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
Recent JWST observations have revealed that dwarf galaxies start to cease star formation at redshifts z>1,yet the quenching process remains unclear.In this study,we selected a large sample of 3405 dwarf galaxies wi...Recent JWST observations have revealed that dwarf galaxies start to cease star formation at redshifts z>1,yet the quenching process remains unclear.In this study,we selected a large sample of 3405 dwarf galaxies with stellar masses below 109.5Me and redshifts ranging from 1.0 to 1.5 across all five CANDELS fields.By utilizing multi-wavelength imaging data from both JWST and HST,we examined the growth patterns and modes of star formation quenching in dwarf galaxies during the cosmic noon era.Based on their specific star formation rates (sS FR),we categorized the sample into three subgroups:star-forming dwarf galaxies below and above the star formation main sequence (SFMS),and quiescent dwarf galaxies.To analyze the UVJ color profiles of these three subgroups of dwarf galaxies,we applied the image stacking technique.This method improves the signal-to-noise ratio and extends the color profiles to the outer regions of the galaxies.Our results show that these galaxies generally exhibit nearly flat stacked color profiles,suggesting that,on average,their growth and star formation quenching patterns are self-similar,differing from those previously observed in dwarf galaxies at lower redshifts.We further discuss the potential roles of internal and external physical processes in the star formation quenching of dwarf galaxies during the cosmic noon period.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 Wide Field Survey Telescope(WFST)is a dedicated time-domain multi-band(u,g,r,i,and z)photometric survey facility under construction.In this paper,we present a preliminary study that assesses the quality of photome...The Wide Field Survey Telescope(WFST)is a dedicated time-domain multi-band(u,g,r,i,and z)photometric survey facility under construction.In this paper,we present a preliminary study that assesses the quality of photometric redshifts based on WFST by utilizing mock observations derived with the galaxy catalog in the COSMOS/UltraVISTA field.We apply the template fitting technique to estimate photometric redshifts by using the ZEBRA photometric-redshift code and adopting a modified set of adaptive templates.We evaluate the bias(median relative offset between the output photometric redshifts and input redshifts),normalized median absolute deviation(σ_(NMAD))and outlier fraction(f_(outlier))of photometric redshifts in two typical WFST observational cases,the single 30 s exposure observations(hereafter shallow mode)and co-added 50 minutes exposure observations(hereafter deep mode).We find bias≲0.006,σ_(NMAD)≲0.03,and f_(outlier)≲5%in the shallow mode and bias≈0.005,σ_(NMAD)≈0.06,and f_(outlier)≈17%–27%in the deep mode,respectively,under various lunar phases.Combining the WFST mock observational data with that from the upcoming CSST and Euclid surveys,we demonstrate that the zphot results can be significantly improved,with f_(outlier)≈1%andσ_(NMAD)≈0.02.展开更多
Recent observations with the James Webb Space Telescope(JWST)reveal that the merger fraction among Lyαemitters(LAEs)at redshifts z>3 is significantly higher than previously estimated.In this study,we focus on thre...Recent observations with the James Webb Space Telescope(JWST)reveal that the merger fraction among Lyαemitters(LAEs)at redshifts z>3 is significantly higher than previously estimated.In this study,we focus on three high signal-to-noise merging LAE systems at 3<z<4,selected from the Very Large Telescope/Multi Unit Spectroscopic Explorer-Deep survey in the GOODS-S field.We combine new JWST/NIRCam broadband and medium-band imaging with archival Hubble Space Telescope/ACS data to perform spatially resolved spectral energy distribution fitting using the BAGPIPES software package.Our analysis reveals that two of the systems are minor mergers,while the third is a major merger.The close agreement between spatially resolved and integrated stellar mass estimates indicates that recent star formation does not significantly outshine the light from older stellar populations in these systems.Moreover,both the individual components and the systems as a whole lie on the star-forming main sequence,further supporting the conclusion that these mergers have not yet triggered substantial starburst activity.Furthermore,we detect prominent color gradients and disturbed dust distributions in these merging systems,indicating that the mergers have already induced significant internal structural perturbations.These morphological and dust-related changes may facilitate the escape of Lyαphotons—potentially through mechanisms such as gas redistribution or a reduced covering fraction of neutral hydrogen—thereby playing a key role in shaping the observed properties of LAEs.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 National Natural Science Foundation of China (NSFC,grant Nos.12273052,11733006,12090040,12090041 and 12073051)the science research grants from the China Manned Space Project (No.CMS-CSST-2021-A04)+6 种基金the support from the Ministry of Science and Technology of China (No.2020SKA0110100)the science research grants from the China Manned Space Project (No.CMS-CSST-2021-A01)the CAS Project for Young Scientists in Basic Research (No.YSBR-062)supported by the National Key R&D Program(2023YFE0101200)the China Manned Space Project (No.CMS-CSST-2025-A07)the NSFC (grant No.12393813)the Yunnan Revitalization Talent Support Program (YunLing Scholar Project)。
