Using a semi-analytic approach,we estimate halo spins for a large sample of H I-rich galaxies from the Arecibo Legacy Fast ALFA Survey and examine the correlation between H I mass fractions and halo spins.Our analysis...Using a semi-analytic approach,we estimate halo spins for a large sample of H I-rich galaxies from the Arecibo Legacy Fast ALFA Survey and examine the correlation between H I mass fractions and halo spins.Our analysis reveals a strong correlation between halo spin and the H I-to-stellar mass ratio in both low-mass and massive galaxy samples.This finding suggests a universal formation scenario:higher halo spin reduces angular momentum loss and gas condensation,leading to lower star formation rates and weaker feedback,which in turn help retain gas within dark matter halos.展开更多
This study examines the properties of standard cold dark matter(CDM),fuzzy dark matter(FDM),and selfinteracting dark matter(SIDM)haloes by analyzing the rotation curves of selected dwarf galaxies from SPARC and LITTLE...This study examines the properties of standard cold dark matter(CDM),fuzzy dark matter(FDM),and selfinteracting dark matter(SIDM)haloes by analyzing the rotation curves of selected dwarf galaxies from SPARC and LITTLE THINGS in 3D catalogs.Utilizing the Markov Chain Monte Carlo(MCMC)method for model fitting and Bayesian Information Criterion for model comparison,we find that compared to CDM,both FDM and SIDM haloes generally provide better fits to the observed rotation curves.Our findings reveal that the concentration–mass relation derived from the dark matter-only simulations is not followed by concentrations or masses obtained from the rotation curve data.Our analysis highlights a positive correlation between the core sizes of FDM and SIDM haloes and the effective radius of the galaxy,attributable to gravitational couplings between baryonic and dark matter components.Moreover,our exploration of dark matter fractions at characteristic radii indicates considerable diversity in dark matter distributions across dwarf galaxies.Notably,FDM and SIDM exhibit greater diversity than CDM in this respect.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
We investigate the small-scale clustering of star-forming galaxies(SFGs) in the local universe, using both observational samples from the final data release of the Sloan Digital Sky Survey and IllustrisTNG300, one of ...We investigate the small-scale clustering of star-forming galaxies(SFGs) in the local universe, using both observational samples from the final data release of the Sloan Digital Sky Survey and IllustrisTNG300, one of the state-of-the-art hydrodynamic simulations of galaxy formation. We measure the projected two-point crosscorrelation function, wp(rp), for subsamples of SFGs with different specific star formation rates(sSFRs) and stellar masses(M*), with respect to reference samples of galaxies with early-type or late-type morphology. On scales smaller than ~100 kpc and at fixed M*, SFGs with higher sSFR are more strongly clustered, reflecting the interaction-induced central star formation found in previous studies. More importantly, the small-scale clusteringsSFR correlation is stronger when the reference sample is limited to late-type galaxies only. This confirms the previous finding that the enhancement of star formation in close pairs depends on the morphology of companion galaxies. These observational trends are broadly reproduced by IllustrisTNG300, indicating that current hydrodynamic simulations are capable of capturing the main recipes governing star formation in interacting/merging galaxies, although further work is needed to identify the exact physical processes involved.展开更多
Leveraging the semi-analytic method,we compute halo spins for a substantial sample of H I-bearing galaxies observed in the Arecibo Legacy Fast ALFA Survey.Our statistical analysis reveals a correlation between halo sp...Leveraging the semi-analytic method,we compute halo spins for a substantial sample of H I-bearing galaxies observed in the Arecibo Legacy Fast ALFA Survey.Our statistical analysis reveals a correlation between halo spin and environment,although the trend is subtle.On average,galaxies exhibit a decreasing halo spin tendency in denser environments.This observation contrasts with previous results from N-body simulations in the Lambda Cold Dark Matter framework.The discrepancy may be attributed to environmental gas stripping,leading to an underestimation of halo spins in galaxies in denser environments,or to baryonic processes that significantly alter the original dark matter halo spins,deviating from previous N-body simulation findings.展开更多
We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic index n<2) in a loca close major-merger galaxy pair sample (H-KPAIR).With data from new aperture photometries in the opt...We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic index n<2) in a loca close major-merger galaxy pair sample (H-KPAIR).With data from new aperture photometries in the optical and near-infrared bands (aperture size of 7 kpc) and from the literature,we find that the mean Age of central stellar populations in Spirals with pseudobulges is consistent with that of disky galaxies and is nearly constant against the bulge-to-total ratio (B/T).Paired Spirals have a slightly lower fraction of pure disk galaxies (B/T≤0.1) than their counterparts in the control sample.Compared to SFGs with classical bulges,those with pseudobulges have a higher (>2σ) mean of specific star formation rate (sSFR) enhancement (sSFR_(enh)=0.33±0.07 versus sSFR_(enh)=0.12±0.06) and broader scatter (by~1 dex).The eight SFGs that have the highest sSFR_(enh)in the sample all have pseudobulges.A majority (69%) of paired SFGs with strong enhancement (having sSFR more than5 times the median of the control galaxies) have pseudobulges.The Spitzer data show that the pseudobulges in these galaxies are tightly linked to nuclear/circum-nuclear starbursts.Pseudobulge SFGs in S+S and in S+E pairs have significantly (>3σ) different sSFR enhancement,with the means of sSFR_(enh)=0.45±0.08 and-0.04±0.11respectively.We find a decrease in the sSFR enhancements with the density of the environment for SFGs with pseudobulges.Since a high fraction (5/11) of pseudobulge SFGs in S+E pairs are in rich groups/clusters (loca density N_(1Mpc)≥7),the dense environment might be the cause for their low s SFR_(enh).展开更多
