This paper modifies the Farnes’ unifying theory of dark energy and dark matter which are negative-mass, created continuously from the negative-mass universe in the positive-negative mass universe pair. The first modi...This paper modifies the Farnes’ unifying theory of dark energy and dark matter which are negative-mass, created continuously from the negative-mass universe in the positive-negative mass universe pair. The first modification explains that observed dark energy is 68.6%, greater than 50% for the symmetrical positive-negative mass universe pair. This paper starts with the proposed positive-negative-mass 11D universe pair (without kinetic energy) which is transformed into the positive-negative mass 10D universe pair and the external dual gravities as in the Randall-Sundrum model, resulting in the four equal and separate universes consisting of the positive-mass 10D universe, the positive-mass massive external gravity, the negative-mass 10D universe and the negative-mass massive external gravity. The positive-mass 10D universe is transformed into 4D universe (home universe) with kinetic energy through the inflation and the Big Bang to create positive-mass dark matter which is five times of positive-mass baryonic matter. The other three universes without kinetic energy oscillate between 10D and 10D through 4D, resulting in the hidden universes when D > 4 and dark energy when D = 4, which is created continuously to our 4D home universe with the maximum dark energy = 3/4 = 75%. In the second modification to explain dark matter in the CMB, dark matter initially is not repulsive. The condensed baryonic gas at the critical surface density induces dark matter repulsive force to transform dark matter in the region into repulsive dark matter repulsing one another. The calculated percentages of dark energy, dark matter, and baryonic matter are 68.6 (as an input from the observation), 26 and 5.2, respectively, in agreement with observed 68.6, 26.5 and 4.9, respectively, and dark energy started in 4.33 billion years ago in agreement with the observed 4.71 <span style="white-space:nowrap;">±</span> 0.98 billion years ago. In conclusion, the modified Farnes’ unifying theory reinterprets the Farnes’ equations, and is a unifying theory of dark energy, dark matter, and baryonic matter in the positive-negative mass universe pair. The unifying theory explains protogalaxy and galaxy evolutions in agreement with the observations.展开更多
We use a semi-analytic galaxy formation model to study the co-evolution of supermassive black holes(SMBHs) with their host galaxies.Although the coalescence of SMBHs is not important,the quasarmode accretion induced b...We use a semi-analytic galaxy formation model to study the co-evolution of supermassive black holes(SMBHs) with their host galaxies.Although the coalescence of SMBHs is not important,the quasarmode accretion induced by mergers plays a dominant role in the growth of SMBHs.Mergers play a more important role in the growth of SMBH host galaxies than in the SMBH growth.It is the combined contribution from quasar mode accretion and mergers to the SMBH growth and the combined contribution from starburst and mergers to their host galaxy growth that determine the observed scaling relation between the SMBH masses and their host galaxy masses.We also find that mergers are more important in the growth of SMBH host galaxies compared to normal galaxies which share the same stellar mass range as the SMBH host galaxies.展开更多
I present the results oféchelle spectroscopy of a bright H II region in the irregular galaxy IC 4662 and their comparison with results from long-slit spectroscopy of the same region.All observations were obtained...I present the results oféchelle spectroscopy of a bright H II region in the irregular galaxy IC 4662 and their comparison with results from long-slit spectroscopy of the same region.All observations were obtained with the standard spectrographs of the Southern African Large Telescope:(1)low and medium spectral resolution spectrograph Robert Stobie Spectrograph(R≈800)and(2)échelle spectrograph HRS(R=16,000–1,7000).In both types of data the intensities of most of the emission lines were measured and abundances of oxygen and N Ne,S,Ar,Cl and Fe were determined as well as physical parameters of the H II region.The chemical abundances were obtained from both types of data with the Te-method.Abundances calculated from both types of data agree to within the cited uncertainties.The analysis of theéchelle data revealed three distinct kinematic subsystems within the studied H II region:a narrow component(NC,σ≈12 km s^(-1)),a broad component(BC,σ≈40 km s^(-1)),and a very broad component(VBC,σ≈60–110 km s^(-1),detected only in the brightest emission lines).The elementa abundances for the NC and BC subsystems were determined using the Te-method.The velocity dispersion dependence on the ionization potential of elements showed no correlation for the NC,indicating a well-mixed turbulent medium,while the BC exhibited pronounced stratification,characteristic of an expanding shell.Based on a detailed analysis of the kinematics and chemical composition,it was concluded that the BC is associated with the region surrounding a Wolf-Rayet(WR)star of spectral type WN7-8.The stellar wind from this WR star interacts with a shell ejected during an earlier evolutionary stage(either as a red supergiant or a luminous blue variable LBV),which is enriched in nitrogen.These findings highlight the importance of high spectral resolution for detecting small-scale(25 pc)chemical inhomogeneities and for understanding the feedback mechanisms of massive stars in low-metallicity environments.展开更多
