According to the standard“inside-out”galaxy formation scenario,galaxies first form a dense core and then gradually assemble their outskirts.This implies that galaxies with similar central stellar mass densities migh...According to the standard“inside-out”galaxy formation scenario,galaxies first form a dense core and then gradually assemble their outskirts.This implies that galaxies with similar central stellar mass densities might have evolutionary links.We use the UVJ color-color diagram to select quiescent galaxies in the redshift interval from 0.5 to 2.5 and classify them into different subsamples based on their central stellar mass densities,stellar mass,morphological type and redshift.We then infer the intrinsic axis ratiosμ_(B/A) andμC/A of different subsamples based on the apparent axis ratio q distributions,where A,B,and C refer to,respectively,the major,intermediate and minor axis of a triaxial ellipsoidal model.We find that(1)massive quiescent galaxies have typical intrinsic shapes similarly close to thick oblate structures,withμ_(B/A)0.9,regardless of stellar mass,redshift,or central stellar mass densities,and(2)galaxies at higher redshift are systematically thinner than their lower-redshift counterparts,and(3)when splitting the sample into early type and late type with Sérsic indices,ETGs at higher redshift are slightly more prolate(smaller averageμ_(B/A))than those at lower redshift.Minor mergers of galaxies may have played important roles in the structural evolution of quiescent galaxies found in this work.展开更多
This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting ...This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting prominent[OⅢ]emission lines,of which 351 quasars have Category 1 MgⅡabsorption lines(4365≤υ_(r)≤10,000 km s^(-)1)and 518 quasars have Category 2 MgⅡabsorption lines(610≤υ_(r)≤4365 km s-1).Subsequently,we quantify the asymmetries of[OⅢ]emission lines using the velocity offsetδv,and find that the detection rates of Category 1 MgⅡabsorption lines(predominantly intervening absorbers)show no correlation with the blueshifted asymmetries of[OⅢ]emission lines,whereas the detection rates of Category 2 MgⅡabsorption lines(primarily outflow and intervening absorbers)increase with risingδ_(v).Finally,we discuss the results from two perspectives:quasar evolutionary stages and acceleration mechanisms driven by radiation pressure.展开更多
This is the second paper in a series that utilizes integral field spectroscopy from MaNGA,NUV imaging from Swift/UVOT,and NIR imaging from 2MASS to investigate dust attenuation properties on kpc scales in nearby galax...This is the second paper in a series that utilizes integral field spectroscopy from MaNGA,NUV imaging from Swift/UVOT,and NIR imaging from 2MASS to investigate dust attenuation properties on kpc scales in nearby galaxies.We apply the method developed in our previous work to the updated SwiM_v4.2 catalog,and measure the optical attenuation curve and the attenuation in three NUV bands for 2487 spaxels selected from 91 galaxies with S/N> 20 and AV> 0.25.We classify all spaxels into two subsets:star-forming(SF) regions and non-SF regions.We explore the correlations of optical opacity(A_(V)) and the optical and NUV slopes of the attenuation curves(A_(B)/A_(V) and A_(w2)/A_(w1)) with a broad range of stellar population and emission-line properties,including specific surface brightness of Hα emission(∑_(Hα)/∑_(*)),stellar age,stellar and gas-phase metallicity,and diagnostics of recent star formation history.Overall,when comparing SF and non-SF regions,we find that A_(V) and A_(B)/A_(V) exhibit similar correlations with all the stellar population and emission-line properties considered,while the NUV slopes in SF regions tend to be flatter than those in non-SF regions.The NUV slope A_(w2)/A_(w1) exhibits an anti-correlation with ∑_(Hα)/∑_(*),a trend that is primarily driven by the positive correlation between A_(w2)/A_(w1) and ∑_(*).The NUV slope flattens in SF regions that contain young stellar populations and have experienced recent star formation,but it shows no obvious dependence on stellar or gas-phase metallicity.The spatially resolved dust attenuation properties exhibit no clear correlations with the inclination of host galaxies or the galactocentric distance of the regions.This finding reinforces the conclusion from Paper I that dust attenuation is primarily regulated by local processes on kpc scales or smaller,rather than by global processes at galactic scales.展开更多