Slitless spectroscopy onboard space telescopes is a powerful tool to detect emission-line objects such as emissionline galaxies(ELGs)and quasars.In this work,we present a study of ELGs observed with slitless spectrosc...Slitless spectroscopy onboard space telescopes is a powerful tool to detect emission-line objects such as emissionline galaxies(ELGs)and quasars.In this work,we present a study of ELGs observed with slitless spectroscopy by the Hubble Space Telescope(HST)in a deep field of~44 arcmin^(2).This is one of the deepest HST fields with a wealth of imaging and spectral data.In particular,previous VLT/MUSE observations have covered this field and identified a large number of ELGs.We reduce the HST spectra using the latest pipeline with a forward modeling algorithm and construct a sample of ELGs.By comparing with the MUSE spectra,we characterize our ELG detection in the HST spectra,including the impact of the line flux,line width,signal-to-noise ratio,etc.We find that the morphological broadening may affect the detection of ELGs,such that more compact sources are easier to be detected in slitless spectra.We discuss its implications to future slitless spectroscopic surveys that will be carried out by the China Space Station Telescope(CSST)and find that the CSST slitless spectroscopy has a capability comparable to that of HST in terms of the detection of emission lines.展开更多
This paper presents a statistical study of the division of the[CⅡ]158μm line into ionized and neutral components,using a new carbon-to-nitrogen abundance ratio,log(C/N)=0.75,for a sample of 108 local galaxies.We inv...This paper presents a statistical study of the division of the[CⅡ]158μm line into ionized and neutral components,using a new carbon-to-nitrogen abundance ratio,log(C/N)=0.75,for a sample of 108 local galaxies.We investigate the correlation between the ionized-to-total[CⅡ]ratio([CⅡ]_(ionized)/[CⅡ]_(total))and the farinfrared color f60/f100,finding a moderate negative correlation.Additionally,we explore the dependence of[CⅡ]_(ionized)/[CⅡ]_(total)on various physical properties.We find that[CⅡ]_(ionized)/[CⅡ]_(total)exhibits a weak negative correlation with the offset from the main sequence and a moderate negative correlation with the[OⅢ]88μm/[NⅡ]122μm.Furthermore,no significant correlation with molecular gas mass is found.It shows a positive correlation with metallicity.Our results suggest that[CⅡ]_(ionized)/[CⅡ]_(total)is influenced by the ionization parameter,star formation efficiency and metallicity.展开更多
We present the morphological study of 18,572 massive quiescent galaxies at z~1.2, selected by i-y colors in the Hyper Suprime-Cam(HSC) Deep and UltraDeep fields. The majority of our sample(94.3%) fall in the quiescent...We present the morphological study of 18,572 massive quiescent galaxies at z~1.2, selected by i-y colors in the Hyper Suprime-Cam(HSC) Deep and UltraDeep fields. The majority of our sample(94.3%) fall in the quiescent region in the rest-frame UVJ diagram. Comparing the five HSC bands and the subsample with HST F160W images, consistent with the decreasing effective radius re, Sérsic index n shows an increasing trend indicating a more bulge-dominant morphology towards the infrared. Even for our massive, quiescent galaxies,which are dominated by typical elliptical galaxies with bulges, the reand n values still vary with the wavelengths.For instance, there is a systematic drop in n of ~0.4 going from y band to F160W, making 20% of the HSC “disklike” galaxies appear “bulge-like” in the HST images. We suggest to use caution when comparing galaxy morphological types based on images at different resolutions or at different wavelengths, and whenever possible,to apply a reor n correction. More massive quiescent galaxies are systematically larger than the less massive ones,though no mass dependence is found for n measurements. The size–mass relation based on our sample and lowerz control samples show a monotonic increase of rewith M*, with a power-law of 0.61 ± 0.01, lower than previously found in similar samples of smaller sizes. Future high-resolution space-based surveys like NGRST will help confirm the possible n evolution, and if the flattening at the low-mass end is a genuine physical trend or limited by the image resolutions.展开更多
With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,s...With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,specifically AndromedaⅡ,NGC 205,and NGC 185.Initially,three drift scans were executed for these satellites,with a detection limit of 4×10^(18)cm^(-2)(approximately 1.88×10^(3)M_Θof HⅠmass),followed by a more in-depth scan of a specific region.We discovered a C-shaped HⅠarc structure sharing a position and line-of-sight velocity similar to a stellar ring structure around AndromedaⅡ,hinting at a potential connection with AndromedaⅡ.In the context of NGC 205,we identified two mass concentrations in the northeast direction,which could be indicative of tidal streams resulting from the interaction between this galaxy and M31.These new lumps discovered could be very helpful in solving the missing interstellar medium problem for NGC 205.Observations regarding NGC 185are consistent with previous studies,and we did not detect any additional HⅠmaterial around this galaxy.These observational results enhance our understanding of the evolution of these satellite galaxies and provide insight into their historical interactions with the galaxy M31.展开更多
The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark ...The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(La GRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known La GRLs,we confirm the correlation between radio power P_(1.4GHz)and stellar mass M_(*)of host galaxies.Most(25/35)La GRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P_(1.4GHz)-M_(*)relation,and the galaxy color,indicating that bluer galaxies at a fixed M_(*)tend to host more powerful radio lobes.Furthermore,the majority(31/36)of La GRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.展开更多
