We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9(z = 0.005)(hereafter J2306) and investigate whether it could be a Tidal Dwa...We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9(z = 0.005)(hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy(TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g-r color of 0.23 mag, irregular optical morphology and high-metallicity(12 +log(O/H) = 8.68 ± 0.14), making it an interesting galaxy to study in more detail. We find J2306 to be an H I rich galaxy with a large extended, unperturbed rotating H I disk. Using our H I data we estimated its dynamical mass and found the galaxy to be dark matter(DM) dominated within its H I radius. The quantity of DM, inferred from its dynamical mass, appears to rule out J2306 as an evolved TDG. A wide area environment search reveals J2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the H I morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity.Further detailed optical spectroscopic observations of J2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment.展开更多
We aim to understand the properties at the locations of supernova(SN) explosions in their host galaxies and compare with the global properties of these host galaxies. We use the integral field spectrograph(IFS) of Map...We aim to understand the properties at the locations of supernova(SN) explosions in their host galaxies and compare with the global properties of these host galaxies. We use the integral field spectrograph(IFS) of Mapping Nearby Galaxies at Apache Point Observatory(MaNGA) to generate 2 D maps of the parameter properties for 11 SN host galaxies. The sample galaxies are analyzed one by one in detail in terms of their properties of velocity field, star formation rate, oxygen abundance, stellar mass, etc.This sample of SN host galaxies has redshifts around z^0.03, which is higher than those of previous related works. The higher redshift distribution allows us to obtain the properties of more distant SN host galaxies. Metallicity(gas-phase oxygen abundance) estimated from integrated spectra can represent the local metallicity at SN explosion sites with small bias. All the host galaxies in our sample are metal-rich galaxies(12+log(O/H)> 8.5) except for NGC 6387, which means SNe may be more inclined to explode in metallicity-rich galaxies. There is a positive relation between global gas-phase oxygen abundance and the stellar mass of host galaxies. We also try to compare the differences of the host galaxies between SNe Ia and SNe II. In our sample, both SNe Ia and SNe II can explode in normal galaxies, but SNe II can also explode in an interacting or a merging system, in which star formation is occurring in the galaxy.展开更多
We extend Schwarzschild’s dynamical modelling method to model absorption line strength data as well as the more usual luminosity and kinematic data.Our approach draws on earlier published work by the first author wit...We extend Schwarzschild’s dynamical modelling method to model absorption line strength data as well as the more usual luminosity and kinematic data.Our approach draws on earlier published work by the first author with the Syer & Tremaine made-to-measure(M2M) dynamical modelling method and uses similar ideas to create a chemo-Schwarzschild method.We apply our extended Schwarzschild method to the same four early type galaxies(NGC 1248, NGC 3838, NGC 4452,NGC 4551) as the chemo-M2M work, and are able to recover successfully the 2D absorption line strength for the three lines we model(Hβ, Fe5015, Mg b).We believe that this is the first time Schwarzschild’s method has been used in this way.The techniques developed can be applied to modelling other aspects of galaxies, for example age and metallicity data coming from stellar population modelling, and are not specific to absorption line strength data.展开更多
The overabundance of the red and massive candidate galaxies observed by the James Webb Space Telescope(JWST)implies efficient structure formation or large star formation efficiency at high redshift z~10.In the scenari...The overabundance of the red and massive candidate galaxies observed by the James Webb Space Telescope(JWST)implies efficient structure formation or large star formation efficiency at high redshift z~10.In the scenario of a low or moderate star formation efficiency,because massive neutrinos tend to suppress the growth of structure of the universe,the JWST observation tightens the upper bound of the neutrino masses.Assuming A cold dark matter cosmology and a star formation efficiency∈[0.05,0.3](flat prior),we perform joint analyses of Planck+JWST and Planck+BAO+JWST,and obtain improved constraints∑m_(ν)<0.196 eV and ∑m_(ν)+<0.111 eV at 95% confidence level,respectively.Based on the above assumptions,the inverted mass ordering,which implies ∑m_(ν)≥0.1 eV,is excluded by Planck+BAO+JWST at 92.7% confidence level.展开更多