We have investigated the role that different galaxy types have in galaxy-galaxy interactions in compact groups. N-body simulations of 6 galaxies consisting of a differing mixture of galaxy types were run to compare th...We have investigated the role that different galaxy types have in galaxy-galaxy interactions in compact groups. N-body simulations of 6 galaxies consisting of a differing mixture of galaxy types were run to compare the relative importance of galaxy population demographic on evolution. Three different groups with differing galaxy content were tested: all spiral, a single elliptical and 50% elliptical. Tidal interaction strength and duration were recorded to assess the importance of an interaction. A group with an equal number of spiral and elliptical galaxies has some of the longest and strongest interactions with elliptical-elliptical interactions being most significant. These elliptical-elliptical interactions are not dominated by a single large event but consist of multiple interactions. Elliptical galaxies tidally interacting with spiral galaxies, have the next strongest interaction events. For the case when a group only has a single elliptical, the largest magnitude tidal interaction is an elliptical on a spiral. Spirals interact with each other through many small interactions. For a spiral only group, the interactions are the weakest compared to the other group types. These spiral interactions are not dominated by any singular event that might be expected to lead to a merger but are more of an ongoing harassment. These results suggest that within a compact group, early type galaxies will not form via merger out of an assemblage of spiral galaxies but rather that compact groups, in effect form around an early type galaxy.展开更多
Based on the undisturbed, finite thickness disk gravitational potential, we carried out 3-D Monte Carlo simulations of normal pulsars. We find that their scale height evolves in a similar way for different velocity di...Based on the undisturbed, finite thickness disk gravitational potential, we carried out 3-D Monte Carlo simulations of normal pulsars. We find that their scale height evolves in a similar way for different velocity dispersions （δv）： it first increases linearly with time, reaches a peak, then gradually decreases, and finally approaches a stable asymptotic value. The initial velocity dispersion has a very large influence on the scale height. The time evolution of the scale height is studied. When the magnetic decay age is used as the time variable, the observed scale height has a similar trend as the simulated results in the linear stage, from which we derive velocity dispersions in the range 70 - 178km s^-1, which are near the statistical result of 90 - 270km s^-1 for 92 pulsars with known transverse velocities. If the characteristic age is used as the time variable, then the observed and theoretical curves roughly agree for t 〉 10^8 yr only if av 〈 25km s^-1.展开更多
In Part 1 of this work, we showed that our new model of cosmology can account for the origin of all cosmic structures ranging in size from stars up to superclusters. In this model, at the time of nucleosynthesis, an i...In Part 1 of this work, we showed that our new model of cosmology can account for the origin of all cosmic structures ranging in size from stars up to superclusters. In this model, at the time of nucleosynthesis, an imprint embedded in the vacuum regulated the creation of the protons (and electrons) that later made up the structures. Immediately after nucleosynthesis and for a considerable period afterward, the evolution was completely determined by the expansion of the universe. Gradually, however, gravitational influences became more important until finally, the expansion of the structures-to-be ceased at their zero velocity points. Stars, galaxies, and galaxy clusters all reached their zero velocity points more or less simultaneously at the usually accepted time of the beginning of galaxy formation. From that point onward, the evolution gravitation came to dominate the evolution although the expansion still exerted its influence. In this paper, we examine the subsequent cluster evolution in some detail. We establish the conditions required to prevent a free-fall collapse of the clusters and then show that galaxies with quasar-like active nuclei located within the cluster were the sources of the necessary radiation. We also show that the required galactic supermassive black holes were a consequence of the initial free-fall collapse of all galaxies.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