Superthin galaxies are observed to have stellar disks with extremely small minor-to-major axis ratios.In this work,we investigate the formation of superthin galaxies in the TNG100 simulation.We trace the merger histor...Superthin galaxies are observed to have stellar disks with extremely small minor-to-major axis ratios.In this work,we investigate the formation of superthin galaxies in the TNG100 simulation.We trace the merger history and investigate the evolution of galaxy properties of a selected sample of superthin galaxies and a control sample of galaxies that share the same joint probability distribution in the stellar-mass and color diagram.Through making comparisons between the two galaxy samples,we find that present-day superthin galaxies had similar morphologies as the control sample counterparts at higher redshifts,but have developed extended flat“superthin”morphologies since z~1.During this latter evolution stage,superthin galaxies undergo an overwhelmingly higher frequency of prograde mergers(with orbit-spin angleθ_(orb)≤40°).Accordingly the spins of their dark matter halos have grown significantly and become noticeably higher than those of their normal disk counterparts.This further results in the buildup of their stellar disks at larger distances much beyond the regimes of normal disk galaxies.We also discuss the formation scenario of those superthin galaxies that live in larger dark matter halos as satellite galaxies therein.展开更多
The coevolution between supermassive black holes(SMBHs) and their host galaxies has been proposed for more than a decade,albeit with little direct evidence about black hole accretion activities regulating galaxy star ...The coevolution between supermassive black holes(SMBHs) and their host galaxies has been proposed for more than a decade,albeit with little direct evidence about black hole accretion activities regulating galaxy star formation at z> 1.In this paper,we study the lifetimes of X-ray active galactic nuclei(AGNs) in UV-selected red sequence(RS),blue cloud(BC) and green valley(GV) galaxies,finding that AGN accretion activities are most prominent in GV galaxies at z ~1.5-2,compared with RS and BC galaxies.We also compare AGN accretion timescales with typical color transition timescales of UV-selected galaxies.We find that the lifetime of GV galaxies at z~1.5-2 is very close to the typical timescale when the AGNs residing in them stay in the high-accretion-rate mode at these redshifts;for BC galaxies,the consistency between the color transition timescale and the black hole strong accretion lifetime is more likely to happen at lower redshifts(z <1).Our results support the scenario where AGN accretion activities govern UV color transitions of host galaxies,making galaxies and their central SMBHs coevolve with each other.展开更多
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
In this paper,we study the rotation curves of the Milky Way galaxy and Andromeda galaxy(M31)by considering their bulge,disk,and halo components.We model the bulge region by the widely accepted de Vaucouleur’s law and...In this paper,we study the rotation curves of the Milky Way galaxy and Andromeda galaxy(M31)by considering their bulge,disk,and halo components.We model the bulge region by the widely accepted de Vaucouleur’s law and the disk region by the well established exponential profile.In order to understand the distribution of dark matter in the halo region,we consider three different dark matter profiles in the framework of the standardΛCDM model namely,Navarro-Frenk-White(NFW),Hernquist and Einasto profiles.We use recent data sets of rotation curves of the Milky Way and Andromeda galaxy.The data consist of rotation velocities of the stars and gas in the galaxy as a function of the radial distance from the center.Using Bayesian statistics,we perform an overall fit including all the components,i.e.,bulge,disk and halo with the data.Our results indicate that the NFW and Hernquist profiles are in concordance with the observational data points.However,the Einasto profile poorly explains the behavior of dark matter in both the galaxies.展开更多
This study introduces a novel convolutional neural network,the WISE Galaxy Classification Network(WGC),for classifying spiral and elliptical galaxies using Wide-field Infrared Survey Explorer(WISE)images.WGC attains a...This study introduces a novel convolutional neural network,the WISE Galaxy Classification Network(WGC),for classifying spiral and elliptical galaxies using Wide-field Infrared Survey Explorer(WISE)images.WGC attains an accuracy of 89.03%,surpassing the combined use of K-means or SVM with the Color-Color method in more accurately identifying galaxy morphologies.The enhanced variant,WGC_mag,integrates magnitude parameters with image features,further boosting the accuracy to 89.89%.The research also delves into the criteria for galaxy classification,discovering that WGC primarily categorizes dust-rich images as elliptical galaxies,corresponding to their lower star formation rates,and classifies less dusty images as spiral galaxies.The paper explores the consistency and complementarity of WISE infrared images with SDSS optical images in galaxy morphology classification.The SDSS Galaxy Classification Network(SGC),trained on SDSS images,achieved an accuracy of 94.64%.The accuracy reached 99.30% when predictions from SGC and WGC were consistent.Leveraging the complementarity of features in WISE and SDSS images,a novel variant of a classifier,namely the Multi-band Galaxy Morphology Integrated Classifier,has been developed.This classifier elevates the overall prediction accuracy to 95.39%.Lastly,the versatility of WGC was validated in other data sets.On the HyperLEDA data set,the distinction between elliptical galaxies and Sc,Scd and Sd spiral galaxies was most pronounced,achieving an accuracy of 90%,surpassing the classification results of the Galaxy Zoo 2 labeled WISE data set.This research not only demonstrates the effectiveness of WISE images in galaxy morphology classification but also represents an attempt to integrate multi-band astronomical data to enhance understanding of galaxy structures and evolution.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
