We summarize several measurements of the dark matter temperature-to-mass ratio, or equivalently, of the comoving root-mean-square thermal velocity of warm dark matter particles vhrms(1). The most reliable determinatio...We summarize several measurements of the dark matter temperature-to-mass ratio, or equivalently, of the comoving root-mean-square thermal velocity of warm dark matter particles vhrms(1). The most reliable determination of this parameter comes from well measured rotation curves of dwarf galaxies by the LITTLE THINGS collaboration: vhrms(1)=406±69 m/s. Complementary and consistent measurements are obtained from rotation curves of spiral galaxies measured by the SPARC collaboration, density runs of giant elliptical galaxies, galaxy ultra-violet luminosity distributions, galaxy stellar mass distributions, first galaxies, and reionization. Having measured vhrms(1), we then embark on a journey to the past that leads to a consistent set of measured dark matter properties, including mass, temperature and spin.展开更多
The recently discovered satellite dwarf galaxy Ursa Major III provides a promising opportunity to explore the signatures resulting from dark matter(DM)annihilation owing to its proximity and large J-factor.Given the a...The recently discovered satellite dwarf galaxy Ursa Major III provides a promising opportunity to explore the signatures resulting from dark matter(DM)annihilation owing to its proximity and large J-factor.Given the absence of an excess ofγ-ray signatures originating from Ursa Major III,observations ofγ-rays,such as those from Fermi-LAT,can be utilized to set constraints on the DM annihilation cross-section.In this study,we determined the DM density profile and considered the relationship between DM density and velocity dispersion at different locations within Ursa Major III through Jeans analysis.We calculated the J-factor of Ursa Major III for s-wave annihilation along with the effective J-factors for p-wave and Sommerfeld enhanced annihilation scenarios.Employing these derived J-factors,we set stringent constraints on DM annihilation cross-sections in three scenarios.Given the substantial impact of member star identification on the J-factor of Ursa Major III,we further calculated J-factors under the exclusion of the largest velocity outlier.Our analysis reveals a notable reduction in the median value and an increase in the deviation of J-factors,thereby leading to considerably weaker constraints.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
Recently, many new dwarf spheroidal satellites（dSphs） have been discovered by the Dark Energy Survey（DES）. These dSphs are ideal candidates for probing for gamma-ray emissions from dark matter（DM） annihilation.H...Recently, many new dwarf spheroidal satellites（dSphs） have been discovered by the Dark Energy Survey（DES）. These dSphs are ideal candidates for probing for gamma-ray emissions from dark matter（DM） annihilation.However, no significant signature has been found by the Fermi-LAT dSph observations. In this work, we reanalyze the Fermi-LAT Pass 8 data from the direction of Reticulum II, where a slight excess has been reported by some previous studies. We treat Reticulum II（DES J0335.6-5403） as a spatially extended source, and find that no significant gamma-ray signature is observed. Based on this result, we set upper-limits on the DM annihilation cross section.展开更多
The motion of baryonic components of the Milky Way is governed by both luminous and dark matter content of the Galaxy.Thus,the dynamics of Milky Way globular clusters(GCs)can be used as tracers to infer the mass model...The motion of baryonic components of the Milky Way is governed by both luminous and dark matter content of the Galaxy.Thus,the dynamics of Milky Way globular clusters(GCs)can be used as tracers to infer the mass model of the Galaxy up to a large radius.In this work,we apply the directly observable line-of-sight velocities to test if the dynamics of the GC population are consistent with an assumed axisymmetric gravitational potential of the Milky Way.For this,we numerically compute the phase space distribution of the GC population where the orbits are either oriented randomly or co-/counter-rotating with respect to the stellar disk.Then we compare the observed position and line-of-sight velocity distribution of^150 GCs with those of the models.We found that,for the adopted mass model,the co-rotating scenario is the favored model based on various statistical tests.We do the analysis with and without the GCs associated with the progenitors of early merger events.This analysis can be extended in the near future to include precise and copious data to better constrain the Galactic potential up to a large radius.展开更多