We present an analysis of the metallicity and star formation activities of H II regions in the interacting system Arp 86, based on the first scientific observations using mulri-object spectroscopy with the 2.16 m tele...We present an analysis of the metallicity and star formation activities of H II regions in the interacting system Arp 86, based on the first scientific observations using mulri-object spectroscopy with the 2.16 m telescope at the Xinglong Observing Station. We find that the oxygen abundance gradient in Arp 86 is flatter than that in normal disk galaxies, which confirms that gas inflows caused by tidal forces during encounters can flatten the metallicity distributions in galaxies. The companion galaxy NGC 7752 is currently experiencing a galaxy-wide starburst with a higher star for- marion rate surface density than the main galaxy NGC 7753, which can be explained in that the companion galaxy is more susceptible to the effects of interaction than the primary. We also find that the galaxy 2MASX J23470758＋2926531 has similar abun- dance and star formation properties to NGC 7753, and may be a part of the Arp 86 system.展开更多
We investigate the evolution of nuclear gas-phase oxygen abundance and star formation rate（SFR） of local far-infrared selected star-forming galaxies along the merger sequence, as traced by their optical morphologies...We investigate the evolution of nuclear gas-phase oxygen abundance and star formation rate（SFR） of local far-infrared selected star-forming galaxies along the merger sequence, as traced by their optical morphologies. The sample was drawn from a cross-correlation analysis of the IRAS Point Source Catalog Redshift Survey and 1 Jy ultraluminous infrared galaxy sample with the Sloan Digital Sky Survey Data Release 7 database. The investigation is done by comparing our sample to a control sample matched in the normalized redshift distribution in two diagnostics, which are the nuclear gas-phase metallicity vs.stellar mass and the nuclear SFR vs. stellar mass diagrams. Galaxies with different morphological types show different mass-metallicity relations（MZRs）. Compared to the MZR defined by the control sample,isolated spirals have comparable metallicities with the control sample at a given stellar mass. Spirals in pairs and interacting galaxies with projected separations of rp 〉 20 kpc show a mild metallicity dilution of0.02–0.03 dex. Interacting galaxies with rp 〈 20 kpc, pre-mergers and advanced mergers are underabundant by～0.06,～0.05 and～0.04 dex, respectively. This shows an evolutionary trend that the metallicity is increasingly depressed as the merging proceeds and it is diluted most dramatically when two galaxies are closely interacting. Afterwards, the interstellar medium（ISM） is enriched when the galaxies coalesce.This is the first time that such ISM enrichment at the final coalescence stage has been observed, which demonstrates the importance of supernova explosions in affecting the nuclear metallicity. Moreover, the central SFR enhancement relative to the control sample evolves simultaneously with the nuclear gas-phase oxygen abundance. Our results support the predictions from numerical simulations.展开更多
We select 107 blue-core galaxies from the MaNGA survey, studying their morphology, kinematics as well as the gas-phase metallicity. Our results are as follows:(i) In our sample, 26% of blue-core galaxies have decouple...We select 107 blue-core galaxies from the MaNGA survey, studying their morphology, kinematics as well as the gas-phase metallicity. Our results are as follows:(i) In our sample, 26% of blue-core galaxies have decoupled gas-star kinematics, indicating external gas accretion;15% have bar-like structure and 8% show post-merger features, such as tidal tails and irregular gas/star velocity field. All these processes/features, such as accreting external misaligned gas, interaction and bar, can trigger gas inflow. Thus the central star-forming activities lead to bluer colors in their centers(blue-core galaxies).(ii) By comparing with the SDSS DR7 star-forming galaxy sample, we find that the blue-core galaxies have higher central gas-phase metallicity than what is predicted by the local mass-metallicity relation. We explore the origin of the higher metallicity, finding that not only the blue-core galaxies, but also the flat-gradient and red-core galaxies all have higher metallicity. This can be explained by the combined effect of redshift and galaxy color.展开更多
Using Hurley＇s rapid binary stellar evolution code, we have studied the model-synthesized rate of Type Ia Supernovae （SNe Ia） and its influence on the chemical enrichment of the interstellar medium ejected by stell...Using Hurley＇s rapid binary stellar evolution code, we have studied the model-synthesized rate of Type Ia Supernovae （SNe Ia） and its influence on the chemical enrichment of the interstellar medium ejected by stellar populations. We adopt two popular scenarios, i.e., single degenerate scenario （SD） and double degenerate scenario （DD）, for the progenitors of SNe Ia to calculate the rates of SNe Ia. Rates calculated in this work agree with that of Hachisu et al. and Han ＆ Podsiadlowski, but are different from that usually adopted in chemical evolution models of galaxies. We apply the rates of SNe Ia to the chemical enrichment （especially Fe enrichment）, then compare the results with previous studies. As known SNe Ia slightly affect the enrichment of C, N, O and Mg elements, while significantly affect the enrichment of Fe. We find that the occurrence and the value of the Fe enrichment in our models are earlier and smaller than that commonly adopted in chemical evolution models. We also study the evolution of [Mg/Fe] ratios, which are almost reciprocals of the Fe enrichment. The study may provide constraints on the free parameters of chemical evolution models of galaxies and evolutionary population synthesis.展开更多