A corotation radius is a key characteristic of disk galaxies that is essential to determine the angular speed of the spiral structureΩ_p,and therefore understand its nature.In the literature,there are plenty of metho...A corotation radius is a key characteristic of disk galaxies that is essential to determine the angular speed of the spiral structureΩ_p,and therefore understand its nature.In the literature,there are plenty of methods to estimate this value,but do these measurements have any consistency?In this work,we collected a data set of corotation radius measurements for 547 galaxies,300 of which had at least two values.An initial analysis reveals that most objects have rather inconsistent corotation radius positions.Moreover,a significant fraction of galactic disks is distinguished by a large error coverage and almost uniform distribution of measurements.These findings do not have any relation to spiral type,Hubble classification,or presence of a bar.Among other reasons,obtained results could be explained by the transient nature of spirals in a considerable part of galaxies.We have made our collected data sample publicly available,and have demonstrated on one example how it could be useful for future research by investigating a winding time value for a sample of galaxies with possible multiple spiral arm patterns.展开更多
In this paper we investigate the stellar populations and star formation histories of 235 active galactic nucleus(AGN)-host dwarf galaxies,consisting of four samples identified separately with different methods(i.e.,ra...In this paper we investigate the stellar populations and star formation histories of 235 active galactic nucleus(AGN)-host dwarf galaxies,consisting of four samples identified separately with different methods(i.e.,radio,X-ray,mid-IR and variability),utilizing the synthesis code STARLIGHT and spectra from the Sloan Digital Sky Survey Data Release 8.Our results show that the variability sample is the oldest,while the mid-IR sample is the youngest,for which the luminosity at 4020?is dominated(>50%)by the young population(t<10~8yr).The light-weighted mean stellar age of the whole sample is in general about 0.7 dex younger than the optical sample studied in Cai et al.We compare the population results between fitting models with and without a power-law(PL)component and find that the neglect of a PL component would lead to an under-and over-estimation by 0.2 and0.1 dex for the light-and mass-weighted mean stellar age,respectively,for our sample of dwarf galaxies,which has a mean fractional contribution of~16%from the AGN.In addition,we obtain further evidence for a possible suppression of star formation in the host galaxy by the central AGN.We also find that there exists an anticorrelation between the extinction-corrected[O III]luminosity and light-weighted mean stellar age,confirming our previous finding that there is a physical connection between AGN and star-forming activities in AGN-host dwarfs.展开更多
Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming inter...Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming interstellar medium(ISM)has relied on heuristic sub-grid models.However,recent high-resolution simulations of the ISM that directly resolve the regulation of star formation suggest different mean relations for the dependences of pressure and star formation rate on the average gas density.In this study,we adopt such a modern,physically grounded parameterization inspired by the TIGRESS small-scale simulations.We dub this model TEQS and use it for a detailed comparative analysis of the formation and evolution of a Milky Way-sized galaxy when compared with the widely used TNG model.By employing high-resolution simulations in tall box setups,we first investigate the structural differences expected for these two models when applied to different self-gravitating gas surface densities.Our results indicate that TEQS produces considerably thinner gaseous layers and can be expected to form stellar distributions with smaller scale-height than TNG,especially at higher surface density.To test whether this induces systematic structural differences in cosmological galaxy formation simulations,we carry out zoom-in simulations of 12 galaxies taken from the set of Milky Way-sized galaxies that have been studied in the Auriga project.Comparing results for these galaxies shows that disk galaxies formed with the TEQS model have on average very similar stellar mass but are more concentrated in their central regions and exhibit smaller stellar radii compared to those formed with the TNG model.The differences in the scale-heights of the formed stellar disks are only marginal,however,suggesting that other factors for setting the thickness of the disk are more important than the applied ISM equation-of-state model.Overall,the predicted galaxy structure is quite similar for TNG and TEQS despite significant differences in the employed star formation law,demonstrating that feedback processes are more important in regulating the stellar mass than the precise star formation law itself.展开更多
基金support from the National Natural Science Foundation of China(NSFC)grant 12273037the CAS Pioneer Hundred Talents Program(Category B)+1 种基金the USTC Research Funds of the Double First-Class Initiativesupported by the China Manned Space Program with grant No.CMS-CSST-2025-A06 and CMS-CSST-2025-A08.
文摘Using a semi-analytic approach,we estimate halo spins for a large sample of H I-rich galaxies from the Arecibo Legacy Fast ALFA Survey and examine the correlation between H I mass fractions and halo spins.Our analysis reveals a strong correlation between halo spin and the H I-to-stellar mass ratio in both low-mass and massive galaxy samples.This finding suggests a universal formation scenario:higher halo spin reduces angular momentum loss and gas condensation,leading to lower star formation rates and weaker feedback,which in turn help retain gas within dark matter halos.
