Subjects: Astronomy >> Galaxy and Cosmology submitted time 2023-12-08
Abstract： This paper presents a morphological investigation of the early-type spiral galaxy M81 (NGC 3031) through decomposition by fitting radial profiles of surface brightness using the software GALFIT, aimed at exploring structural components of M81 and quantifying their morphology. In this work, we adopt 6 types of decompositions with different numbers of morphological components, among which the most complicated one contains 5 components such as a bulge, a disk, a pair of outer spiral arms, a pair of inner spiral arms, and a galactic nucleus. The results show that, M81 hosts a classical bulge with the S´ersic index ∼ 5.0; the morphology and the luminosity for the bulge are almost constant in the different decomposition types. The disk of M81 has the S´ersic index ∼ 1.2 but the morphology and the luminosity are found sensitive to the inclusion of the inner spiral arms in the decomposition or not. The results of this work indicate that the combination of individual substructures has a considerable impact on the morphology of the galaxy as a mixture. On the basis of the results, the usability of the different types of decomposition is suggested in this work. The three-component decomposition, i.e., bulge + disk + nucleus, is applicable to statistics of large samples of galaxies; more complicated decomposition with spiral arms taken into account is suitable for precise measurements of individual galaxies in small samples. This work is based on the single-band Spitzer-The Infrared Array Camera (IRAC) 4.5 µm image. In the future, we will carry out multi-wavelength decomposition, for the purpose of investigating spectral energy distributions and stellar population properties for the galactic substructures, and thereby deduce their formation history and evolution processes.
Peer Review Status:
Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2023-05-24
Abstract： We analyse H(z) parameter data with some conditions by using Lagrange mean value theorem in Calculus. We find that: (1) there exists at least one decelerated phase at 1 σ confidence level in the redshift range (0.38, 0.59); (2) the equation of motion of dark energy may be less than -1 at 1 σ confidence level at some redshifts in the redshift range (1.3, 1.53); (3) there exists at least one accelerated phase at 1 σ confidence level in the redshift range (1.037, 1.944). These results may provide possible evidences for physics beyond Lambda ACDM.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2023-02-21
Qiuhan He
Ran Li
Carlos S. Frenk
James Nightingale
Shaun Cole
Nicola C. Amorisco
Richard Massey
Andrew Robertson
Amy Etherington
Aristeidis Amvrosiadis
Xiaoyue Cao
Abstract： We rederive the number density of intervening line-of-sight haloes relative to lens subhaloes in galaxy-galaxy strong lensing observations, where these perturbers can generate detectable image fluctuations. Previous studies have calculated the detection limit of a line-of-sight small-mass dark halo by comparing the lensing deflection angles it would cause, to those caused by a subhalo within the lens. However, this overly simplifies the difference in observational consequences between a subhalo and a line-of-sight halo. Furthermore, it does not take into account degeneracies between an extra subhalo and the uncertain properties of the main lens. More in keeping with analyses of real-world observations, we regard a line-of-sight halo as detectable only if adding it to a smooth model generates a statistically significant improvement in the reconstructed image. We find that the number density of detectable line-of-sight perturbers has been overestimated by as much as a factor of two in the previous literature. For typical lensing geometries and configurations, very deep imaging is sensitive to twice as many line-of-sight perturbers as subhaloes, but moderate depth imaging is sensitive to only slightly more line-of-sight perturbers than subhaloes.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2023-02-21
Abstract： In this paper we consider the effects of adding curvature in extended cosmologies involving a free-to-vary neutrino sector and different parametrizations of Dark Energy (DE). We make use of the Planck 2018 cosmic microwave background temperature and polarization data, Baryon Acoustic Oscillations and Pantheon type Ia Supernovae data. Our main result is that a non-flat Universe cannot be discarded in light of the current astronomical data, because we find an indication for a closed Universe in most of the DE cosmologies explored in this work. On the other hand, forcing the Universe to be flat can significantly bias the constraints on the equation of state of the DE component and its dynamical nature.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2023-02-21
Abstract： Interstellar (ISM) and circumgalactic medium (CGM) around galaxies are linked to several physical processes that drive galaxy evolution. For example, the X-ray emission from the CGM gas around ellipticals has been linked to the AGN feedback occurring in the host. Upcoming telescopes such as HUBS, with ~ 1 eV resolution, can provide us with deep insights about the hot gas properties of such galaxies thus constrain these processes. In this project, we discuss X-ray emission of the ISM and CGM of elliptical galaxies simulated using MACER code. We generate X-ray emission data from the MACER simulations with various feedback models and produce mock observations for an instrument with high spectral resolution, which is a necessary step of selecting sources for the future observations with planned mission such as HUBS. More importantly, we establish connections between the physics of AGN and stellar feedback with the emission spectra from the ISM and CGM to investigate the possibility of using observations to constrain feedback models. We fit the X-ray spectra from these simulations with standard fitting procedures and compare the retrieved physical properties with their counterparts from the simulations to understand whether the future high-resolution observations can reliably reveal the properties of the gas in the galaxies.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2023-02-21