利用从斯隆数字巡天（Sloan Digital Sky Survey，简称SDSS）第4次释放的光谱数据中选取的10^5个发射线星系样本，研究了[OII]λ3727／Hα流量比与星系尘埃消光、气体电离态和金属丰度的关系．发现尘埃消光改正对[OII]λ3727／Hα谱线...利用从斯隆数字巡天（Sloan Digital Sky Survey，简称SDSS）第4次释放的光谱数据中选取的10^5个发射线星系样本，研究了[OII]λ3727／Hα流量比与星系尘埃消光、气体电离态和金属丰度的关系．发现尘埃消光改正对[OII]λ3727／Hα谱线流量比影响显著，消光改正前、后的[OII]λ3727／Hα谱线流量比的中值分别为0．48和0．89；尘埃消光改正后，F（[OII]λ3727）-F（Hα）的弥散显著减小．贫金属星系的[OII]λ3727／Hα谱线流量比随星系气体的电离度增高而减小，而富金属星系不存在这种关系．另外，[OII]λ3727／Hα流量比与星系金属丰度相关．当12＋lg（O／H）〉8．5时，星系[OII]λ3727／Hα流量比随金属丰度增加而下降；12＋lg（O／H）〈8．5的星系，谱线流量比与金属丰度正相关．最后，利用气体电离度参数和星系的金属丰度，给出了计算不同类型星系[OII]λ3727／Hα流量比的公式．LAMOST望远镜将观测到大量红移z〉0．4的星系光谱，利用该公式可以给出星系的[OII]λ3727／Hα流量比，从而可以利用[OII]λ3727谱线流量计算z〉0．4星系的恒星形成率．展开更多
By using Data Analysis Pipeline(DAP)products of Mapping Nearby Galaxies at Apache Point Observatory(MaNGA),which are publicly available from the SDSS Data Release 15,we analyze the local properties at the SN explosion...By using Data Analysis Pipeline(DAP)products of Mapping Nearby Galaxies at Apache Point Observatory(MaNGA),which are publicly available from the SDSS Data Release 15,we analyze the local properties at the SN explosion sites and global properties of different types of SN host galaxies to explore the explosion environments of different types of SNe.In our sample,there are 67 SN host galaxies in the field of view of MaNGA,including 32 Type Ia,29 core collapse SNe(CCSNe),1 superluminous SN(SLSN),1 Type I and 4 unclassified type of SNe,with which we can apply the K-S test for analysis and derive statistically robust results.Due to the limited sample size,we could not remove the mass dependence in this work,which is likely the true driver of the trends for the properties presented in this work.The global star formation rate(SFR)and EW(H)for SN Ia hosts are slightly lower than those for CCSN hosts on average.SN Ia host galaxies are0.3 dex more massive than CCSN hosts,which implies that the number ratio of CCSNe to Type Ia SNe will decrease with increasing stellar mass of host galaxies.The stellar population age of SN Ia host galaxies is older than that of CCSN hosts on average.There is no significant difference between different types of SN hosts for some properties,including local SFR density(SFR),and local and global gas-phase oxygen abundance.For most galaxies in our sample,the global gas-phase oxygen abundance estimated from the integrated spectra of SN hosts can represent the local gas-phase oxygen abundance at the SN explosion sites with small bias.展开更多
We study the subhalo and satellite populations in haloes similar to the Milky Way(MW)-Andromeda paired configuration in the Millennium II and P-Millennium simulations.We find subhaloes are 5%–15%more abundant in pair...We study the subhalo and satellite populations in haloes similar to the Milky Way(MW)-Andromeda paired configuration in the Millennium II and P-Millennium simulations.We find subhaloes are 5%–15%more abundant in paired haloes than their isolated counterparts that have the same halo mass and large-scale environmental density.Paired haloes tend to reside in a more isotropic environment than isolated haloes,the shear tensor of their large-scale tidal field is possibly responsible for this difference.We also study the thickness of the spatial distribution of the top 11 most massive satellite galaxies obtained in the semi-analytic galaxy sample constructed from the Millennium II simulation.Moreover,satellites that have lost their host subhaloes due to the resolution limit of the simulation have been taken into account.As a result,we find that the difference in the distribution of the satellite thickness between isolated and paired haloes is indistinguishable,which suggests that the paired configuration is not responsible for the observed plane of satellites in the MW.The results in this study indicate the paired configuration could bring some nonnegligible effect on the subhalo abundance in the investigation of the MW's satellite problems.展开更多
定位快速射电暴(Fast Radio Burst,FRB)以及确认其寄主星系至今仍是一个具有挑战性的难题,截至2021年4月已确认13个快速射电暴的寄主星系,其中只有3个重复暴,其余都是非重复暴.快速射电暴的寄主星系对快速射电暴起源的探索起着非常重要...定位快速射电暴(Fast Radio Burst,FRB)以及确认其寄主星系至今仍是一个具有挑战性的难题,截至2021年4月已确认13个快速射电暴的寄主星系,其中只有3个重复暴,其余都是非重复暴.快速射电暴的寄主星系对快速射电暴起源的探索起着非常重要的作用,约束着快速射电暴前身星模型.对这些已确认寄主星系的FRB进行研究,发现FRB寄主星系对色散量(Dispersion Measure,DM)的贡献在一定范围内波动(0–240 pc·cm^(−3)),并且寄主星系对DM的贡献与寄主星系的性质(恒星形成率、金属丰度)也可能具有关联性.寄主星系恒星形成率、金属丰度与色散量的统计关系对FRB邻近环境的研究有着重要意义.展开更多