We present a stellar population synthesis study of a type II luminous infrared galaxy, IRAS F21013-0739. Optical images show clear characteristics of a merger remnant. The H-band absolute magnitude is MH = -25.1, whic...We present a stellar population synthesis study of a type II luminous infrared galaxy, IRAS F21013-0739. Optical images show clear characteristics of a merger remnant. The H-band absolute magnitude is MH = -25.1, which is -2 times as luminous as L＊ galaxies. Stellar populations are obtained through the stellar synthesis code STARLIGHT. We find that it experienced a recent starburst （SB） phase - 100 Myr ago. By reconstructing the ultraviolet-to-optical spectrum, and adopting Calzetti et al. and Leitherer et al.＇s extinction curves, we estimate the past infrared （IR） luminosities of the host galaxy and find it may have experienced an ultraluminous infrared galaxy phase which lasted for about 100 Myr. Its i-band absolute magnitude is Mi = -22.463, and its spectral type shows type 2 active galactic nucleus （AGN） characteristics. The mass of the supermassive black-hole is estimated to be MBH = 1.6 × 107 M⊙ （lower- limit）. The Eddington ratio Lbol/LEdd is 0.15, which is typical of Palomar-Green （PG） quasars. Both the nuclear SB and AGN contribute to the present IR luminosity budget, and the SB contributes -67%. On the diagram of IR color versus IR/opfical excess, it is located between IR quasars and PG quasars. These results indicate that IRAS F21013-0739 has probably evolved from a ULIRG, and it can possibly evolve into an AGN.展开更多
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
To address the disk-halo degeneracy problem,we investigate the nearby barred spiral galaxy NGC 1097.We construct mass models using 3.6 and 4.5μm near-infrared photometric images from the S^(4)G survey,constrained by ...To address the disk-halo degeneracy problem,we investigate the nearby barred spiral galaxy NGC 1097.We construct mass models using 3.6 and 4.5μm near-infrared photometric images from the S^(4)G survey,constrained by rotation curves derived from CO(J=2–1)data from the PHANGS-ALMA survey.These models serve as inputs for a suite of hydrodynamic simulations,where we systematically test the influence of key parameters including the disk mass scaling factor(f_(M)),bar pattern speed(Ω_(b)),and gas sound speed(c_(s)).By comparing the CO(2–1)kinematic maps in the bar region with those from the simulations,we perform a standardχ^(2)analysis to identify the best-fit model.The best-fit model reproduces the observed morphological and kinematic gas features of the galaxy,indicating that NGC 1097 likely hosts a maximal disk with a slowly rotating bar.We also test the influence of a boxy/peanut-shaped(B/P)bulge by incorporating a double-peaked vertical density profile into the model.This B/P structure tends to weaken the bar’s non-axisymmetric potential and necessitate a higher bar pattern speed to reproduce the observed gas morphology.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
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
The role of galaxy morphology and stellar population properties in galaxy evolution is crucial for understanding the transition from star-forming to quiescent galaxies.We present an analysis of 94 galaxies with Hδabs...The role of galaxy morphology and stellar population properties in galaxy evolution is crucial for understanding the transition from star-forming to quiescent galaxies.We present an analysis of 94 galaxies with Hδabsorption line equivalent widths greater than 2?,selected from the DEEP2 survey EGS field(0<z<1).The wealth of multi-wavelength coverage enables accurate stellar mass measurements from SED fitting,SFR measurements from UV and MIR,and galaxy population classification based on the UVJ diagram.Using HST F814W images,we performed a morphological analysis and found that most galaxies exhibit disk-like structures,with some showing bulge-dominated profiles.The size of our sample is roughly in between the star-forming and quiescent galaxies,implying a transition of galaxy population.We also examined the role of central stellar density(Σ1)in galaxy evolution and found that galaxies with higherΣ1tend to evolve into quiescent galaxies earlier,supporting the“downsizing”scenario.These findings underscore the importance of size,mass,and central density in galaxy evolution.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 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
The integrated HI emission from hierarchical structures such as groups and clusters of galax- ies can be detected by FAST at intermediate redshifts. Here we propose to use FAST to study the evolution of the global HI ...The integrated HI emission from hierarchical structures such as groups and clusters of galax- ies can be detected by FAST at intermediate redshifts. Here we propose to use FAST to study the evolution of the global HI content of clusters and groups over cosmic time by measuring their integrated HI emissions. We use the Virgo Cluster as an example to estimate the detection limit of FAST, and have estimated the integration time to detect a Virgo type cluster at different redshifts （from z = 0.1 to z ---- 1.5）. We have also employed a semi-analytic model （SAM） to simulate the evolution of HI contents in galaxy clusters. Our simulations suggest that the HI mass of a Virgo-like cluster could be 2-3 times higher and the physical size could be more than 50% smaller when redshift increases from z = 0.3 to z = 1. Thus the integration time could be reduced significantly and gas rich clusters at intermediate