Based on the updated M giant star catalog selected from Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR9,we identify substructures within the integrals-of-motion space through the Friends-of-Friends clust...Based on the updated M giant star catalog selected from Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR9,we identify substructures within the integrals-of-motion space through the Friends-of-Friends clustering algorithm.We obtain members belonging to several known substructures:the Sagittarius stream,Galactic Anticenter Substructure(GASS),Gaia-Enceladus-Sausage(GES),Splash,and the high-αdisk.Furthermore,we also identify two groups which cannot be clearly associated with previously known substructures.Our findings confirm the existence of metal-rich constituents within the GES,representing newly formed stars that originated from the metal-enriched gas delivered during the GES merger event and subsequently evolved.Additionally,this study further expands the sample of GASS,high-αdisk,and Splash stars.Analysis of these metal-rich M giant stars as members of the GES,Splash,and high-αdisk components supports an evolution scenario for the early Milky Way,as proposed by previous studies.In this scenario,stars initially formed in a high-α primordial disk were dynamically heated by the massive accretion event(GES).This process redistributed stellar orbits,creating the Splash population,while the undisturbed portion of the primordial disk persisted as the present-day high-αdisk component.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
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
Superthin galaxies are observed to have stellar disks with extremely small minor-to-major axis ratios.In this work,we investigate the formation of superthin galaxies in the TNG100 simulation.We trace the merger histor...Superthin galaxies are observed to have stellar disks with extremely small minor-to-major axis ratios.In this work,we investigate the formation of superthin galaxies in the TNG100 simulation.We trace the merger history and investigate the evolution of galaxy properties of a selected sample of superthin galaxies and a control sample of galaxies that share the same joint probability distribution in the stellar-mass and color diagram.Through making comparisons between the two galaxy samples,we find that present-day superthin galaxies had similar morphologies as the control sample counterparts at higher redshifts,but have developed extended flat“superthin”morphologies since z~1.During this latter evolution stage,superthin galaxies undergo an overwhelmingly higher frequency of prograde mergers(with orbit-spin angleθ_(orb)≤40°).Accordingly the spins of their dark matter halos have grown significantly and become noticeably higher than those of their normal disk counterparts.This further results in the buildup of their stellar disks at larger distances much beyond the regimes of normal disk galaxies.We also discuss the formation scenario of those superthin galaxies that live in larger dark matter halos as satellite galaxies therein.展开更多
We report a new high-sensitivity HⅠmapping observation of the NGC 5055 galaxy group over an area of 1°.5×0°.75 with the Five-hundred-meter Aperture Spherical radio Telescope(FAST).Our observation revea...We report a new high-sensitivity HⅠmapping observation of the NGC 5055 galaxy group over an area of 1°.5×0°.75 with the Five-hundred-meter Aperture Spherical radio Telescope(FAST).Our observation reveals that the warped HⅠdisk of NGC 5055 is more extended than what was previously observed by WSRT,out to239(61.7 kpc).The total HⅠmass of NGC 5055 is determined to be~1.1×10^(10)M_Θ.We identified three HⅠclouds with HⅠmasses of the order of~10^(7)M_Θat the southeastern edge of the HⅠdisk,as well as a candidate high-velocity cloud with an HⅠmass of(1.2±0.5)×10^(6)M_Θto the north of NGC 5055.The HⅠcontent of UGCA337 is robustly detected for the first time by the FAST observations.It has a narrow HⅠlinewidth of W_(50)=17.4±3.8 km s^(-1)with a total HⅠmass of(3.5±0.3)×10^(6)M_Θ.Comparing the gas content and g-r color of UGCA 337 with typical low-mass dwarf galaxies,UGCA 337 appears relatively gas-poor despite its blue color.This suggests that UGCA 337 may have undergone gas stripping in the past.We also analyzed the possible origin of the diffuse HⅠclouds located at the outskirts of NGC 5055,and speculate that they might be the remnant features of a merger event in the past.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