We analyze the radial and vertical metallicity and [α/Fe] gradients of the disk stars of a disk galaxy simulated in a fully cosmological setting with the chemo- dynamical galaxy evolution code GCD＋. We study how the...We analyze the radial and vertical metallicity and [α/Fe] gradients of the disk stars of a disk galaxy simulated in a fully cosmological setting with the chemo- dynamical galaxy evolution code GCD＋. We study how the radial abundance gradients vary as a function of height above the plane and find that the metallicity （[α/Fe]） gra- dient becomes more positive （negative） with increasing height, changing sign around 1.5 kpc above the plane. At the largest vertical height （2 〈 丨z丨 〈 3 kpc）, our simulated galaxy shows a positive radial metallicity gradient. We find that the positive metallicity gradient is caused by the age-metallicity and age-velocity dispersion relation, where younger stars have higher metallicity and lower velocity dispersion. Due to the age- velocity dispersion relation, a greater fraction of younger stars reaches 丨z丨 〉 2 kpc at the outer region, because of the lower gravitational restoring force of the disk, i.e. flaring. As a result, the fraction of younger stars with higher metallicity due to the age-metallicity relation becomes higher at the outer radii, which makes the median metallicity higher at the outer radii. Combining this result with the recently observed age-metallicity and age-velocity dispersion relation for the Milky Way thick disk stars suggested by Haywood et al., we argue that the observed （small） positive radial metal- licity gradient at large heights of the Milky Way disk stars can be explained by flaring of the younger thick and/or thin disk stars.展开更多
We enhance the Syer ＆ Tremaine made-to-measure （M2M） particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a ＇chemo-M2M＇ model...We enhance the Syer ＆ Tremaine made-to-measure （M2M） particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a ＇chemo-M2M＇ modelling scheme. We apply the enhanced method to four galaxies （NGC 1248, NGC 3838, NGC 4452, NGC 4551） observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean X2 per bin values of ≈ 1 with 〉 95% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these dis- tributions are plausible representations of real galaxies requires further consideration. Overall, we consider the modelling exercise to be a promising first step in developing a ＇chemo-M2M＇ modelling system and in understanding some of the issues to be addressed. While the made-to-measure techniques developed have been applied to absorption line strength data, they are in fact general and may be of value in modelling other aspects of galaxies.展开更多
We present a sample of 48 metal-poor galaxies at z 〈 0.14 selected from 92 510 galaxies in the LAMOST survey. These galaxies are identified by their detection of the auroral emission line[OⅢ]λ4363 above the 3σ lev...We present a sample of 48 metal-poor galaxies at z 〈 0.14 selected from 92 510 galaxies in the LAMOST survey. These galaxies are identified by their detection of the auroral emission line[OⅢ]λ4363 above the 3σ level, which allows a direct measurement of electron temperature and oxygen abundance. The emission line fluxes are corrected for internal dust extinction using the Balmer decrement method. With electron temperature derived from [OⅢ]λλ4959, 5007/[OⅢ]λ4363 and electron density from [SⅡ]λ6731/[SⅡ]λ6717, we obtain the oxygen abundances in our sample which range from 12 ＋ log（O/H） = 7.63（0.09 Z_⊙） to 8.46（0.6 Z_⊙）. We find an extremely metal-poor galaxy with 12 ＋ log（O/H） = 7.63 ± 0.01. With multiband photometric data from FUV to NIR and Hαmeasurements, we also determine the stellar masses and star formation rates, based on the spectral energy distribution fitting and Hα luminosity, respectively. We find that our galaxies have low and intermediate stellar masses with 6.39 ≤ log（M/M_⊙） ≤ 9.27, and high star formation rates（SFRs） with-2.18 ≤ log（SFR/M_⊙yr^（-1）） ≤ 1.95. We also find that the metallicities of our galaxies are consistent with the local T_e-based mass-metallicity relation, while the scatter is about 0.28 dex. Additionally,assuming the coefficient of α = 0.66, we find most of our galaxies follow the local mass-metallicity-SFR relation, but a scatter of about 0.24 dex exists, suggesting the mass-metallicity relation is weakly dependent on SFR for those metal-poor galaxies.展开更多
We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio o...We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio of the emission in 0.65- 1.4 keV to that in 0.3-0.6 keV and 1.4-3.5 keV （after the magnesium and silicon lines are excluded）, and HRcont as the ratio of the emission in 1.4-3.5keV to that in 0.3- 0.6 keV, so that the HRFeL and HRcont maps can be used to trace the iron abundance and gas temperature distributions, respectively. By applying the a Trous wavelet algorithm to the obtained emission hardness ratio maps, we reveal that the HRFeL distributions are highly irregular, exhibiting strong spatial variations on 0.1-1 Re scales, which do not follow the HRcont distributions. Since the effect of temperature variation is small, we conclude that most of the high-HRFeL regions are very likely to possess higher abundances than the ambient gas. We also find that these high-HRFeL substructures are not associated with either the LMXB or globular cluster populations, thus their origins should be related to AGN activity or mergers.展开更多
基金support from the National Key Research and Development Program of China(2022SKA0130100)the National Natural Science Foundation of China (grant No. 12041306)+1 种基金supported by national funds through Fundacao para a Ciência e a Tecnologia (FCT)the Centro de Astrofísica da Universidade do Porto (CAUP)。