redshifts can be detected by FAST in less than 2 hours of integration time. For the local Universe, we have also used SAM simulations to create mock catalogs of clusters to predict the outcomes from FAST all sky surveys. Comparing with the optically selected catalogs derived by cross matching the galaxy catalogs from the SDSS survey and the ALFALFA survey, we find that the HI mass distribution of the mock catalog with 20 s of integration time agrees well with that of observations. However, the mock catalog with 120 s of integration time predicts many more groups and clusters that contain a population of low mass HI galaxies not detected by the ALFALFA survey. A future deep HI blind sky survey with FAST would be able to test such prediction and set constraints on the numerical simulation models. The observational strategy and sample selections for future FAST observations of galaxy clusters at high redshifts are also discussed.展开更多
Based on a sample of 79 local advanced merger （adv-merger） （U）LIRGs, we search for evidence of quenching processes by investigating the distributions of star formation history indicators （EW（Ha）, EW（HfiA） and...Based on a sample of 79 local advanced merger （adv-merger） （U）LIRGs, we search for evidence of quenching processes by investigating the distributions of star formation history indicators （EW（Ha）, EW（HfiA） and D,（4000）） on the NUV-r color-mass and SFR-M, diagrams. The distributions of EW（Ha） and Dn（4000） on the NUV-r color-mass diagram show clear trends that at a given stellar mass, galaxies with redder NUV-r colors have smaller EW（Ha） and larger Dn （4000）. The reddest adv-merger （U）LIRGs close to the green valley mostly have Dn（4000）〉 1.4. In addition, in the SFR-M, diagram, as the SFR decreases, the EW（Ha） decreases and the Dn （4000） increases, implying that the adv-merger （U）LIRGs on the star formation main sequence have more evolved stellar populations than those above the main sequence. These results indicate that a fraction of the adv-merger （U）LIRGs have already exhibited signs of fading from the starburst phase and that the NUV-r reddest adv-merger （U）LIRGs are likely at the initial stage of post-starbursts with an age of - 1 Gyr, which is consistent with the gas exhaustion time-scales. Therefore, our results offer additional support for the fast evolutionary track from the blue cloud to the red sequence.展开更多
We investigate two classes of conditions for galaxy quenching at 0.510^10 M⊙)have much higher stellar mass surface densities within the central 1 kpc(∑1)and smaller sizes than star-forming galaxies in the same stell...We investigate two classes of conditions for galaxy quenching at 0.510^10 M⊙)have much higher stellar mass surface densities within the central 1 kpc(∑1)and smaller sizes than star-forming galaxies in the same stellar mass range.In addition,the quiescent fractions significantly increase with the increase of∑1 regardless of whether galaxies are centrals or satellites.In contrast,we find that the overall lower-mass quiescent galaxies(M*<~10^10M⊙)have slightly higher E1 and comparable sizes compared to starforming galaxies of the same mass and at the same redshift.At z<1.5,satellites have higher halo masses and larger quiescent fractions than those of centrals at a given∑1(stellar mass).Our findings indicate that the significant growth of the galaxy cores is closely related to the quenching of massive galaxies since z^2.5,while the environmental effect plays an important role in the quenching of low-mass galaxies at z≤1.5.展开更多
We compile a new sample of 89 open clusters with ages, distances and metallicities available. We derive a radial iron gradient of about -0.099±0.008 dex kpc^(-1) (unweighted) for the whole sample, which is somewh...We compile a new sample of 89 open clusters with ages, distances and metallicities available. We derive a radial iron gradient of about -0.099±0.008 dex kpc^(-1) (unweighted) for the whole sample, which is somewhat greater than the most recent determination of oxygen gradient from nebulae and young stars. By dividing the clusters into age groups, we show that the iron gradient was steeper in the past and has evolved slowly in time. Current data show a substantial scatter of the cluster metallicities indicating that the Galactic disk has undergone a very rapid, inhomogeneous enrichment. Also, based on a simple, but quite successful model of chemical evolution of the Milky Way disk, we make a detailed calculation of the iron abundance gradient and its time evolution. The predicted current iron gradient is about -0.072 dex kpc^(-1). The model also predicts a steady flattening of the iron gradient with time, which agrees with the result from our open cluster sample.展开更多
Understanding galaxy formation is one of the most pressing issues in cos- mology. We review the current status of galaxy formation from both an observational and a theoretical perspective, and summarize the prospects ...Understanding galaxy formation is one of the most pressing issues in cos- mology. We review the current status of galaxy formation from both an observational and a theoretical perspective, and summarize the prospects for future advances.展开更多