Compact groups have high galaxy densities and low velocity dispersions,and their group members have experienced numerous and frequent interactions during their lifetimes.They provide a unique environment to study the ...Compact groups have high galaxy densities and low velocity dispersions,and their group members have experienced numerous and frequent interactions during their lifetimes.They provide a unique environment to study the evolution of galaxies.We examined the galaxies types and H I contents in groups to make a study on the galaxy evolution in compact groups.We used the group crossing time as an age indicator for galaxy groups.Our sample is derived from the Hickson Compact Group catalog.We obtained group morphology data from the Hyper-Leda database and the IR classification based on Wide-Field Infrared Survey Explorer fluxes from Zucker et al.By cross-matching the latest released ALFALFA 100%H I source catalog with supplement by data found in literature,we obtained 40 galaxy groups with H I data available.We confirmed that the weak correlation between H I mass fraction and group crossing time found by Ai&Zhu in SDSS groups also exists in compact groups.We also found that the group spiral galaxy fraction is correlated with the group crossing time,but the actively star-forming galaxy fraction is not correlated with the group crossing time.These results seem to fit with the hypothesis that the sequential acquisition of neighbors from surrounding larger-scale structures has affected the morphology transition and star formation efficiency in compact groups.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 use the recently discovered simple photometric parameter Central Intensity Ratio(CIR)determined for a sample of 57 nearby(z<0.02)Seyfert galaxies to explore the central features of galaxies and their possible co...We use the recently discovered simple photometric parameter Central Intensity Ratio(CIR)determined for a sample of 57 nearby(z<0.02)Seyfert galaxies to explore the central features of galaxies and their possible connection with galaxy evolution.The sample of galaxies shows strong anti-correlation between CIR and mass of their central supermassive black holes(SMBHs).The SMBH masses of ellipticals are systematically higher for a given CIR value than those for lenticulars and spirals in the sample.However,the correlation between CIR and central velocity dispersion is weak.CIR appears less influenced by the excess flux produced by the central engine in these galaxies,when compared to spectroscopic parameters like velocity dispersion and OⅣflux,and proves to be a fast and reliable tool for estimating central SMBH mass.展开更多
Based on a large sample of massive(M* 1010 M⊙) compact galaxies at 1.0 < z < 3.0 in five 3 D-HST/CANDELS fields, we quantify the fractional abundance and comoving number density of massive compact galaxies as a...Based on a large sample of massive(M* 1010 M⊙) compact galaxies at 1.0 < z < 3.0 in five 3 D-HST/CANDELS fields, we quantify the fractional abundance and comoving number density of massive compact galaxies as a function of redshift. The samples of compact quiescent galaxies(cQGs) and compact star-forming galaxies(cSFGs) are constructed by various selection criteria of compact galaxies in the literature, and the effect of compactness definition on abundance estimate has proven to be remarkable,particularly for the cQGs and cSFGs at high redshifts. Regardless of the compactness criteria adopted,their overall redshift evolutions of fractional abundance and number density are found to be rather similar.Large samples of the cQGs exhibit a sustained increase in number density from z ~ 3 to 2 and a plateau at 1 < z < 2. For massive cSFGs, a plateau in the number density at 2 < z < 3 can be found, as well as a continuous drop from z ~ 2 to 1. The evolutionary trends of the cQG and cSFG abundances support the scenario that the cSFGs at z≥ 2 may have been rapidly quenched into quiescent phase via violent dissipational processes, such as major merger and disk instabilities. The rarity of the cSFGs at lower redshifts(z < 1) can be interpreted by the decrease of gas reservoirs in dark matter halos and the consequent low efficiency of gas-rich dissipation.展开更多
The observational data of high redshift galaxies become increasingly abundant,especially since the operation of the James Webb Space Telescope,which allows us to verify and optimize the galaxy formation model at high ...The observational data of high redshift galaxies become increasingly abundant,especially since the operation of the James Webb Space Telescope,which allows us to verify and optimize the galaxy formation model at high redshifts.In this work,we investigate the merging history of massive galaxies at 3<z<6 using a well-developed semi-analytic galaxy formation catalog.We find that the major merger rate increases with redshift up to 3 and then flattens.The fraction of wet mergers,during which the sum of the cold gas mass is higher than the sum of the stellar mass in two merging galaxies,also increases from~34%at z=0 to 96%at z=3.Interestingly,almost all major mergers are wet at z>3.This can be attributed to the high fraction(>50%)of cold gas at z>3.In addition,we study some special systems of massive merging galaxies at 3<z<6,including the massive gas-rich major merging systems and extreme dense proto-clusters,and investigate the supermassive black hole-dark matter halo mass relation and dual active galactic nuclei.We find that the galaxy formation model reproduces the incidence of those observed massive galaxies,but fails to reproduce the relation between the supermassive black hole mass and the dark matter halo mass at z~6.The latter requires more careful estimates of the supermassive black hole masses observationally.Otherwise,it could suggest modifications of the modeling of the supermassive black hole growth at high redshifts.展开更多