Y. T. Yan
C. Henkel
K. M. Menten
Y. Gong
H. Nguyen
J. Ott
A. Ginsburg
T. L. Wilson
A. Brunthaler
A. Belloche
J. S. Zhang
N. Budaiev
D.Jeff
Abstract： We report the discovery of widespread maser emission in non-metastable inversion transitions of NH_3 toward various parts of the Sagittarius B2 molecular cloud/star forming region complex: We detect masers in the J,K= (6,3), (7,4), (8,5), (9,6), and (10,7) transitions toward Sgr B2(M) and Sgr B2(N), an NH_3 (6,3) maser in Sgr B2(NS), and NH_3 (7,4), (9,6), and (10,7) masers in Sgr B2(S). With the high angular resolution data of the Karl G. Jansky Very Large Array (JVLA) in A-configuration we identify 18 maser spots. Nine maser spots arise from Sgr B2(N), one from Sgr B2(NS), five from Sgr B2(M), and three in Sgr B2(S). Compared to our Effelsberg single dish data, the JVLA data indicate no missing flux. The detected maser spots are not resolved by our JVLA observations. Lower limits to the brightness temperature are >3000~K and reach up to several 10^5~K, manifesting the lines' maser nature. In view of the masers' velocity differences with respect to adjacent hot molecular cores and/or UCH{\scriptsize II} regions, it is argued that all the measured ammonia maser lines may be associated with shocks caused either by outflows or by the expansion of UCH{\scriptsize II} regions. Overall, Sgr B2 is unique in that it allows us to measure many NH_3 masers simultaneously, which may be essential to elucidate their so far poorly understood origin and excitation.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2023-02-21
Guang Yang
W. N. Brandt
David M. Alexander
Médéric Boquien
Qingling Ni
Casey Papovich
Justin S. Spilker
Fabio Vito
Jonelle L. Walsh
Chengpeng Zhang
Abstract： Recent studies have revealed a strong relation between sample-averaged black-hole (BH) accretion rate (BHAR) and star formation rate (SFR) among bulge-dominated galaxies, i.e., "lockstep" BH-bulge growth, in the distant universe. This relation might be closely related to the BH-bulge mass correlation observed in the local universe. To understand further BH-bulge coevolution, we present ALMA CO(2-1) or CO(3-2) observations of 7 star-forming bulge-dominated galaxies at z=0.5-2.5. Using the ALMA data, we detect significant (>3σ) CO emission from 4 objects. For our sample of 7 galaxies, we measure (or constrain with upper limits) their CO line fluxes and estimate molecular gas masses (M_{gas}). We also estimate their stellar masses (M_{star}) and SFRs by modelling their spectral energy distributions (SEDs). Using these physical properties, we derive the gas-depletion timescales (t_{dep} = M_{gas}/SFR) and compare them with the bulge/BH growth timescales (t_{grow} = M_{star}/SFR \sim M_{BH}/BHAR). Our sample generally has t_{dep} shorter than t_{grow} by a median factor of ≳4, indicating that the cold gas will be depleted before significant bulge/BH growth takes place. This result suggests that the BH-bulge lockstep growth is mainly responsible for maintaining their mass relation, not creating it. We note that our sample is small and limited to z<2.5; JWST and ALMA will be able to probe to higher redshifts in the near future.
Peer Review Status:Awaiting Review
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Astronomy >> Galaxy and Cosmology submitted time 2022-11-03
Abstract：
Based on the consideration of naturalness and physical facts in Einstein's theories of relativity, a nontrivial spacetime physical picture, which has a slight difference from the standard one, is introduced by making a further distinction on the absolute background of spacetime and the relative length or duration of base units of spacetime. In this picture, the coordinate base units in gravity-induced spacetime metric are defined by the standard clock and ruler equipped by the observer, and duplicated onto the every position of the whole universe. In contrast, the local intrinsic base units of spacetime in gravitational field are defined by the length and duration of physical events intervals in the same-type standard clock and ruler which are really located at every position of the universe. In principle, the reading number of the standard clock is counted by the undergone times of unit intervals defined depending on a certain kind of local intrinsic events. But the size of the base units of spacetime is essentially depicted by the length of the line segment, which is cut from the absolute background of spacetime by the local intrinsic events of unit interval. The effect of gravitation is just to change the length of this segment for base spacetime units. On the basis of such a physical picture of spacetime, in a fairly natural way we re-derive a new classical dynamical equation which satisfies a more realistic and moderately general principle of relativity. To further examine this physical picture including of gravitation and spacetime, we finally reinvestigate the physical picture of spacetime in cosmology and propose a more general and rensonable form for cosmological metric.