文摘This paper modifies the Farnes’ unifying theory of dark energy and dark matter which are negative-mass, created continuously from the negative-mass universe in the positive-negative mass universe pair. The first modification explains that observed dark energy is 68.6%, greater than 50% for the symmetrical positive-negative mass universe pair. This paper starts with the proposed positive-negative-mass 11D universe pair (without kinetic energy) which is transformed into the positive-negative mass 10D universe pair and the external dual gravities as in the Randall-Sundrum model, resulting in the four equal and separate universes consisting of the positive-mass 10D universe, the positive-mass massive external gravity, the negative-mass 10D universe and the negative-mass massive external gravity. The positive-mass 10D universe is transformed into 4D universe (home universe) with kinetic energy through the inflation and the Big Bang to create positive-mass dark matter which is five times of positive-mass baryonic matter. The other three universes without kinetic energy oscillate between 10D and 10D through 4D, resulting in the hidden universes when D > 4 and dark energy when D = 4, which is created continuously to our 4D home universe with the maximum dark energy = 3/4 = 75%. In the second modification to explain dark matter in the CMB, dark matter initially is not repulsive. The condensed baryonic gas at the critical surface density induces dark matter repulsive force to transform dark matter in the region into repulsive dark matter repulsing one another. The calculated percentages of dark energy, dark matter, and baryonic matter are 68.6 (as an input from the observation), 26 and 5.2, respectively, in agreement with observed 68.6, 26.5 and 4.9, respectively, and dark energy started in 4.33 billion years ago in agreement with the observed 4.71 <span style="white-space:nowrap;">±</span> 0.98 billion years ago. In conclusion, the modified Farnes’ unifying theory reinterprets the Farnes’ equations, and is a unifying theory of dark energy, dark matter, and baryonic matter in the positive-negative mass universe pair. The unifying theory explains protogalaxy and galaxy evolutions in agreement with the observations.
基金supported by NSFC grants (Nos.11573033,11622325,11425312 and 11988101)supported by NSFC grant (No.11803045)+2 种基金the “Recruitment Program of Global Youth Experts” of China,the NAOC (Grant Y434011V01)supported by the National Key R&D Program of China (No.2017YFB0203300)the Key Program of NFSC (Grant 11733010)。
文摘We use a semi-analytic galaxy formation model to study the co-evolution of supermassive black holes(SMBHs) with their host galaxies.Although the coalescence of SMBHs is not important,the quasarmode accretion induced by mergers plays a dominant role in the growth of SMBHs.Mergers play a more important role in the growth of SMBH host galaxies than in the SMBH growth.It is the combined contribution from quasar mode accretion and mergers to the SMBH growth and the combined contribution from starburst and mergers to their host galaxy growth that determine the observed scaling relation between the SMBH masses and their host galaxy masses.We also find that mergers are more important in the growth of SMBH host galaxies compared to normal galaxies which share the same stellar mass range as the SMBH host galaxies.
基金support from the National Research Foundation(NRF)of South Africa。
文摘I present the results oféchelle spectroscopy of a bright H II region in the irregular galaxy IC 4662 and their comparison with results from long-slit spectroscopy of the same region.All observations were obtained with the standard spectrographs of the Southern African Large Telescope:(1)low and medium spectral resolution spectrograph Robert Stobie Spectrograph(R≈800)and(2)échelle spectrograph HRS(R=16,000–1,7000).In both types of data the intensities of most of the emission lines were measured and abundances of oxygen and N Ne,S,Ar,Cl and Fe were determined as well as physical parameters of the H II region.The chemical abundances were obtained from both types of data with the Te-method.Abundances calculated from both types of data agree to within the cited uncertainties.The analysis of theéchelle data revealed three distinct kinematic subsystems within the studied H II region:a narrow component(NC,σ≈12 km s^(-1)),a broad component(BC,σ≈40 km s^(-1)),and a very broad component(VBC,σ≈60–110 km s^(-1),detected only in the brightest emission lines).The elementa abundances for the NC and BC subsystems were determined using the Te-method.The velocity dispersion dependence on the ionization potential of elements showed no correlation for the NC,indicating a well-mixed turbulent medium,while the BC exhibited pronounced stratification,characteristic of an expanding shell.Based on a detailed analysis of the kinematics and chemical composition,it was concluded that the BC is associated with the region surrounding a Wolf-Rayet(WR)star of spectral type WN7-8.The stellar wind from this WR star interacts with a shell ejected during an earlier evolutionary stage(either as a red supergiant or a luminous blue variable LBV),which is enriched in nitrogen.These findings highlight the importance of high spectral resolution for detecting small-scale(25 pc)chemical inhomogeneities and for understanding the feedback mechanisms of massive stars in low-metallicity environments.