Major interactions are known to trigger star formation in galaxies and alter their color.We study the major interactions in filaments and sheets using SDSS data to understand the influence of large-scale environments ...Major interactions are known to trigger star formation in galaxies and alter their color.We study the major interactions in filaments and sheets using SDSS data to understand the influence of large-scale environments on galaxy interactions.We identify the galaxies in filaments and sheets using the local dimension and also find the major pairs residing in these environments.The star formation rate(SFR) and color of the interacting galaxies as a function of pair separation are separately analyzed in filaments and sheets.The analysis is repeated for three volume limited samples covering different magnitude ranges.The major pairs residing in the filaments show a significantly higher SFR and bluer color than those residing in the sheets up to the projected pair separation of~50 kpc.We observe a complete reversal of this behavior for both the SFR and color of the galaxy pairs having a projected separation larger than 50 kpc.Some earlier studies report that the galaxy pairs align with the filament axis.Such alignment inside filaments indicates anisotropic accretion that may cause these differences.We do not observe these trends in the brighter galaxy samples.The pairs in filaments and sheets from the brighter galaxy samples trace relatively denser regions in these environments.The absence of these trends in the brighter samples may be explained by the dominant effect of the local density over the effects of the large-scale environment.展开更多
Based on the method proposed by Kong et al. and on the multi-color spectrophotometry by Ma et al., we estimate the metallicities of 16 old star clusters in the nearby spiral galaxy M33, ten of which are halo globula...Based on the method proposed by Kong et al. and on the multi-color spectrophotometry by Ma et al., we estimate the metallicities of 16 old star clusters in the nearby spiral galaxy M33, ten of which are halo globular clusters. These old clusters are all metal poor, the range of metallicity ([Fe/H]) is from-0.14 to-2.12. In general, our results are consistent with those derived by other methods, such as integrated spectra and photometry, and our study confirms the reliability of the method of Kong et al.展开更多
基金support from the National Key Research and Development Program of China (grant No.2023YFA1608100)from the National Natural Science Foundation of China(NSFC,grant Nos.12122303 and 11973039)+2 种基金supported by the China Manned Space Project (grant Nos.CMSCSST-2021-B02 and CMS-CSST-2021-A07)support from the CAS Pioneer Hundred Talents Programthe Cyrus Chun Ying Tang Foundations
文摘According to the standard“inside-out”galaxy formation scenario,galaxies first form a dense core and then gradually assemble their outskirts.This implies that galaxies with similar central stellar mass densities might have evolutionary links.We use the UVJ color-color diagram to select quiescent galaxies in the redshift interval from 0.5 to 2.5 and classify them into different subsamples based on their central stellar mass densities,stellar mass,morphological type and redshift.We then infer the intrinsic axis ratiosμ_(B/A) andμC/A of different subsamples based on the apparent axis ratio q distributions,where A,B,and C refer to,respectively,the major,intermediate and minor axis of a triaxial ellipsoidal model.We find that(1)massive quiescent galaxies have typical intrinsic shapes similarly close to thick oblate structures,withμ_(B/A)0.9,regardless of stellar mass,redshift,or central stellar mass densities,and(2)galaxies at higher redshift are systematically thinner than their lower-redshift counterparts,and(3)when splitting the sample into early type and late type with Sérsic indices,ETGs at higher redshift are slightly more prolate(smaller averageμ_(B/A))than those at lower redshift.Minor mergers of galaxies may have played important roles in the structural evolution of quiescent galaxies found in this work.