文摘Recent JWST observations have revealed that dwarf galaxies start to cease star formation at redshifts z>1,yet the quenching process remains unclear.In this study,we selected a large sample of 3405 dwarf galaxies with stellar masses below 109.5Me and redshifts ranging from 1.0 to 1.5 across all five CANDELS fields.By utilizing multi-wavelength imaging data from both JWST and HST,we examined the growth patterns and modes of star formation quenching in dwarf galaxies during the cosmic noon era.Based on their specific star formation rates (sS FR),we categorized the sample into three subgroups:star-forming dwarf galaxies below and above the star formation main sequence (SFMS),and quiescent dwarf galaxies.To analyze the UVJ color profiles of these three subgroups of dwarf galaxies,we applied the image stacking technique.This method improves the signal-to-noise ratio and extends the color profiles to the outer regions of the galaxies.Our results show that these galaxies generally exhibit nearly flat stacked color profiles,suggesting that,on average,their growth and star formation quenching patterns are self-similar,differing from those previously observed in dwarf galaxies at lower redshifts.We further discuss the potential roles of internal and external physical processes in the star formation quenching of dwarf galaxies during the cosmic noon period.
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(2022YFF0503401)the National Natural Science Foundation of China(12203047,12025303,11890693,12003031)+1 种基金the science research grants from the China Manned Space Project with NO.CMSCSST-2021-A06the Fundamental Research Funds for the Central Universities(WK3440000006,WK2030000057)。
文摘The Wide Field Survey Telescope(WFST)is a dedicated time-domain multi-band(u,g,r,i,and z)photometric survey facility under construction.In this paper,we present a preliminary study that assesses the quality of photometric redshifts based on WFST by utilizing mock observations derived with the galaxy catalog in the COSMOS/UltraVISTA field.We apply the template fitting technique to estimate photometric redshifts by using the ZEBRA photometric-redshift code and adopting a modified set of adaptive templates.We evaluate the bias(median relative offset between the output photometric redshifts and input redshifts),normalized median absolute deviation(σ_(NMAD))and outlier fraction(f_(outlier))of photometric redshifts in two typical WFST observational cases,the single 30 s exposure observations(hereafter shallow mode)and co-added 50 minutes exposure observations(hereafter deep mode).We find bias≲0.006,σ_(NMAD)≲0.03,and f_(outlier)≲5%in the shallow mode and bias≈0.005,σ_(NMAD)≈0.06,and f_(outlier)≈17%–27%in the deep mode,respectively,under various lunar phases.Combining the WFST mock observational data with that from the upcoming CSST and Euclid surveys,we demonstrate that the zphot results can be significantly improved,with f_(outlier)≈1%andσ_(NMAD)≈0.02.
文摘Recent observations with the James Webb Space Telescope(JWST)reveal that the merger fraction among Lyαemitters(LAEs)at redshifts z>3 is significantly higher than previously estimated.In this study,we focus on three high signal-to-noise merging LAE systems at 3<z<4,selected from the Very Large Telescope/Multi Unit Spectroscopic Explorer-Deep survey in the GOODS-S field.We combine new JWST/NIRCam broadband and medium-band imaging with archival Hubble Space Telescope/ACS data to perform spatially resolved spectral energy distribution fitting using the BAGPIPES software package.Our analysis reveals that two of the systems are minor mergers,while the third is a major merger.The close agreement between spatially resolved and integrated stellar mass estimates indicates that recent star formation does not significantly outshine the light from older stellar populations in these systems.Moreover,both the individual components and the systems as a whole lie on the star-forming main sequence,further supporting the conclusion that these mergers have not yet triggered substantial starburst activity.Furthermore,we detect prominent color gradients and disturbed dust distributions in these merging systems,indicating that the mergers have already induced significant internal structural perturbations.These morphological and dust-related changes may facilitate the escape of Lyαphotons—potentially through mechanisms such as gas redistribution or a reduced covering fraction of neutral hydrogen—thereby playing a key role in shaping the observed properties of LAEs.