文摘We have investigated the role that different galaxy types have in galaxy-galaxy interactions in compact groups. N-body simulations of 6 galaxies consisting of a differing mixture of galaxy types were run to compare the relative importance of galaxy population demographic on evolution. Three different groups with differing galaxy content were tested: all spiral, a single elliptical and 50% elliptical. Tidal interaction strength and duration were recorded to assess the importance of an interaction. A group with an equal number of spiral and elliptical galaxies has some of the longest and strongest interactions with elliptical-elliptical interactions being most significant. These elliptical-elliptical interactions are not dominated by a single large event but consist of multiple interactions. Elliptical galaxies tidally interacting with spiral galaxies, have the next strongest interaction events. For the case when a group only has a single elliptical, the largest magnitude tidal interaction is an elliptical on a spiral. Spirals interact with each other through many small interactions. For a spiral only group, the interactions are the weakest compared to the other group types. These spiral interactions are not dominated by any singular event that might be expected to lead to a merger but are more of an ongoing harassment. These results suggest that within a compact group, early type galaxies will not form via merger out of an assemblage of spiral galaxies but rather that compact groups, in effect form around an early type galaxy.
基金Supported by the National Natural Science Foundation of China.
文摘Based on the undisturbed, finite thickness disk gravitational potential, we carried out 3-D Monte Carlo simulations of normal pulsars. We find that their scale height evolves in a similar way for different velocity dispersions （δv）： it first increases linearly with time, reaches a peak, then gradually decreases, and finally approaches a stable asymptotic value. The initial velocity dispersion has a very large influence on the scale height. The time evolution of the scale height is studied. When the magnetic decay age is used as the time variable, the observed scale height has a similar trend as the simulated results in the linear stage, from which we derive velocity dispersions in the range 70 - 178km s^-1, which are near the statistical result of 90 - 270km s^-1 for 92 pulsars with known transverse velocities. If the characteristic age is used as the time variable, then the observed and theoretical curves roughly agree for t 〉 10^8 yr only if av 〈 25km s^-1.
文摘In Part 1 of this work, we showed that our new model of cosmology can account for the origin of all cosmic structures ranging in size from stars up to superclusters. In this model, at the time of nucleosynthesis, an imprint embedded in the vacuum regulated the creation of the protons (and electrons) that later made up the structures. Immediately after nucleosynthesis and for a considerable period afterward, the evolution was completely determined by the expansion of the universe. Gradually, however, gravitational influences became more important until finally, the expansion of the structures-to-be ceased at their zero velocity points. Stars, galaxies, and galaxy clusters all reached their zero velocity points more or less simultaneously at the usually accepted time of the beginning of galaxy formation. From that point onward, the evolution gravitation came to dominate the evolution although the expansion still exerted its influence. In this paper, we examine the subsequent cluster evolution in some detail. We establish the conditions required to prevent a free-fall collapse of the clusters and then show that galaxies with quasar-like active nuclei located within the cluster were the sources of the necessary radiation. We also show that the required galactic supermassive black holes were a consequence of the initial free-fall collapse of all galaxies.