基金supported by the Scientific Research Project of Guangxi Minzu University(2023KJQD07)Guangxi Natural Science Foundation(2025GXNSFBA069287)+2 种基金the Guangxi Natural Science Foundation(2024GXNSFDA010069,2019GXNSFFA245008)the National Natural Science Foundation of China(12073007)the Scientific Research Project of Guangxi University for Nationalities(2018KJQD01)。
文摘This study investigates the relationship between the detection rates of MgⅡabsorption lines and the asymmetries of[OⅢ]emission lines.We first select 21,364 quasars from the Sloan Digital Sky Survey DR12Q exhibiting prominent[OⅢ]emission lines,of which 351 quasars have Category 1 MgⅡabsorption lines(4365≤υ_(r)≤10,000 km s^(-)1)and 518 quasars have Category 2 MgⅡabsorption lines(610≤υ_(r)≤4365 km s-1).Subsequently,we quantify the asymmetries of[OⅢ]emission lines using the velocity offsetδv,and find that the detection rates of Category 1 MgⅡabsorption lines(predominantly intervening absorbers)show no correlation with the blueshifted asymmetries of[OⅢ]emission lines,whereas the detection rates of Category 2 MgⅡabsorption lines(primarily outflow and intervening absorbers)increase with risingδ_(v).Finally,we discuss the results from two perspectives:quasar evolutionary stages and acceleration mechanisms driven by radiation pressure.
基金supported by the National Key R&D Program of China (grant No. 2022YFA1602902)the National Natural Science Foundation of China (grant Nos. 12433003, 11821303 and 11973030)the China Manned Space Program through its Space Application System.
文摘This is the second paper in a series that utilizes integral field spectroscopy from MaNGA,NUV imaging from Swift/UVOT,and NIR imaging from 2MASS to investigate dust attenuation properties on kpc scales in nearby galaxies.We apply the method developed in our previous work to the updated SwiM_v4.2 catalog,and measure the optical attenuation curve and the attenuation in three NUV bands for 2487 spaxels selected from 91 galaxies with S/N> 20 and AV> 0.25.We classify all spaxels into two subsets:star-forming(SF) regions and non-SF regions.We explore the correlations of optical opacity(A_(V)) and the optical and NUV slopes of the attenuation curves(A_(B)/A_(V) and A_(w2)/A_(w1)) with a broad range of stellar population and emission-line properties,including specific surface brightness of Hα emission(∑_(Hα)/∑_(*)),stellar age,stellar and gas-phase metallicity,and diagnostics of recent star formation history.Overall,when comparing SF and non-SF regions,we find that A_(V) and A_(B)/A_(V) exhibit similar correlations with all the stellar population and emission-line properties considered,while the NUV slopes in SF regions tend to be flatter than those in non-SF regions.The NUV slope A_(w2)/A_(w1) exhibits an anti-correlation with ∑_(Hα)/∑_(*),a trend that is primarily driven by the positive correlation between A_(w2)/A_(w1) and ∑_(*).The NUV slope flattens in SF regions that contain young stellar populations and have experienced recent star formation,but it shows no obvious dependence on stellar or gas-phase metallicity.The spatially resolved dust attenuation properties exhibit no clear correlations with the inclination of host galaxies or the galactocentric distance of the regions.This finding reinforces the conclusion from Paper I that dust attenuation is primarily regulated by local processes on kpc scales or smaller,rather than by global processes at galactic scales.