基金financially supporting this research through PPMI KK 2024 Program,contract number 616BO/IT1.C02/KU/2024。
文摘This study examines the properties of standard cold dark matter(CDM),fuzzy dark matter(FDM),and selfinteracting dark matter(SIDM)haloes by analyzing the rotation curves of selected dwarf galaxies from SPARC and LITTLE THINGS in 3D catalogs.Utilizing the Markov Chain Monte Carlo(MCMC)method for model fitting and Bayesian Information Criterion for model comparison,we find that compared to CDM,both FDM and SIDM haloes generally provide better fits to the observed rotation curves.Our findings reveal that the concentration–mass relation derived from the dark matter-only simulations is not followed by concentrations or masses obtained from the rotation curve data.Our analysis highlights a positive correlation between the core sizes of FDM and SIDM haloes and the effective radius of the galaxy,attributable to gravitational couplings between baryonic and dark matter components.Moreover,our exploration of dark matter fractions at characteristic radii indicates considerable diversity in dark matter distributions across dwarf galaxies.Notably,FDM and SIDM exhibit greater diversity than CDM in this respect.
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 Key R&D Program of China through grant 2020YFC2201400the NSFC Key Program through grants 11733010 and 11333008.
文摘We investigate the small-scale clustering of star-forming galaxies(SFGs) in the local universe, using both observational samples from the final data release of the Sloan Digital Sky Survey and IllustrisTNG300, one of the state-of-the-art hydrodynamic simulations of galaxy formation. We measure the projected two-point crosscorrelation function, wp(rp), for subsamples of SFGs with different specific star formation rates(sSFRs) and stellar masses(M*), with respect to reference samples of galaxies with early-type or late-type morphology. On scales smaller than ~100 kpc and at fixed M*, SFGs with higher sSFR are more strongly clustered, reflecting the interaction-induced central star formation found in previous studies. More importantly, the small-scale clusteringsSFR correlation is stronger when the reference sample is limited to late-type galaxies only. This confirms the previous finding that the enhancement of star formation in close pairs depends on the morphology of companion galaxies. These observational trends are broadly reproduced by IllustrisTNG300, indicating that current hydrodynamic simulations are capable of capturing the main recipes governing star formation in interacting/merging galaxies, although further work is needed to identify the exact physical processes involved.
基金supports from the CAS Pioneer Hundred Talents Program(Category B)the National Natural Science Foundation of China(NSFC,grant No.12273037)the USTC Research Funds of the Double First-Class Initiative。
文摘Leveraging the semi-analytic method,we compute halo spins for a substantial sample of H I-bearing galaxies observed in the Arecibo Legacy Fast ALFA Survey.Our statistical analysis reveals a correlation between halo spin and environment,although the trend is subtle.On average,galaxies exhibit a decreasing halo spin tendency in denser environments.This observation contrasts with previous results from N-body simulations in the Lambda Cold Dark Matter framework.The discrepancy may be attributed to environmental gas stripping,leading to an underestimation of halo spins in galaxies in denser environments,or to baryonic processes that significantly alter the original dark matter halo spins,deviating from previous N-body simulation findings.
基金supported by the National Natural Science Foundation of China(NSFC)No.11873055 and No.11933003sponsored(in part)by the Chinese Academy of Sciences(CAS)through a grant to the CAS South America Center for Astronomy(CASSACA)+4 种基金support from project PID2020-114414GB-100,financed by MCIN/AEI/10.13039/501100011033the Junta de Andaluciaía(Spain)grant FQM108support by the National Key R&D Program of China No.2017YFA0402600the National Natural Science Foundation of China(NSFC)grant Nos.11890692,12133008,and 12221003China Manned Space Project No.CMS-CSST2021-A04。
文摘We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic index n<2) in a loca close major-merger galaxy pair sample (H-KPAIR).With data from new aperture photometries in the optical and near-infrared bands (aperture size of 7 kpc) and from the literature,we find that the mean Age of central stellar populations in Spirals with pseudobulges is consistent with that of disky galaxies and is nearly constant against the bulge-to-total ratio (B/T).Paired Spirals have a slightly lower fraction of pure disk galaxies (B/T≤0.1) than their counterparts in the control sample.Compared to SFGs with classical bulges,those with pseudobulges have a higher (>2σ) mean of specific star formation rate (sSFR) enhancement (sSFR_(enh)=0.33±0.07 versus sSFR_(enh)=0.12±0.06) and broader scatter (by~1 dex).The eight SFGs that have the highest sSFR_(enh)in the sample all have pseudobulges.A majority (69%) of paired SFGs with strong enhancement (having sSFR more than5 times the median of the control galaxies) have pseudobulges.The Spitzer data show that the pseudobulges in these galaxies are tightly linked to nuclear/circum-nuclear starbursts.Pseudobulge SFGs in S+S and in S+E pairs have significantly (>3σ) different sSFR enhancement,with the means of sSFR_(enh)=0.45±0.08 and-0.04±0.11respectively.We find a decrease in the sSFR enhancements with the density of the environment for SFGs with pseudobulges.Since a high fraction (5/11) of pseudobulge SFGs in S+E pairs are in rich groups/clusters (loca density N_(1Mpc)≥7),the dense environment might be the cause for their low s SFR_(enh).