文摘We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9(z = 0.005)(hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy(TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g-r color of 0.23 mag, irregular optical morphology and high-metallicity(12 +log(O/H) = 8.68 ± 0.14), making it an interesting galaxy to study in more detail. We find J2306 to be an H I rich galaxy with a large extended, unperturbed rotating H I disk. Using our H I data we estimated its dynamical mass and found the galaxy to be dark matter(DM) dominated within its H I radius. The quantity of DM, inferred from its dynamical mass, appears to rule out J2306 as an evolved TDG. A wide area environment search reveals J2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the H I morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity.Further detailed optical spectroscopic observations of J2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11733006, 11273026, 11233004 and U1631105)
文摘We aim to understand the properties at the locations of supernova(SN) explosions in their host galaxies and compare with the global properties of these host galaxies. We use the integral field spectrograph(IFS) of Mapping Nearby Galaxies at Apache Point Observatory(MaNGA) to generate 2 D maps of the parameter properties for 11 SN host galaxies. The sample galaxies are analyzed one by one in detail in terms of their properties of velocity field, star formation rate, oxygen abundance, stellar mass, etc.This sample of SN host galaxies has redshifts around z^0.03, which is higher than those of previous related works. The higher redshift distribution allows us to obtain the properties of more distant SN host galaxies. Metallicity(gas-phase oxygen abundance) estimated from integrated spectra can represent the local metallicity at SN explosion sites with small bias. All the host galaxies in our sample are metal-rich galaxies(12+log(O/H)> 8.5) except for NGC 6387, which means SNe may be more inclined to explode in metallicity-rich galaxies. There is a positive relation between global gas-phase oxygen abundance and the stellar mass of host galaxies. We also try to compare the differences of the host galaxies between SNe Ia and SNe II. In our sample, both SNe Ia and SNe II can explode in normal galaxies, but SNe II can also explode in an interacting or a merging system, in which star formation is occurring in the galaxy.
基金partly supported by the National Key Basic Research and Development Program of China (No.2018YFA0404501 to SM)by the National Natural Science Foundation of China (Grant Nos.11333003, 11390372 and 11761131004 to SM)
文摘We extend Schwarzschild’s dynamical modelling method to model absorption line strength data as well as the more usual luminosity and kinematic data.Our approach draws on earlier published work by the first author with the Syer & Tremaine made-to-measure(M2M) dynamical modelling method and uses similar ideas to create a chemo-Schwarzschild method.We apply our extended Schwarzschild method to the same four early type galaxies(NGC 1248, NGC 3838, NGC 4452,NGC 4551) as the chemo-M2M work, and are able to recover successfully the 2D absorption line strength for the three lines we model(Hβ, Fe5015, Mg b).We believe that this is the first time Schwarzschild’s method has been used in this way.The techniques developed can be applied to modelling other aspects of galaxies, for example age and metallicity data coming from stellar population modelling, and are not specific to absorption line strength data.
基金supported by the National SKA Program of China No.2020SKA0110402the National Natural Science Foundationof China(NSFC)under grant No.12073088the National Key R&D Program of China(grant No.2020YFC2201600)。
文摘The overabundance of the red and massive candidate galaxies observed by the James Webb Space Telescope(JWST)implies efficient structure formation or large star formation efficiency at high redshift z~10.In the scenario of a low or moderate star formation efficiency,because massive neutrinos tend to suppress the growth of structure of the universe,the JWST observation tightens the upper bound of the neutrino masses.Assuming A cold dark matter cosmology and a star formation efficiency∈[0.05,0.3](flat prior),we perform joint analyses of Planck+JWST and Planck+BAO+JWST,and obtain improved constraints∑m_(ν)<0.196 eV and ∑m_(ν)+<0.111 eV at 95% confidence level,respectively.Based on the above assumptions,the inverted mass ordering,which implies ∑m_(ν)≥0.1 eV,is excluded by Planck+BAO+JWST at 92.7% confidence level.
基金Supported by the National Natural Science Foundation of China
文摘We present an analysis of the metallicity and star formation activities of H II regions in the interacting system Arp 86, based on the first scientific observations using mulri-object spectroscopy with the 2.16 m telescope at the Xinglong Observing Station. We find that the oxygen abundance gradient in Arp 86 is flatter than that in normal disk galaxies, which confirms that gas inflows caused by tidal forces during encounters can flatten the metallicity distributions in galaxies. The companion galaxy NGC 7752 is currently experiencing a galaxy-wide starburst with a higher star for- marion rate surface density than the main galaxy NGC 7753, which can be explained in that the companion galaxy is more susceptible to the effects of interaction than the primary. We also find that the galaxy 2MASX J23470758＋2926531 has similar abun- dance and star formation properties to NGC 7753, and may be a part of the Arp 86 system.