As a next-generation complex extensive air shower array with a large field of view,the large high altitude air shower observatory(LHAASO)is very sensitive to the very-high-energy gamma rays from^300 GeV to 1 PeV and m...As a next-generation complex extensive air shower array with a large field of view,the large high altitude air shower observatory(LHAASO)is very sensitive to the very-high-energy gamma rays from^300 GeV to 1 PeV and may thus serve as an important probe for the heavy dark matter(DM)particles.In this study,we make a forecast for the LHAASO sensitivities to the gamma-ray signatures resulting from DM decay in dwarf spheroidal satellite galaxies(dSphs)within the LHAASO field of view.Both individual and combined limits for 19 dSphs incorporating the uncertainties of the DM density profile are explored.Owing to the large effective area and strong capability of the photon-proton discrimination,we find that LHASSSO is sensitive to the signatures from decaying DM particles above O(1)TeV.The LHAASO sensitivity to the DM decay lifetime reaches O(1026)∼O(1028)s for several decay channels at the DM mass scale from 1 TeV to 100 TeV.展开更多
In recent years it has become clear that the Milky Way is an important test- ing ground for theories of galaxy formation. Much of this growth has been driven by large surveys, both photometric and spectroscopic, which...In recent years it has become clear that the Milky Way is an important test- ing ground for theories of galaxy formation. Much of this growth has been driven by large surveys, both photometric and spectroscopic, which are producing vast and rich catalogs of data. Through the analysis of these data sets we can gain new and detailed insights into the physical processes which shaped the Milky Way＇s evolution. This review will discuss a number of these developments, first focusing on the disk of the Milky Way, and then looking at its satellite population. The importance of surveys has not gone unnoticed by the Chinese astronomy community and in the final section we discuss a number of Chinese projects that are set to play a key role in the development of this field.展开更多
Warm dark matter has, by definition, a velocity dispersion. Let v<sub>hms</sub>(a)=v<sub>hms</sub><sub></sub>(1)/a be the root-mean-square velocity of non-relativistic warm dark mat...Warm dark matter has, by definition, a velocity dispersion. Let v<sub>hms</sub>(a)=v<sub>hms</sub><sub></sub>(1)/a be the root-mean-square velocity of non-relativistic warm dark matter particles in the early universe at expansion parameter a. v<sub>hms</sub><sub></sub>(1) is an adiabatic invariant. We obtain v<sub>hms</sub><sub></sub>(1) in the core of 11 dwarf galaxies dominated by dark matter, from their observed rotation curves, up to a rotation and relaxation correction. We obtain a mean 0.490 km/s and standard deviation 0.160 km/s, with a distribution peaked at the lower end. We apply a mild, data driven, rotation and relaxation correction that obtains the adiabatic invariant in the core of the galaxies: v<sub>hms</sub></sub>(1)=0.406 ±0.069 km/s. These two small relative standard deviations justify the prediction that the adiabatic invariant v<sub>hms</sub><sub></sub>(1) in the core of the galaxies is of cosmological origin if dark matter is warm. This result is in agreement with measurements of v<sub>hms</sub></sub>(1) based on spiral galaxy rotation curves, galaxy ultra-violet luminosity distributions, galaxy stellar mass distributions, the formation of first galaxies, reionization, and the velocity dispersion cut-off mass.展开更多
文摘We summarize several measurements of the dark matter temperature-to-mass ratio, or equivalently, of the comoving root-mean-square thermal velocity of warm dark matter particles vhrms(1). The most reliable determination of this parameter comes from well measured rotation curves of dwarf galaxies by the LITTLE THINGS collaboration: vhrms(1)=406±69 m/s. Complementary and consistent measurements are obtained from rotation curves of spiral galaxies measured by the SPARC collaboration, density runs of giant elliptical galaxies, galaxy ultra-violet luminosity distributions, galaxy stellar mass distributions, first galaxies, and reionization. Having measured vhrms(1), we then embark on a journey to the past that leads to a consistent set of measured dark matter properties, including mass, temperature and spin.
基金Supported by the National Natural Science Foundation of China (11947005,12175248,12205388,12227804)the Science&Technology Development Fund of Tianjin Education Commission for Higher Education (2020KJ003)the PhD Research Startup Foundation of Tianjin Normal University (52XB1912)。
文摘The recently discovered satellite dwarf galaxy Ursa Major III provides a promising opportunity to explore the signatures resulting from dark matter(DM)annihilation owing to its proximity and large J-factor.Given the absence of an excess ofγ-ray signatures originating from Ursa Major III,observations ofγ-rays,such as those from Fermi-LAT,can be utilized to set constraints on the DM annihilation cross-section.In this study,we determined the DM density profile and considered the relationship between DM density and velocity dispersion at different locations within Ursa Major III through Jeans analysis.We calculated the J-factor of Ursa Major III for s-wave annihilation along with the effective J-factors for p-wave and Sommerfeld enhanced annihilation scenarios.Employing these derived J-factors,we set stringent constraints on DM annihilation cross-sections in three scenarios.Given the substantial impact of member star identification on the J-factor of Ursa Major III,we further calculated J-factors under the exclusion of the largest velocity outlier.Our analysis reveals a notable reduction in the median value and an increase in the deviation of J-factors,thereby leading to considerably weaker constraints.