基金support from the National Key R&D Program of China(2022YFF0503401)the China Manned Space Project with No.CMS-CSST-2021-A05the National Natural Science Foundation of China(12225301)。
文摘Slitless spectroscopy onboard space telescopes is a powerful tool to detect emission-line objects such as emissionline galaxies(ELGs)and quasars.In this work,we present a study of ELGs observed with slitless spectroscopy by the Hubble Space Telescope(HST)in a deep field of~44 arcmin^(2).This is one of the deepest HST fields with a wealth of imaging and spectral data.In particular,previous VLT/MUSE observations have covered this field and identified a large number of ELGs.We reduce the HST spectra using the latest pipeline with a forward modeling algorithm and construct a sample of ELGs.By comparing with the MUSE spectra,we characterize our ELG detection in the HST spectra,including the impact of the line flux,line width,signal-to-noise ratio,etc.We find that the morphological broadening may affect the detection of ELGs,such that more compact sources are easier to be detected in slitless spectra.We discuss its implications to future slitless spectroscopic surveys that will be carried out by the China Space Station Telescope(CSST)and find that the CSST slitless spectroscopy has a capability comparable to that of HST in terms of the detection of emission lines.
基金supported by the National Natural Science Foundation of China(NSFC,grant No.12173079)。
文摘This paper presents a statistical study of the division of the[CⅡ]158μm line into ionized and neutral components,using a new carbon-to-nitrogen abundance ratio,log(C/N)=0.75,for a sample of 108 local galaxies.We investigate the correlation between the ionized-to-total[CⅡ]ratio([CⅡ]_(ionized)/[CⅡ]_(total))and the farinfrared color f60/f100,finding a moderate negative correlation.Additionally,we explore the dependence of[CⅡ]_(ionized)/[CⅡ]_(total)on various physical properties.We find that[CⅡ]_(ionized)/[CⅡ]_(total)exhibits a weak negative correlation with the offset from the main sequence and a moderate negative correlation with the[OⅢ]88μm/[NⅡ]122μm.Furthermore,no significant correlation with molecular gas mass is found.It shows a positive correlation with metallicity.Our results suggest that[CⅡ]_(ionized)/[CⅡ]_(total)is influenced by the ionization parameter,star formation efficiency and metallicity.
基金sponsored by the National Key R&D Program of China(MOST)with grant No.2022YFA1605300the National Natural Science Foundation of China(NSFC,grant Nos.12273051 and 11933003)Support for this work is also partly provided by the Chinese Academy of Sciences(CAS)through a grant to the South America Center for Astronomy(CASSACA)。
文摘We present the morphological study of 18,572 massive quiescent galaxies at z~1.2, selected by i-y colors in the Hyper Suprime-Cam(HSC) Deep and UltraDeep fields. The majority of our sample(94.3%) fall in the quiescent region in the rest-frame UVJ diagram. Comparing the five HSC bands and the subsample with HST F160W images, consistent with the decreasing effective radius re, Sérsic index n shows an increasing trend indicating a more bulge-dominant morphology towards the infrared. Even for our massive, quiescent galaxies,which are dominated by typical elliptical galaxies with bulges, the reand n values still vary with the wavelengths.For instance, there is a systematic drop in n of ~0.4 going from y band to F160W, making 20% of the HSC “disklike” galaxies appear “bulge-like” in the HST images. We suggest to use caution when comparing galaxy morphological types based on images at different resolutions or at different wavelengths, and whenever possible,to apply a reor n correction. More massive quiescent galaxies are systematically larger than the less massive ones,though no mass dependence is found for n measurements. The size–mass relation based on our sample and lowerz control samples show a monotonic increase of rewith M*, with a power-law of 0.61 ± 0.01, lower than previously found in similar samples of smaller sizes. Future high-resolution space-based surveys like NGRST will help confirm the possible n evolution, and if the flattening at the low-mass end is a genuine physical trend or limited by the image resolutions.
基金support of the China National Key Program for Science and Technology Research and Development of China(2022YFA1602901)the National Natural Science Foundation of China(NSFC,Grant Nos.11988101 and 11873051)+3 种基金the CAS Project for Young Scientists in Basic Research grant(No.YSBR-062)the K.C.Wong Education Foundationthe science research grants from the China Manned Space Projectsupport from the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
文摘With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,specifically AndromedaⅡ,NGC 205,and NGC 185.Initially,three drift scans were executed for these satellites,with a detection limit of 4×10^(18)cm^(-2)(approximately 1.88×10^(3)M_Θof HⅠmass),followed by a more in-depth scan of a specific region.We discovered a C-shaped HⅠarc structure sharing a position and line-of-sight velocity similar to a stellar ring structure around AndromedaⅡ,hinting at a potential connection with AndromedaⅡ.In the context of NGC 205,we identified two mass concentrations in the northeast direction,which could be indicative of tidal streams resulting from the interaction between this galaxy and M31.These new lumps discovered could be very helpful in solving the missing interstellar medium problem for NGC 205.Observations regarding NGC 185are consistent with previous studies,and we did not detect any additional HⅠmaterial around this galaxy.These observational results enhance our understanding of the evolution of these satellite galaxies and provide insight into their historical interactions with the galaxy M31.