基金supported by the National Natural Science Foundation of China(Grant Nos.11373027 and11003015)SRF for ROCS,SEM.Funding for the creation and distribution of the SDSS Archive has been provided by the Alfred P.Sloan Foundation,the Participating Institutions,the National Aeronautics and Space Administration,the National Science Foundation,the U.S.Department of Energy,the Japanese Monbukagakusho,and the Max Planck Society
文摘We investigate the evolution of nuclear gas-phase oxygen abundance and star formation rate（SFR） of local far-infrared selected star-forming galaxies along the merger sequence, as traced by their optical morphologies. The sample was drawn from a cross-correlation analysis of the IRAS Point Source Catalog Redshift Survey and 1 Jy ultraluminous infrared galaxy sample with the Sloan Digital Sky Survey Data Release 7 database. The investigation is done by comparing our sample to a control sample matched in the normalized redshift distribution in two diagnostics, which are the nuclear gas-phase metallicity vs.stellar mass and the nuclear SFR vs. stellar mass diagrams. Galaxies with different morphological types show different mass-metallicity relations（MZRs）. Compared to the MZR defined by the control sample,isolated spirals have comparable metallicities with the control sample at a given stellar mass. Spirals in pairs and interacting galaxies with projected separations of rp 〉 20 kpc show a mild metallicity dilution of0.02–0.03 dex. Interacting galaxies with rp 〈 20 kpc, pre-mergers and advanced mergers are underabundant by～0.06,～0.05 and～0.04 dex, respectively. This shows an evolutionary trend that the metallicity is increasingly depressed as the merging proceeds and it is diluted most dramatically when two galaxies are closely interacting. Afterwards, the interstellar medium（ISM） is enriched when the galaxies coalesce.This is the first time that such ISM enrichment at the final coalescence stage has been observed, which demonstrates the importance of supernova explosions in affecting the nuclear metallicity. Moreover, the central SFR enhancement relative to the control sample evolves simultaneously with the nuclear gas-phase oxygen abundance. Our results support the predictions from numerical simulations.
基金supported by the National Key R&D Program of China (2018YFA0404502 and 2017YFA0402704)the National Natural Science Foundation of China (Grant Nos. 11733002 and 11773013)+1 种基金the Excellent Youth Foundation of the Jiangsu Scientific Committee (BK 20150014)the National Natural Science Foundation of China (Grant No. 11573013)
文摘We select 107 blue-core galaxies from the MaNGA survey, studying their morphology, kinematics as well as the gas-phase metallicity. Our results are as follows:(i) In our sample, 26% of blue-core galaxies have decoupled gas-star kinematics, indicating external gas accretion;15% have bar-like structure and 8% show post-merger features, such as tidal tails and irregular gas/star velocity field. All these processes/features, such as accreting external misaligned gas, interaction and bar, can trigger gas inflow. Thus the central star-forming activities lead to bluer colors in their centers(blue-core galaxies).(ii) By comparing with the SDSS DR7 star-forming galaxy sample, we find that the blue-core galaxies have higher central gas-phase metallicity than what is predicted by the local mass-metallicity relation. We explore the origin of the higher metallicity, finding that not only the blue-core galaxies, but also the flat-gradient and red-core galaxies all have higher metallicity. This can be explained by the combined effect of redshift and galaxy color.
基金Supported by the National Natural Science Foundation of China.
文摘Using Hurley＇s rapid binary stellar evolution code, we have studied the model-synthesized rate of Type Ia Supernovae （SNe Ia） and its influence on the chemical enrichment of the interstellar medium ejected by stellar populations. We adopt two popular scenarios, i.e., single degenerate scenario （SD） and double degenerate scenario （DD）, for the progenitors of SNe Ia to calculate the rates of SNe Ia. Rates calculated in this work agree with that of Hachisu et al. and Han ＆ Podsiadlowski, but are different from that usually adopted in chemical evolution models of galaxies. We apply the rates of SNe Ia to the chemical enrichment （especially Fe enrichment）, then compare the results with previous studies. As known SNe Ia slightly affect the enrichment of C, N, O and Mg elements, while significantly affect the enrichment of Fe. We find that the occurrence and the value of the Fe enrichment in our models are earlier and smaller than that commonly adopted in chemical evolution models. We also study the evolution of [Mg/Fe] ratios, which are almost reciprocals of the Fe enrichment. The study may provide constraints on the free parameters of chemical evolution models of galaxies and evolutionary population synthesis.
文摘利用从斯隆数字巡天（Sloan Digital Sky Survey，简称SDSS）第4次释放的光谱数据中选取的10^5个发射线星系样本，研究了[OII]λ3727／Hα流量比与星系尘埃消光、气体电离态和金属丰度的关系．发现尘埃消光改正对[OII]λ3727／Hα谱线流量比影响显著，消光改正前、后的[OII]λ3727／Hα谱线流量比的中值分别为0．48和0．89；尘埃消光改正后，F（[OII]λ3727）-F（Hα）的弥散显著减小．贫金属星系的[OII]λ3727／Hα谱线流量比随星系气体的电离度增高而减小，而富金属星系不存在这种关系．另外，[OII]λ3727／Hα流量比与星系金属丰度相关．当12＋lg（O／H）〉8．5时，星系[OII]λ3727／Hα流量比随金属丰度增加而下降；12＋lg（O／H）〈8．5的星系，谱线流量比与金属丰度正相关．最后，利用气体电离度参数和星系的金属丰度，给出了计算不同类型星系[OII]λ3727／Hα流量比的公式．LAMOST望远镜将观测到大量红移z〉0．4的星系光谱，利用该公式可以给出星系的[OII]λ3727／Hα流量比，从而可以利用[OII]λ3727谱线流量计算z〉0．4星系的恒星形成率．
基金the National Science Foundation of China(Grant No.11733006 to HW,11903046 to JG and U1631105 to WB)the Beijing Municipal Natural Science Foundation(No.1204038 to JG).