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 National Natural Science Foundation of China(11121092,11033005,11375202,11475191,11475189)the CAS pilot B program(XDB23020000)the National Key Program for Research and Development(2016YFA0400200)
文摘Recently, many new dwarf spheroidal satellites（dSphs） have been discovered by the Dark Energy Survey（DES）. These dSphs are ideal candidates for probing for gamma-ray emissions from dark matter（DM） annihilation.However, no significant signature has been found by the Fermi-LAT dSph observations. In this work, we reanalyze the Fermi-LAT Pass 8 data from the direction of Reticulum II, where a slight excess has been reported by some previous studies. We treat Reticulum II（DES J0335.6-5403） as a spatially extended source, and find that no significant gamma-ray signature is observed. Based on this result, we set upper-limits on the DM annihilation cross section.
基金the Infosys Foundation through the Infosys Young Investigator grant。
文摘The motion of baryonic components of the Milky Way is governed by both luminous and dark matter content of the Galaxy.Thus,the dynamics of Milky Way globular clusters(GCs)can be used as tracers to infer the mass model of the Galaxy up to a large radius.In this work,we apply the directly observable line-of-sight velocities to test if the dynamics of the GC population are consistent with an assumed axisymmetric gravitational potential of the Milky Way.For this,we numerically compute the phase space distribution of the GC population where the orbits are either oriented randomly or co-/counter-rotating with respect to the stellar disk.Then we compare the observed position and line-of-sight velocity distribution of^150 GCs with those of the models.We found that,for the adopted mass model,the co-rotating scenario is the favored model based on various statistical tests.We do the analysis with and without the GCs associated with the progenitors of early merger events.This analysis can be extended in the near future to include precise and copious data to better constrain the Galactic potential up to a large radius.
基金Supported by the National Key R&D Program of China(2016YFA0400200)the National Natural Science Foundation of China(U1738209,11851303,11835009,11975072)the National Program for Support of Top-Notch Young Professionals。
文摘As a next-generation complex extensive air shower array with a large field of view,the large high altitude air shower observatory(LHAASO)is very sensitive to the very-high-energy gamma rays from^300 GeV to 1 PeV and may thus serve as an important probe for the heavy dark matter(DM)particles.In this study,we make a forecast for the LHAASO sensitivities to the gamma-ray signatures resulting from DM decay in dwarf spheroidal satellite galaxies(dSphs)within the LHAASO field of view.Both individual and combined limits for 19 dSphs incorporating the uncertainties of the DM density profile are explored.Owing to the large effective area and strong capability of the photon-proton discrimination,we find that LHASSSO is sensitive to the signatures from decaying DM particles above O(1)TeV.The LHAASO sensitivity to the DM decay lifetime reaches O(1026)∼O(1028)s for several decay channels at the DM mass scale from 1 TeV to 100 TeV.
基金Supported by the National Natural Science Foundation of Chinathe Peking University One Hundred Talent Fund (985)the National Natural Science Foundation of China (Grant Nos. 11173002 and11010022)
文摘In recent years it has become clear that the Milky Way is an important test- ing ground for theories of galaxy formation. Much of this growth has been driven by large surveys, both photometric and spectroscopic, which are producing vast and rich catalogs of data. Through the analysis of these data sets we can gain new and detailed insights into the physical processes which shaped the Milky Way＇s evolution. This review will discuss a number of these developments, first focusing on the disk of the Milky Way, and then looking at its satellite population. The importance of surveys has not gone unnoticed by the Chinese astronomy community and in the final section we discuss a number of Chinese projects that are set to play a key role in the development of this field.
文摘Warm dark matter has, by definition, a velocity dispersion. Let v<sub>hms</sub>(a)=v<sub>hms</sub><sub></sub>(1)/a be the root-mean-square velocity of non-relativistic warm dark matter particles in the early universe at expansion parameter a. v<sub>hms</sub><sub></sub>(1) is an adiabatic invariant. We obtain v<sub>hms</sub><sub></sub>(1) in the core of 11 dwarf galaxies dominated by dark matter, from their observed rotation curves, up to a rotation and relaxation correction. We obtain a mean 0.490 km/s and standard deviation 0.160 km/s, with a distribution peaked at the lower end. We apply a mild, data driven, rotation and relaxation correction that obtains the adiabatic invariant in the core of the galaxies: v<sub>hms</sub></sub>(1)=0.406 ±0.069 km/s. These two small relative standard deviations justify the prediction that the adiabatic invariant v<sub>hms</sub><sub></sub>(1) in the core of the galaxies is of cosmological origin if dark matter is warm. This result is in agreement with measurements of v<sub>hms</sub></sub>(1) based on spiral galaxy rotation curves, galaxy ultra-violet luminosity distributions, galaxy stellar mass distributions, the formation of first galaxies, reionization, and the velocity dispersion cut-off mass.