基金supported by the National Key Research and Development Program of China No.2024YFA1611902the National Natural Science Foundation of China(NSFC)under grants Nos.12273027 and 12588202+3 种基金the Innovation Team Funds of China West Normal University under grant No.KCXTD2022-6CAS Project for Young Scientists in Basic Research under grants Nos.YSBR-062 and YSBR-092the Strategic Priority Research Program of Chinese Academy of Sciences under grant No.XDB1160102the science research grant from the China Manned Space Project with No.CMS-CSST-2025-A11.
文摘Based on the updated M giant star catalog selected from Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR9,we identify substructures within the integrals-of-motion space through the Friends-of-Friends clustering algorithm.We obtain members belonging to several known substructures:the Sagittarius stream,Galactic Anticenter Substructure(GASS),Gaia-Enceladus-Sausage(GES),Splash,and the high-αdisk.Furthermore,we also identify two groups which cannot be clearly associated with previously known substructures.Our findings confirm the existence of metal-rich constituents within the GES,representing newly formed stars that originated from the metal-enriched gas delivered during the GES merger event and subsequently evolved.Additionally,this study further expands the sample of GASS,high-αdisk,and Splash stars.Analysis of these metal-rich M giant stars as members of the GES,Splash,and high-αdisk components supports an evolution scenario for the early Milky Way,as proposed by previous studies.In this scenario,stars initially formed in a high-α primordial disk were dynamically heated by the massive accretion event(GES).This process redistributed stellar orbits,creating the Splash population,while the undisturbed portion of the primordial disk persisted as the present-day high-αdisk component.
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 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 Key Research Development Program of China(grant Nos.2022YFA1602902 and 2022YFA1602903)。
文摘Superthin galaxies are observed to have stellar disks with extremely small minor-to-major axis ratios.In this work,we investigate the formation of superthin galaxies in the TNG100 simulation.We trace the merger history and investigate the evolution of galaxy properties of a selected sample of superthin galaxies and a control sample of galaxies that share the same joint probability distribution in the stellar-mass and color diagram.Through making comparisons between the two galaxy samples,we find that present-day superthin galaxies had similar morphologies as the control sample counterparts at higher redshifts,but have developed extended flat“superthin”morphologies since z~1.During this latter evolution stage,superthin galaxies undergo an overwhelmingly higher frequency of prograde mergers(with orbit-spin angleθ_(orb)≤40°).Accordingly the spins of their dark matter halos have grown significantly and become noticeably higher than those of their normal disk counterparts.This further results in the buildup of their stellar disks at larger distances much beyond the regimes of normal disk galaxies.We also discuss the formation scenario of those superthin galaxies that live in larger dark matter halos as satellite galaxies therein.
基金supported by the National Key R&D Program of China(2022YFA1602901)the National Natural Science Foundation of China(NSFC,grant No.12373001)supported by the Open Project Program of the Key Laboratory of FAST,NAOC,Chinese Academy of Sciences。
文摘We report a new high-sensitivity HⅠmapping observation of the NGC 5055 galaxy group over an area of 1°.5×0°.75 with the Five-hundred-meter Aperture Spherical radio Telescope(FAST).Our observation reveals that the warped HⅠdisk of NGC 5055 is more extended than what was previously observed by WSRT,out to239(61.7 kpc).The total HⅠmass of NGC 5055 is determined to be~1.1×10^(10)M_Θ.We identified three HⅠclouds with HⅠmasses of the order of~10^(7)M_Θat the southeastern edge of the HⅠdisk,as well as a candidate high-velocity cloud with an HⅠmass of(1.2±0.5)×10^(6)M_Θto the north of NGC 5055.The HⅠcontent of UGCA337 is robustly detected for the first time by the FAST observations.It has a narrow HⅠlinewidth of W_(50)=17.4±3.8 km s^(-1)with a total HⅠmass of(3.5±0.3)×10^(6)M_Θ.Comparing the gas content and g-r color of UGCA 337 with typical low-mass dwarf galaxies,UGCA 337 appears relatively gas-poor despite its blue color.This suggests that UGCA 337 may have undergone gas stripping in the past.We also analyzed the possible origin of the diffuse HⅠclouds located at the outskirts of NGC 5055,and speculate that they might be the remnant features of a merger event in the past.