文摘By using Data Analysis Pipeline(DAP)products of Mapping Nearby Galaxies at Apache Point Observatory(MaNGA),which are publicly available from the SDSS Data Release 15,we analyze the local properties at the SN explosion sites and global properties of different types of SN host galaxies to explore the explosion environments of different types of SNe.In our sample,there are 67 SN host galaxies in the field of view of MaNGA,including 32 Type Ia,29 core collapse SNe(CCSNe),1 superluminous SN(SLSN),1 Type I and 4 unclassified type of SNe,with which we can apply the K-S test for analysis and derive statistically robust results.Due to the limited sample size,we could not remove the mass dependence in this work,which is likely the true driver of the trends for the properties presented in this work.The global star formation rate(SFR)and EW(H)for SN Ia hosts are slightly lower than those for CCSN hosts on average.SN Ia host galaxies are0.3 dex more massive than CCSN hosts,which implies that the number ratio of CCSNe to Type Ia SNe will decrease with increasing stellar mass of host galaxies.The stellar population age of SN Ia host galaxies is older than that of CCSN hosts on average.There is no significant difference between different types of SN hosts for some properties,including local SFR density(SFR),and local and global gas-phase oxygen abundance.For most galaxies in our sample,the global gas-phase oxygen abundance estimated from the integrated spectra of SN hosts can represent the local gas-phase oxygen abundance at the SN explosion sites with small bias.
基金supported by the National Key R&D Program of China(Nos.2018YFE0202900 and 2022YFA1602901)by the NSFC Grant(Nos.11988101,11873051,12125302 and 12273053)+6 种基金support from the K.C.Wong Education Foundationthe support of CAS Project for Young Scientists in Basic Research,grant No.YSBR-062the science research grants from the China Manned Spaced Project with No.CMS-CSST-2021-B03the support of the National Natural Science Foundation of China(Nos.12047569 and 12147217)the Natural Science Foundation of Jilin Province,China(No.20180101228JC)funded by BIS National E-infrastructure capital grant ST/K00042X/1,STFC capital grant ST/H008519/1STFC Di RAC Operations grant ST/K003267/1 and Durham University。
文摘We study the subhalo and satellite populations in haloes similar to the Milky Way(MW)-Andromeda paired configuration in the Millennium II and P-Millennium simulations.We find subhaloes are 5%–15%more abundant in paired haloes than their isolated counterparts that have the same halo mass and large-scale environmental density.Paired haloes tend to reside in a more isotropic environment than isolated haloes,the shear tensor of their large-scale tidal field is possibly responsible for this difference.We also study the thickness of the spatial distribution of the top 11 most massive satellite galaxies obtained in the semi-analytic galaxy sample constructed from the Millennium II simulation.Moreover,satellites that have lost their host subhaloes due to the resolution limit of the simulation have been taken into account.As a result,we find that the difference in the distribution of the satellite thickness between isolated and paired haloes is indistinguishable,which suggests that the paired configuration is not responsible for the observed plane of satellites in the MW.The results in this study indicate the paired configuration could bring some nonnegligible effect on the subhalo abundance in the investigation of the MW's satellite problems.
文摘定位快速射电暴(Fast Radio Burst,FRB)以及确认其寄主星系至今仍是一个具有挑战性的难题,截至2021年4月已确认13个快速射电暴的寄主星系,其中只有3个重复暴,其余都是非重复暴.快速射电暴的寄主星系对快速射电暴起源的探索起着非常重要的作用,约束着快速射电暴前身星模型.对这些已确认寄主星系的FRB进行研究,发现FRB寄主星系对色散量(Dispersion Measure,DM)的贡献在一定范围内波动(0–240 pc·cm^(−3)),并且寄主星系对DM的贡献与寄主星系的性质(恒星形成率、金属丰度)也可能具有关联性.寄主星系恒星形成率、金属丰度与色散量的统计关系对FRB邻近环境的研究有着重要意义.