基金partially supported by the National SKA Program of China(grant No.2022SKA0120103)the National Natural Science Foundation of China(Nos.11988101 and 11833009,12073036)+2 种基金support from the science research grants from the China Manned Space Project(CMS-CSST-2021-A01,CMS-CSST-2021-B01)the financial support from the National Key R&D Program of China(No.2021YFA1600401 and 2021YFA1600400)the International Partnership Program of Chinese Academy of Sciences,grant No.114A11KYSB20170044。
文摘The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(La GRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known La GRLs,we confirm the correlation between radio power P_(1.4GHz)and stellar mass M_(*)of host galaxies.Most(25/35)La GRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P_(1.4GHz)-M_(*)relation,and the galaxy color,indicating that bluer galaxies at a fixed M_(*)tend to host more powerful radio lobes.Furthermore,the majority(31/36)of La GRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.
基金supported by the National Key Research Development Program of China(grant Nos.2022YFA1602902 and 2022YFA1602903)。
文摘Superthin galaxies are observed to have stellar disks with extremely small minor-to-major axis ratios.In this work,we investigate the formation of superthin galaxies in the TNG100 simulation.We trace the merger history and investigate the evolution of galaxy properties of a selected sample of superthin galaxies and a control sample of galaxies that share the same joint probability distribution in the stellar-mass and color diagram.Through making comparisons between the two galaxy samples,we find that present-day superthin galaxies had similar morphologies as the control sample counterparts at higher redshifts,but have developed extended flat“superthin”morphologies since z~1.During this latter evolution stage,superthin galaxies undergo an overwhelmingly higher frequency of prograde mergers(with orbit-spin angleθ_(orb)≤40°).Accordingly the spins of their dark matter halos have grown significantly and become noticeably higher than those of their normal disk counterparts.This further results in the buildup of their stellar disks at larger distances much beyond the regimes of normal disk galaxies.We also discuss the formation scenario of those superthin galaxies that live in larger dark matter halos as satellite galaxies therein.
基金support from the National Natural Science Foundation of China (grant Nos. 12025303, 11890693,11421303 and 12003031)the CAS Frontier Science Key Research Program (QYZDJ-SSW-SLH006)+2 种基金the K.C. Wong Education Foundationthe science research grants from the China Manned Space Project with No. CMS-CSST-2021-A06support from the Chinese Academy of Sciences President’s International Fellowship Initiative (grant No. 2019PM0020)。
文摘The coevolution between supermassive black holes(SMBHs) and their host galaxies has been proposed for more than a decade,albeit with little direct evidence about black hole accretion activities regulating galaxy star formation at z> 1.In this paper,we study the lifetimes of X-ray active galactic nuclei(AGNs) in UV-selected red sequence(RS),blue cloud(BC) and green valley(GV) galaxies,finding that AGN accretion activities are most prominent in GV galaxies at z ~1.5-2,compared with RS and BC galaxies.We also compare AGN accretion timescales with typical color transition timescales of UV-selected galaxies.We find that the lifetime of GV galaxies at z~1.5-2 is very close to the typical timescale when the AGNs residing in them stay in the high-accretion-rate mode at these redshifts;for BC galaxies,the consistency between the color transition timescale and the black hole strong accretion lifetime is more likely to happen at lower redshifts(z <1).Our results support the scenario where AGN accretion activities govern UV color transitions of host galaxies,making galaxies and their central SMBHs coevolve with each other.
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 Startup Research Fund of the Henan Academy of Sciences under grant No.241841219。
文摘In this paper,we study the rotation curves of the Milky Way galaxy and Andromeda galaxy(M31)by considering their bulge,disk,and halo components.We model the bulge region by the widely accepted de Vaucouleur’s law and the disk region by the well established exponential profile.In order to understand the distribution of dark matter in the halo region,we consider three different dark matter profiles in the framework of the standardΛCDM model namely,Navarro-Frenk-White(NFW),Hernquist and Einasto profiles.We use recent data sets of rotation curves of the Milky Way and Andromeda galaxy.The data consist of rotation velocities of the stars and gas in the galaxy as a function of the radial distance from the center.Using Bayesian statistics,we perform an overall fit including all the components,i.e.,bulge,disk and halo with the data.Our results indicate that the NFW and Hernquist profiles are in concordance with the observational data points.However,the Einasto profile poorly explains the behavior of dark matter in both the galaxies.
基金supported by the Joint Research Fund in AstronomyNational Natural Science Foundation of China(NSFC,grant No.U1931134)+1 种基金the Natural Science Foundation of Hebei,A2020202001the Natural Science Foundation of Tianjin Municipality,22JCYBJC00410。
文摘This study introduces a novel convolutional neural network,the WISE Galaxy Classification Network(WGC),for classifying spiral and elliptical galaxies using Wide-field Infrared Survey Explorer(WISE)images.WGC attains an accuracy of 89.03%,surpassing the combined use of K-means or SVM with the Color-Color method in more accurately identifying galaxy morphologies.The enhanced variant,WGC_mag,integrates magnitude parameters with image features,further boosting the accuracy to 89.89%.The research also delves into the criteria for galaxy classification,discovering that WGC primarily categorizes dust-rich images as elliptical galaxies,corresponding to their lower star formation rates,and classifies less dusty images as spiral galaxies.The paper explores the consistency and complementarity of WISE infrared images with SDSS optical images in galaxy morphology classification.The SDSS Galaxy Classification Network(SGC),trained on SDSS images,achieved an accuracy of 94.64%.The accuracy reached 99.30% when predictions from SGC and WGC were consistent.Leveraging the complementarity of features in WISE and SDSS images,a novel variant of a classifier,namely the Multi-band Galaxy Morphology Integrated Classifier,has been developed.This classifier elevates the overall prediction accuracy to 95.39%.Lastly,the versatility of WGC was validated in other data sets.On the HyperLEDA data set,the distinction between elliptical galaxies and Sc,Scd and Sd spiral galaxies was most pronounced,achieving an accuracy of 90%,surpassing the classification results of the Galaxy Zoo 2 labeled WISE data set.This research not only demonstrates the effectiveness of WISE images in galaxy morphology classification but also represents an attempt to integrate multi-band astronomical data to enhance understanding of galaxy structures and evolution.