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supported by the National Natural Science Foundation of China (Grant Nos. 10833006, 10773014, and 10978014)the Ministry of Science and Technology National Basic Science program (973 Program, Grant No. 2007CB815406)
文摘We present a stellar population synthesis study of a type II luminous infrared galaxy, IRAS F21013-0739. Optical images show clear characteristics of a merger remnant. The H-band absolute magnitude is MH = -25.1, which is -2 times as luminous as L＊ galaxies. Stellar populations are obtained through the stellar synthesis code STARLIGHT. We find that it experienced a recent starburst （SB） phase - 100 Myr ago. By reconstructing the ultraviolet-to-optical spectrum, and adopting Calzetti et al. and Leitherer et al.＇s extinction curves, we estimate the past infrared （IR） luminosities of the host galaxy and find it may have experienced an ultraluminous infrared galaxy phase which lasted for about 100 Myr. Its i-band absolute magnitude is Mi = -22.463, and its spectral type shows type 2 active galactic nucleus （AGN） characteristics. The mass of the supermassive black-hole is estimated to be MBH = 1.6 × 107 M⊙ （lower- limit）. The Eddington ratio Lbol/LEdd is 0.15, which is typical of Palomar-Green （PG） quasars. Both the nuclear SB and AGN contribute to the present IR luminosity budget, and the SB contributes -67%. On the diagram of IR color versus IR/opfical excess, it is located between IR quasars and PG quasars. These results indicate that IRAS F21013-0739 has probably evolved from a ULIRG, and it can possibly evolve into an AGN.
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supported by the National Natural Science Foundation of China under grant Nos.12103032,12025302,11773052 and 11761131016(NSFC-DFG)the“111”Project of the Ministry of Education of China under grant No.B20019+1 种基金the China Manned Space Project under grant No.CMS-CSST-2025-A11support from a Newton Advanced Fellowship awarded by the Royal Society and the Newton Fund。
文摘To address the disk-halo degeneracy problem,we investigate the nearby barred spiral galaxy NGC 1097.We construct mass models using 3.6 and 4.5μm near-infrared photometric images from the S^(4)G survey,constrained by rotation curves derived from CO(J=2–1)data from the PHANGS-ALMA survey.These models serve as inputs for a suite of hydrodynamic simulations,where we systematically test the influence of key parameters including the disk mass scaling factor(f_(M)),bar pattern speed(Ω_(b)),and gas sound speed(c_(s)).By comparing the CO(2–1)kinematic maps in the bar region with those from the simulations,we perform a standardχ^(2)analysis to identify the best-fit model.The best-fit model reproduces the observed morphological and kinematic gas features of the galaxy,indicating that NGC 1097 likely hosts a maximal disk with a slowly rotating bar.We also test the influence of a boxy/peanut-shaped(B/P)bulge by incorporating a double-peaked vertical density profile into the model.This B/P structure tends to weaken the bar’s non-axisymmetric potential and necessitate a higher bar pattern speed to reproduce the observed gas morphology.
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 for grant No.2022YFA1605300the National Natural Science Foundation of China(NSFC,Grant Nos.11933003,12173045,and 12273051)。
文摘The role of galaxy morphology and stellar population properties in galaxy evolution is crucial for understanding the transition from star-forming to quiescent galaxies.We present an analysis of 94 galaxies with Hδabsorption line equivalent widths greater than 2?,selected from the DEEP2 survey EGS field(0<z<1).The wealth of multi-wavelength coverage enables accurate stellar mass measurements from SED fitting,SFR measurements from UV and MIR,and galaxy population classification based on the UVJ diagram.Using HST F814W images,we performed a morphological analysis and found that most galaxies exhibit disk-like structures,with some showing bulge-dominated profiles.The size of our sample is roughly in between the star-forming and quiescent galaxies,implying a transition of galaxy population.We also examined the role of central stellar density(Σ1)in galaxy evolution and found that galaxies with higherΣ1tend to evolve into quiescent galaxies earlier,supporting the“downsizing”scenario.These findings underscore the importance of size,mass,and central density in galaxy evolution.
