, and the interpretation of phenomena such as gravitational waves.
文摘Great experimental results and observations achieved by Astronomy in the last decades revealed new unexplainable phenomena. Astronomers have conclusive new evidence that a recently discovered “dark galaxy” is, in fact, an object the size of a galaxy, made entirely of dark matter. They found that the speed of the Earth’s rotation varies randomly each day. 115 years ago, the Tunguska Event was observed, and astronomers still do not have an explanation of It. Main results of the present article are: 1) Dark galaxies explained by the spinning of their Dark Matter Cores with the surface speed at equator less than the escape velocity. Their Rotational Fission is not happening. Extrasolar systems do not emerge;2) 21-cm Emission explained by the self-annihilation of Dark Matter particles XIONs (5.3 μeV);3) Sun-Earth-Moon Interaction explained by the influence of the Sun’s and the Moon’s magnetic field on the electrical currents of the charged Geomagma (the 660-km layer), and, as a result, the Earth’s daylength varies;4) Tunguska Event explained by a huge atmospheric explosion of the Superbolide, which was a stable Dark Matter Bubble before entering the Earth’s atmosphere.
文摘We have investigated the role that different galaxy types have in galaxy-galaxy interactions in compact groups. N-body simulations of 6 galaxies consisting of a differing mixture of galaxy types were run to compare the relative importance of galaxy population demographic on evolution. Three different groups with differing galaxy content were tested: all spiral, a single elliptical and 50% elliptical. Tidal interaction strength and duration were recorded to assess the importance of an interaction. A group with an equal number of spiral and elliptical galaxies has some of the longest and strongest interactions with elliptical-elliptical interactions being most significant. These elliptical-elliptical interactions are not dominated by a single large event but consist of multiple interactions. Elliptical galaxies tidally interacting with spiral galaxies, have the next strongest interaction events. For the case when a group only has a single elliptical, the largest magnitude tidal interaction is an elliptical on a spiral. Spirals interact with each other through many small interactions. For a spiral only group, the interactions are the weakest compared to the other group types. These spiral interactions are not dominated by any singular event that might be expected to lead to a merger but are more of an ongoing harassment. These results suggest that within a compact group, early type galaxies will not form via merger out of an assemblage of spiral galaxies but rather that compact groups, in effect form around an early type galaxy.
基金support from the National Natural Science Foundation of China (grant Nos. 12025303, 11890693,11421303 and 12003031)the CAS Frontier Science Key Research Program (QYZDJ-SSW-SLH006)+2 种基金the K.C. Wong Education Foundationthe science research grants from the China Manned Space Project with No. CMS-CSST-2021-A06support from the Chinese Academy of Sciences President’s International Fellowship Initiative (grant No. 2019PM0020)。
文摘The coevolution between supermassive black holes(SMBHs) and their host galaxies has been proposed for more than a decade,albeit with little direct evidence about black hole accretion activities regulating galaxy star formation at z> 1.In this paper,we study the lifetimes of X-ray active galactic nuclei(AGNs) in UV-selected red sequence(RS),blue cloud(BC) and green valley(GV) galaxies,finding that AGN accretion activities are most prominent in GV galaxies at z ~1.5-2,compared with RS and BC galaxies.We also compare AGN accretion timescales with typical color transition timescales of UV-selected galaxies.We find that the lifetime of GV galaxies at z~1.5-2 is very close to the typical timescale when the AGNs residing in them stay in the high-accretion-rate mode at these redshifts;for BC galaxies,the consistency between the color transition timescale and the black hole strong accretion lifetime is more likely to happen at lower redshifts(z <1).Our results support the scenario where AGN accretion activities govern UV color transitions of host galaxies,making galaxies and their central SMBHs coevolve with each other.
基金supported by the National Key Basic Research Program of China(No.2015CB857004)the National Natural Science Foundation of China(Grant Nos.11173045,11233005,11325314 and 11320101002)
文摘We investigate the color gradients of galaxies at 0.5 < z < 1.0, using a sample of ~35 000 galaxies with both spectroscopy from the final data release of the VIMOS Public Extragalactic Redshift Survey(VIPERS), and photometry in ultraviolet/optical/near-infrared bands from the VIPERS-MultiLambda Survey(VIPERS-MLS) and the Canada-France-Hawaii Telescope Legacy Survey(CFHTLS).We estimate rest-frame colors, stellar mass, star formation rate from fitting the Spectral Energy Distribution(SED) for each galaxy, as well as a two-zone color ?(u-r), defined as the difference in rest-frame(u-r) color between the outer and inner region of the galaxy. We find that the two-zone color shows weak or no correlations with all galaxy properties considered except stellar mass. On average, ?(u-r) decreases with increasing stellar mass, indicating relatively red colors in galactic centers of more massive galaxies. We then compare the properties of "red-cored" and "blue-cored" galaxies,defined to have either a negative or a positive ?(u-r) respectively. Although the two types of galaxies show similar distributions in most properties, we find massive red-cored galaxies with M*> 1010.5M⊙to have larger sizes at given stellar mass(thus lower surface mass densities), and less massive red-cored galaxies with M*< 1010.5M⊙to have lower central galaxy fraction. These findings can be understood if one assumes that the star formation process happens from inside out, in the same way as recently emphasized in studies of low-z galaxies. The similarity between the galaxies at intermediate redshifts and those at low redshifts supports the idea that galaxy evolution since z~1 has been mainly driven by secular processes internal to galaxies rather than galaxy mergers or external environment.