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 No.2107YFA0402600。
文摘Compact groups have high galaxy densities and low velocity dispersions,and their group members have experienced numerous and frequent interactions during their lifetimes.They provide a unique environment to study the evolution of galaxies.We examined the galaxies types and H I contents in groups to make a study on the galaxy evolution in compact groups.We used the group crossing time as an age indicator for galaxy groups.Our sample is derived from the Hickson Compact Group catalog.We obtained group morphology data from the Hyper-Leda database and the IR classification based on Wide-Field Infrared Survey Explorer fluxes from Zucker et al.By cross-matching the latest released ALFALFA 100%H I source catalog with supplement by data found in literature,we obtained 40 galaxy groups with H I data available.We confirmed that the weak correlation between H I mass fraction and group crossing time found by Ai&Zhu in SDSS groups also exists in compact groups.We also found that the group spiral galaxy fraction is correlated with the group crossing time,but the actively star-forming galaxy fraction is not correlated with the group crossing time.These results seem to fit with the hypothesis that the sequential acquisition of neighbors from surrounding larger-scale structures has affected the morphology transition and star formation efficiency in compact groups.
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the financial support from the Council of Scientific&Industrial Research (CSIR),Government of India。
文摘We use the recently discovered simple photometric parameter Central Intensity Ratio(CIR)determined for a sample of 57 nearby(z<0.02)Seyfert galaxies to explore the central features of galaxies and their possible connection with galaxy evolution.The sample of galaxies shows strong anti-correlation between CIR and mass of their central supermassive black holes(SMBHs).The SMBH masses of ellipticals are systematically higher for a given CIR value than those for lenticulars and spirals in the sample.However,the correlation between CIR and central velocity dispersion is weak.CIR appears less influenced by the excess flux produced by the central engine in these galaxies,when compared to spectroscopic parameters like velocity dispersion and OⅣflux,and proves to be a fast and reliable tool for estimating central SMBH mass.
基金the 3D-HST Treasury Program (GO 12177 and 12328) with the NASA/ESA HSTsupported by the National Natural Science Foundation of China (Nos. 11673004, 11873032 and 11433005)by the Research Fund for the Doctoral Program of Higher Education of China (No. 20133207110006)he support from Yunnan young and middleaged academic and technical leaders reserve talent program (No. 201905C160039)
文摘Based on a large sample of massive(M* 1010 M⊙) compact galaxies at 1.0 < z < 3.0 in five 3 D-HST/CANDELS fields, we quantify the fractional abundance and comoving number density of massive compact galaxies as a function of redshift. The samples of compact quiescent galaxies(cQGs) and compact star-forming galaxies(cSFGs) are constructed by various selection criteria of compact galaxies in the literature, and the effect of compactness definition on abundance estimate has proven to be remarkable,particularly for the cQGs and cSFGs at high redshifts. Regardless of the compactness criteria adopted,their overall redshift evolutions of fractional abundance and number density are found to be rather similar.Large samples of the cQGs exhibit a sustained increase in number density from z ~ 3 to 2 and a plateau at 1 < z < 2. For massive cSFGs, a plateau in the number density at 2 < z < 3 can be found, as well as a continuous drop from z ~ 2 to 1. The evolutionary trends of the cQG and cSFG abundances support the scenario that the cSFGs at z≥ 2 may have been rapidly quenched into quiescent phase via violent dissipational processes, such as major merger and disk instabilities. The rarity of the cSFGs at lower redshifts(z < 1) can be interpreted by the decrease of gas reservoirs in dark matter halos and the consequent low efficiency of gas-rich dissipation.