基金Supported by the National Natural Science Foundation of China
文摘We analyze the radial and vertical metallicity and [α/Fe] gradients of the disk stars of a disk galaxy simulated in a fully cosmological setting with the chemo- dynamical galaxy evolution code GCD＋. We study how the radial abundance gradients vary as a function of height above the plane and find that the metallicity （[α/Fe]） gra- dient becomes more positive （negative） with increasing height, changing sign around 1.5 kpc above the plane. At the largest vertical height （2 〈 丨z丨 〈 3 kpc）, our simulated galaxy shows a positive radial metallicity gradient. We find that the positive metallicity gradient is caused by the age-metallicity and age-velocity dispersion relation, where younger stars have higher metallicity and lower velocity dispersion. Due to the age- velocity dispersion relation, a greater fraction of younger stars reaches 丨z丨 〉 2 kpc at the outer region, because of the lower gravitational restoring force of the disk, i.e. flaring. As a result, the fraction of younger stars with higher metallicity due to the age-metallicity relation becomes higher at the outer radii, which makes the median metallicity higher at the outer radii. Combining this result with the recently observed age-metallicity and age-velocity dispersion relation for the Milky Way thick disk stars suggested by Haywood et al., we argue that the observed （small） positive radial metal- licity gradient at large heights of the Milky Way disk stars can be explained by flaring of the younger thick and/or thin disk stars.
基金supported by the Strategic Priority Research Program“The Emergence of Cosmological Structures”of the Chinese Academy of Sciences(Grant No.XDB09000000)by the National Natural Science Foundation of China(NSFC,Grant Nos.11333003 and 11390372).
文摘We enhance the Syer ＆ Tremaine made-to-measure （M2M） particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a ＇chemo-M2M＇ modelling scheme. We apply the enhanced method to four galaxies （NGC 1248, NGC 3838, NGC 4452, NGC 4551） observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean X2 per bin values of ≈ 1 with 〉 95% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these dis- tributions are plausible representations of real galaxies requires further consideration. Overall, we consider the modelling exercise to be a promising first step in developing a ＇chemo-M2M＇ modelling system and in understanding some of the issues to be addressed. While the made-to-measure techniques developed have been applied to absorption line strength data, they are in fact general and may be of value in modelling other aspects of galaxies.
基金Funding for the project has been provided by the National Development and Reform Commissionsupported by the Strategic Priority Research Program “The Emergence of Cosmological Structures” of the Chinese Academy of Sciences (No. XDB09000000)+1 种基金the National Basic Research Program of China (973 Program) (2015CB857004)the National Natural Science Foundation of China (NSFC, Nos. 11225315, 1320101002, 11433005 and 11421303)
文摘We present a sample of 48 metal-poor galaxies at z 〈 0.14 selected from 92 510 galaxies in the LAMOST survey. These galaxies are identified by their detection of the auroral emission line[OⅢ]λ4363 above the 3σ level, which allows a direct measurement of electron temperature and oxygen abundance. The emission line fluxes are corrected for internal dust extinction using the Balmer decrement method. With electron temperature derived from [OⅢ]λλ4959, 5007/[OⅢ]λ4363 and electron density from [SⅡ]λ6731/[SⅡ]λ6717, we obtain the oxygen abundances in our sample which range from 12 ＋ log（O/H） = 7.63（0.09 Z_⊙） to 8.46（0.6 Z_⊙）. We find an extremely metal-poor galaxy with 12 ＋ log（O/H） = 7.63 ± 0.01. With multiband photometric data from FUV to NIR and Hαmeasurements, we also determine the stellar masses and star formation rates, based on the spectral energy distribution fitting and Hα luminosity, respectively. We find that our galaxies have low and intermediate stellar masses with 6.39 ≤ log（M/M_⊙） ≤ 9.27, and high star formation rates（SFRs） with-2.18 ≤ log（SFR/M_⊙yr^（-1）） ≤ 1.95. We also find that the metallicities of our galaxies are consistent with the local T_e-based mass-metallicity relation, while the scatter is about 0.28 dex. Additionally,assuming the coefficient of α = 0.66, we find most of our galaxies follow the local mass-metallicity-SFR relation, but a scatter of about 0.24 dex exists, suggesting the mass-metallicity relation is weakly dependent on SFR for those metal-poor galaxies.
基金supported by the National Natural Science Foundation of China(Grant Nos.10503008,10673008,10878001 and 10973010)the Ministry of Science and Technology of China(Grant No.2009CB824900/2009CB24904)the Ministry of Education of China(the NCET Program)
文摘We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio of the emission in 0.65- 1.4 keV to that in 0.3-0.6 keV and 1.4-3.5 keV （after the magnesium and silicon lines are excluded）, and HRcont as the ratio of the emission in 1.4-3.5keV to that in 0.3- 0.6 keV, so that the HRFeL and HRcont maps can be used to trace the iron abundance and gas temperature distributions, respectively. By applying the a Trous wavelet algorithm to the obtained emission hardness ratio maps, we reveal that the HRFeL distributions are highly irregular, exhibiting strong spatial variations on 0.1-1 Re scales, which do not follow the HRcont distributions. Since the effect of temperature variation is small, we conclude that most of the high-HRFeL regions are very likely to possess higher abundances than the ambient gas. We also find that these high-HRFeL substructures are not associated with either the LMXB or globular cluster populations, thus their origins should be related to AGN activity or mergers.
