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
As an alternative gravitational theory to general relativity(GR),conformal gravity(CG)has recently been successfully veri/ed by observations of type Ia supernovae(SN Ia)and the rotation curves of spiral galaxies.The o...As an alternative gravitational theory to general relativity(GR),conformal gravity(CG)has recently been successfully veri/ed by observations of type Ia supernovae(SN Ia)and the rotation curves of spiral galaxies.The observations of galaxies only pertain to the non-relativistic form of gravity.In this context,within the framework of the Newtonian theory of gravity(the non-relativistic form of GR),dark matter(DM)is postulated to account for the observations.On the other hand,the non-relativistic form of CG predicts an additional potential:besides the Newtonian potential,there is a so-called linear potential term,characterized by the parameterγ*,as an alternative to DM in Newtonian gravity.To test CG in its non-relativistic form,much work has been done by/tting the predictions to the observations of circular velocity(rotation curves)for spiral galaxies.In this paper,we test CG with the observations from elliptical galaxies.Instead of the circular velocities for spiral galaxies,we use the velocity dispersion for elliptical galaxies.By replacing the Newtonian potential with that predicted by the nonrelativistic form of CG in the Hamiltonian,we directly extend the Jeans equation derived in Newtonian theory to that for CG.By comparing the results derived from the ellipticals with those from spirals,we/nd that the extra potential predicted by CG is not suf/cient to account for the observations of ellipticals.Furthermore,we discover a strong correlation betweenγ*and the stellar mass M*in dwarf spheroidal galaxies.This/nding implies that the variation inγ*violates a fundamental prediction of CG,which posits thatγ*should be a universal constant.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 results from our Giant Metrewave Radio Telescope(GMRT)HⅠ,Himalayan Chandra Telescope(HCT)Hα,1 m Sampurnanand Telescope(ST)and 1.3 m Devasthal Fast Optical Telescope(DFOT)deep optical observations of the N...We present results from our Giant Metrewave Radio Telescope(GMRT)HⅠ,Himalayan Chandra Telescope(HCT)Hα,1 m Sampurnanand Telescope(ST)and 1.3 m Devasthal Fast Optical Telescope(DFOT)deep optical observations of the NGC 7805/6(Arp 112)system to test KUG 2359+311’s tidal dwarf galaxy(TDG)candidacy and explore the properties of the interacting system.Our GMRT HⅠmap shows no HⅠdetection associated with KUG 2359+311,nor any HⅠtail or bridge-like structure connecting KUG 2359+311 to the NGC 7805/6 system.Our HCT Hαimage,on the other hand,displays strong detections in KUG 2359+311,with net SFR0.035±0.009 M_(⊙)yr^(-1).The Hαdata constrain the redshift of KUG 2359+311 to 0.00≤z≤0.043,compared to the redshift of NGC 7806 of0.015.TDGs detected to date have all been HⅠrich,and displayed HⅠ,ionised gas and stellar tidal debris trails(bridges or tails)linking them to their parent systems.However,neither our HⅠdata nor our optical imaging,while three magnitudes deeper than SDSS,reveals a tidal trail connecting KUG 2359+311 to NGC 7805/6.Lack of HⅠ,presence of an old stellar population,ongoing star formation and reasonably high SFR compared to normal dwarf galaxies suggest that KUG 2359+311 may not be an Arp 112 TDG.It is most likely a case of a regular gas-rich dwarf galaxy undergoing a morphological transformation after having lost its entire gas content to an interaction with the Arp 112 system.Redshift and metallicity from future spectroscopic observations of KUG 2359+311 would help clarify the nature of this enigmatic structure.展开更多
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supported by the National Natural Science Foundation of China(NSFC,grant No.11988101)the K.C.Wong Education Foundation.
文摘As an alternative gravitational theory to general relativity(GR),conformal gravity(CG)has recently been successfully veri/ed by observations of type Ia supernovae(SN Ia)and the rotation curves of spiral galaxies.The observations of galaxies only pertain to the non-relativistic form of gravity.In this context,within the framework of the Newtonian theory of gravity(the non-relativistic form of GR),dark matter(DM)is postulated to account for the observations.On the other hand,the non-relativistic form of CG predicts an additional potential:besides the Newtonian potential,there is a so-called linear potential term,characterized by the parameterγ*,as an alternative to DM in Newtonian gravity.To test CG in its non-relativistic form,much work has been done by/tting the predictions to the observations of circular velocity(rotation curves)for spiral galaxies.In this paper,we test CG with the observations from elliptical galaxies.Instead of the circular velocities for spiral galaxies,we use the velocity dispersion for elliptical galaxies.By replacing the Newtonian potential with that predicted by the nonrelativistic form of CG in the Hamiltonian,we directly extend the Jeans equation derived in Newtonian theory to that for CG.By comparing the results derived from the ellipticals with those from spirals,we/nd that the extra potential predicted by CG is not suf/cient to account for the observations of ellipticals.Furthermore,we discover a strong correlation betweenγ*and the stellar mass M*in dwarf spheroidal galaxies.This/nding implies that the variation inγ*violates a fundamental prediction of CG,which posits thatγ*should be a universal constant.
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support by Fundacao paraa Ciencia e a Tecnologia(FCT)through national funds(UID/FIS/04434/2013)FCT/MCTES through national funds(PIDDAC)by this grant UID/FIS/04434/2019+3 种基金by FEDER through COMPETE2020(POCI-01-0145FED ER-007672)support from DL 57/2016/CP1364/CT0009the support of NRF(Grant Nos.105925,109577,120385,and 120378)the National Natural Science Foundation of China(Grant No.11828301)。
文摘We present results from our Giant Metrewave Radio Telescope(GMRT)HⅠ,Himalayan Chandra Telescope(HCT)Hα,1 m Sampurnanand Telescope(ST)and 1.3 m Devasthal Fast Optical Telescope(DFOT)deep optical observations of the NGC 7805/6(Arp 112)system to test KUG 2359+311’s tidal dwarf galaxy(TDG)candidacy and explore the properties of the interacting system.Our GMRT HⅠmap shows no HⅠdetection associated with KUG 2359+311,nor any HⅠtail or bridge-like structure connecting KUG 2359+311 to the NGC 7805/6 system.Our HCT Hαimage,on the other hand,displays strong detections in KUG 2359+311,with net SFR0.035±0.009 M_(⊙)yr^(-1).The Hαdata constrain the redshift of KUG 2359+311 to 0.00≤z≤0.043,compared to the redshift of NGC 7806 of0.015.TDGs detected to date have all been HⅠrich,and displayed HⅠ,ionised gas and stellar tidal debris trails(bridges or tails)linking them to their parent systems.However,neither our HⅠdata nor our optical imaging,while three magnitudes deeper than SDSS,reveals a tidal trail connecting KUG 2359+311 to NGC 7805/6.Lack of HⅠ,presence of an old stellar population,ongoing star formation and reasonably high SFR compared to normal dwarf galaxies suggest that KUG 2359+311 may not be an Arp 112 TDG.It is most likely a case of a regular gas-rich dwarf galaxy undergoing a morphological transformation after having lost its entire gas content to an interaction with the Arp 112 system.Redshift and metallicity from future spectroscopic observations of KUG 2359+311 would help clarify the nature of this enigmatic structure.