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 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support by NSFC grant No. U1531246the China Ministry of Science and Technology under the State Key Research Program (2017YFA0402600)+3 种基金Jian Fu acknowledges support by NSFC No. U1531123the Youth Innovation Promotion Association of CASthe Opening Project of the Key Laboratory of Computational Astrophysics, National Astronomical Observatories, CASthe National Science Foundation (AST-1100968)
文摘The integrated HI emission from hierarchical structures such as groups and clusters of galax- ies can be detected by FAST at intermediate redshifts. Here we propose to use FAST to study the evolution of the global HI content of clusters and groups over cosmic time by measuring their integrated HI emissions. We use the Virgo Cluster as an example to estimate the detection limit of FAST, and have estimated the integration time to detect a Virgo type cluster at different redshifts （from z = 0.1 to z ---- 1.5）. We have also employed a semi-analytic model （SAM） to simulate the evolution of HI contents in galaxy clusters. Our simulations suggest that the HI mass of a Virgo-like cluster could be 2-3 times higher and the physical size could be more than 50% smaller when redshift increases from z = 0.3 to z = 1. Thus the integration time could be reduced significantly and gas rich clusters at intermediate redshifts can be detected by FAST in less than 2 hours of integration time. For the local Universe, we have also used SAM simulations to create mock catalogs of clusters to predict the outcomes from FAST all sky surveys. Comparing with the optically selected catalogs derived by cross matching the galaxy catalogs from the SDSS survey and the ALFALFA survey, we find that the HI mass distribution of the mock catalog with 20 s of integration time agrees well with that of observations. However, the mock catalog with 120 s of integration time predicts many more groups and clusters that contain a population of low mass HI galaxies not detected by the ALFALFA survey. A future deep HI blind sky survey with FAST would be able to test such prediction and set constraints on the numerical simulation models. The observational strategy and sample selections for future FAST observations of galaxy clusters at high redshifts are also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos11373027,10973011 and 11003015)sponsored by SRF for ROCS, SEM
文摘Based on a sample of 79 local advanced merger （adv-merger） （U）LIRGs, we search for evidence of quenching processes by investigating the distributions of star formation history indicators （EW（Ha）, EW（HfiA） and D,（4000）） on the NUV-r color-mass and SFR-M, diagrams. The distributions of EW（Ha） and Dn（4000） on the NUV-r color-mass diagram show clear trends that at a given stellar mass, galaxies with redder NUV-r colors have smaller EW（Ha） and larger Dn （4000）. The reddest adv-merger （U）LIRGs close to the green valley mostly have Dn（4000）〉 1.4. In addition, in the SFR-M, diagram, as the SFR decreases, the EW（Ha） decreases and the Dn （4000） increases, implying that the adv-merger （U）LIRGs on the star formation main sequence have more evolved stellar populations than those above the main sequence. These results indicate that a fraction of the adv-merger （U）LIRGs have already exhibited signs of fading from the starburst phase and that the NUV-r reddest adv-merger （U）LIRGs are likely at the initial stage of post-starbursts with an age of - 1 Gyr, which is consistent with the gas exhaustion time-scales. Therefore, our results offer additional support for the fast evolutionary track from the blue cloud to the red sequence.
基金the National Key Research and Development Program of China(No.2017YFA0402703)the National Natural Science Foundation of China(Nos.11733002 and 11573017)。
文摘We investigate two classes of conditions for galaxy quenching at 0.510^10 M⊙)have much higher stellar mass surface densities within the central 1 kpc(∑1)and smaller sizes than star-forming galaxies in the same stellar mass range.In addition,the quiescent fractions significantly increase with the increase of∑1 regardless of whether galaxies are centrals or satellites.In contrast,we find that the overall lower-mass quiescent galaxies(M*<~10^10M⊙)have slightly higher E1 and comparable sizes compared to starforming galaxies of the same mass and at the same redshift.At z<1.5,satellites have higher halo masses and larger quiescent fractions than those of centrals at a given∑1(stellar mass).Our findings indicate that the significant growth of the galaxy cores is closely related to the quenching of massive galaxies since z^2.5,while the environmental effect plays an important role in the quenching of low-mass galaxies at z≤1.5.
基金the National Natural Science Foundation ofChina (No. 19873014) and NKBRSFG19990754, and partly by SRF for ROCS, SEM.
文摘We compile a new sample of 89 open clusters with ages, distances and metallicities available. We derive a radial iron gradient of about -0.099±0.008 dex kpc^(-1) (unweighted) for the whole sample, which is somewhat greater than the most recent determination of oxygen gradient from nebulae and young stars. By dividing the clusters into age groups, we show that the iron gradient was steeper in the past and has evolved slowly in time. Current data show a substantial scatter of the cluster metallicities indicating that the Galactic disk has undergone a very rapid, inhomogeneous enrichment. Also, based on a simple, but quite successful model of chemical evolution of the Milky Way disk, we make a detailed calculation of the iron abundance gradient and its time evolution. The predicted current iron gradient is about -0.072 dex kpc^(-1). The model also predicts a steady flattening of the iron gradient with time, which agrees with the result from our open cluster sample.
文摘Understanding galaxy formation is one of the most pressing issues in cos- mology. We review the current status of galaxy formation from both an observational and a theoretical perspective, and summarize the prospects for future advances.