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 from“BASIS”Foundation for the Development of Theoretical Physics and Mathematics(grant No.23-2-2-6-1)。
文摘A corotation radius is a key characteristic of disk galaxies that is essential to determine the angular speed of the spiral structureΩ_p,and therefore understand its nature.In the literature,there are plenty of methods to estimate this value,but do these measurements have any consistency?In this work,we collected a data set of corotation radius measurements for 547 galaxies,300 of which had at least two values.An initial analysis reveals that most objects have rather inconsistent corotation radius positions.Moreover,a significant fraction of galactic disks is distinguished by a large error coverage and almost uniform distribution of measurements.These findings do not have any relation to spiral type,Hubble classification,or presence of a bar.Among other reasons,obtained results could be explained by the transient nature of spirals in a considerable part of galaxies.We have made our collected data sample publicly available,and have demonstrated on one example how it could be useful for future research by investigating a winding time value for a sample of galaxies with possible multiple spiral arm patterns.
基金supported by the China Manned Space Project with No.CMSCSST-2021-A06the National Key R&D Program of China with No.2021YFA1600404+7 种基金the National Natural Science Foundation of China(NSFCgrant Nos.12173079 and 11991051)The STARLIGHT project is supported by the Brazilian agencies CNPqCAPESand FAPESP and by the France-Brazil CAPES/Cofecub programFunding for SDSS-III has been provided by the Alfred P.Sloan Foundationthe National Science Foundationthe U.S.Department of Energy Office of Science。
文摘In this paper we investigate the stellar populations and star formation histories of 235 active galactic nucleus(AGN)-host dwarf galaxies,consisting of four samples identified separately with different methods(i.e.,radio,X-ray,mid-IR and variability),utilizing the synthesis code STARLIGHT and spectra from the Sloan Digital Sky Survey Data Release 8.Our results show that the variability sample is the oldest,while the mid-IR sample is the youngest,for which the luminosity at 4020?is dominated(>50%)by the young population(t<10~8yr).The light-weighted mean stellar age of the whole sample is in general about 0.7 dex younger than the optical sample studied in Cai et al.We compare the population results between fitting models with and without a power-law(PL)component and find that the neglect of a PL component would lead to an under-and over-estimation by 0.2 and0.1 dex for the light-and mass-weighted mean stellar age,respectively,for our sample of dwarf galaxies,which has a mean fractional contribution of~16%from the AGN.In addition,we obtain further evidence for a possible suppression of star formation in the host galaxy by the central AGN.We also find that there exists an anticorrelation between the extinction-corrected[O III]luminosity and light-weighted mean stellar age,confirming our previous finding that there is a physical connection between AGN and star-forming activities in AGN-host dwarfs.
基金supported by the National SKA Program of China(grant No.2020SKA0110100)the CAS Project for Young Scientists in Basic Research (No.YSBR-092)the science research grants from the China Manned Space Project with Nos.CMS-CSST-2021-A02 and GHfund C(202407031909)
文摘Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming interstellar medium(ISM)has relied on heuristic sub-grid models.However,recent high-resolution simulations of the ISM that directly resolve the regulation of star formation suggest different mean relations for the dependences of pressure and star formation rate on the average gas density.In this study,we adopt such a modern,physically grounded parameterization inspired by the TIGRESS small-scale simulations.We dub this model TEQS and use it for a detailed comparative analysis of the formation and evolution of a Milky Way-sized galaxy when compared with the widely used TNG model.By employing high-resolution simulations in tall box setups,we first investigate the structural differences expected for these two models when applied to different self-gravitating gas surface densities.Our results indicate that TEQS produces considerably thinner gaseous layers and can be expected to form stellar distributions with smaller scale-height than TNG,especially at higher surface density.To test whether this induces systematic structural differences in cosmological galaxy formation simulations,we carry out zoom-in simulations of 12 galaxies taken from the set of Milky Way-sized galaxies that have been studied in the Auriga project.Comparing results for these galaxies shows that disk galaxies formed with the TEQS model have on average very similar stellar mass but are more concentrated in their central regions and exhibit smaller stellar radii compared to those formed with the TNG model.The differences in the scale-heights of the formed stellar disks are only marginal,however,suggesting that other factors for setting the thickness of the disk are more important than the applied ISM equation-of-state model.Overall,the predicted galaxy structure is quite similar for TNG and TEQS despite significant differences in the employed star formation law,demonstrating that feedback processes are more important in regulating the stellar mass than the precise star formation law itself.