基金supported by the National Key R&D Program of China(Nos.2018YFE0202900 and 2022YFA1602901)the NSFC grant(Nos.11988101,11873051 and 12125302)+6 种基金NSFC grant(No.12033008)CAS Project for Young Scientists in Basic Research Grant(No.YSBR-062)the K.C.Wong Education Foundationthe National Key Research and Development of China(No.2018YFA0404503)the support by the National Natural Science Foundation of China(Nos.12047569 and 12147217)the science research grants from the China Manned Space Project with Nos.CMSCSST-2021-A03 and CMS-CSST-2021-A07by the Natural Science Foundation of Jilin Province,China(No.20180101228JC)。
文摘The observational data of high redshift galaxies become increasingly abundant,especially since the operation of the James Webb Space Telescope,which allows us to verify and optimize the galaxy formation model at high redshifts.In this work,we investigate the merging history of massive galaxies at 3<z<6 using a well-developed semi-analytic galaxy formation catalog.We find that the major merger rate increases with redshift up to 3 and then flattens.The fraction of wet mergers,during which the sum of the cold gas mass is higher than the sum of the stellar mass in two merging galaxies,also increases from~34%at z=0 to 96%at z=3.Interestingly,almost all major mergers are wet at z>3.This can be attributed to the high fraction(>50%)of cold gas at z>3.In addition,we study some special systems of massive merging galaxies at 3<z<6,including the massive gas-rich major merging systems and extreme dense proto-clusters,and investigate the supermassive black hole-dark matter halo mass relation and dual active galactic nuclei.We find that the galaxy formation model reproduces the incidence of those observed massive galaxies,but fails to reproduce the relation between the supermassive black hole mass and the dark matter halo mass at z~6.The latter requires more careful estimates of the supermassive black hole masses observationally.Otherwise,it could suggest modifications of the modeling of the supermassive black hole growth at high redshifts.
基金financial support from the SERB,DST,Government of India through the project CRG/2019/001110IUCAA,Pune for providing support through an associateship program+1 种基金IISER Tirupati for support through a postdoctoral fellowshipFunding for the SDSS and SDSS-Ⅱhas been provided by the Alfred P.Sloan Foundation,the U.S.Department of Energy,the National Aeronautics and Space Administration,the Japanese Monbukagakusho,the Max Planck Society,and the Higher Education Funding Council for England。
文摘Major interactions are known to trigger star formation in galaxies and alter their color.We study the major interactions in filaments and sheets using SDSS data to understand the influence of large-scale environments on galaxy interactions.We identify the galaxies in filaments and sheets using the local dimension and also find the major pairs residing in these environments.The star formation rate(SFR) and color of the interacting galaxies as a function of pair separation are separately analyzed in filaments and sheets.The analysis is repeated for three volume limited samples covering different magnitude ranges.The major pairs residing in the filaments show a significantly higher SFR and bluer color than those residing in the sheets up to the projected pair separation of~50 kpc.We observe a complete reversal of this behavior for both the SFR and color of the galaxy pairs having a projected separation larger than 50 kpc.Some earlier studies report that the galaxy pairs align with the filament axis.Such alignment inside filaments indicates anisotropic accretion that may cause these differences.We do not observe these trends in the brighter galaxy samples.The pairs in filaments and sheets from the brighter galaxy samples trace relatively denser regions in these environments.The absence of these trends in the brighter samples may be explained by the dominant effect of the local density over the effects of the large-scale environment.
基金the Chinese Acadeinv of Sciences,the Chinese National Naturnal Science Foundation and the Ministry of sciences and technology of ChinaThe project is also supported in part by the National Science Foundation(grant IXT 93-01805)by Arizona State University,the University of Arizona and Western Connecticut State University
文摘Based on the method proposed by Kong et al. and on the multi-color spectrophotometry by Ma et al., we estimate the metallicities of 16 old star clusters in the nearby spiral galaxy M33, ten of which are halo globular clusters. These old clusters are all metal poor, the range of metallicity ([Fe/H]) is from-0.14 to-2.12. In general, our results are consistent with those derived by other methods, such as integrated spectra and photometry, and our study confirms the reliability of the method of Kong et al.