Peer Review Status:Awaiting Review
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Astronomy >> Galaxy and Cosmology submitted time 2020-09-09
Abstract： Motivated by recent work on rotating black hole shadow [Phys. Rev. D101, 084029 (2020)], we investigate the shadow behaviors of rotating Hayward-de Sitter black hole for static observers at a finite distance in terms of astronomical observables. This paper uses the newly introduced distortion parameter in [arXiv:2006.00685] to describe the shadow's shape quantitatively. We show that the spin parameter would distort shadows and the magnetic monopole charge would increase the degree of deformation. At the same time, the distortion could be relieved because of the cosmological constant and the distortion would increase with the distance from the black hole. Besides, the spin parameter, magnetic monopole charge and cosmological constant increase will cause the shadow to shrink.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2018-04-25
Abstract： The present paper is a continuation and extension of [1] to CLASH clusters. We study the total, the dark matter density profiles, and correlations in a subgroup of CLASH clusters, as we did for the Newman’s clusters. As in the case of Newman clusters, we find that the DM density profile is strongly influenced by interactions with baryons, and the energy and angular momentum transferred from baryons to DM through dynamical friction. The inner slope of the dark matter density profiles of the clusters are usually flatter than the Navarro-Frenk-White profile inner slope, with maximum value -0.79, and minimum -0.30. As in the case of Newman clusters, there are a series of correlations among the slope α of the dark matter profile, and: a. the core radius of clusters; b. the effective radius R e ; c. the mass of the Brightest Central Galaxy (BCG); d. the total baryonic mass, and stellar mass of the clusters. We also found a correlation between the effective radius and the virial mass. The clusters structure, their total and DM density profiles, and the correlations are understood in a double phase scenario. In the first dissipative phase, the BGC forms. In the second dissipationless phase, the interactions between of baryon cluamps with DM through dynamical friction (DF), flattens the DM distribution. The final result of the two phases is the formation of clusters with different DM distribution, inner slopes, and several correlations between characteristic quantities of the clusters
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2018-03-27
Abstract： In this paper, we show how baryonic physics can solve the problem of the striking diversity in dwarf galaxies rotation curves shapes. To this aim, we compare the distribution of galaxies of the SPARC sample, in the plane V 2kpc -V last (being V 2kpc the galaxy rotation velocity at 2 kpc, and V last that outermost one) with that of galaxies that we simulated taking account of baryonic effects. The scatter in the rotation curves in the V 2kpc -V lastplane, and the trend of the SPARC sample’s, and our simulated galaxies’, distribution is in good agreement. The solution of the ”diversity” problem lies in the ability of baryonic process to produce non self-similar haloes, contrary to DM-only simulations. We show also that baryonic effects can reproduce the rotation curves of galaxies like IC2574 characterized by a slow rising with radius. A solution to the diversity problem can be obtained taking appropriately into account the baryon physics effects.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2018-03-27
Abstract： We study how deviations from spherical symmetry of a system, produced by angular momentum, and shear stress, modify the spherical collapse model, as linear density threshold for collapse of the non-relativistic com-ponent (δ c ) and its virial overdensity (∆ V ), in Einstein-de Sitter and ΛCDM models. We modify the sphericalcollapse model to take account of the shear term and angular momentum term. We find that the non-sphericalterms change the non-linear evolution of the system and that the collapse stops “naturally” at the virial ra-dius. Moreover, values of the linear overdensity parameter and of ∆ V are modified with respect to the standard spherical collapse model.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Galaxy and Cosmology submitted time 2016-05-05
Abstract：The South Galactic Cap u-band Sky Survey (SCUSS) is a deep u-band imaging survey in the south Galactic capusing the 2.3 m Bok telescope. The survey observations were completed at the end of 2013, covering an area ofabout 5000 square degrees. We release the data in the region with an area of about 4000 deg2 that is mostly coveredby the Sloan digital sky survey. The data products contain calibrated single-epoch images, stacked images,photometric catalogs, and a catalog of star proper motions derived by Peng et al. The median seeing and magnitudelimit (5σ) are about 2 0 and 23.2 mag, respectively. There are about 8 million objects having measurements ofabsolute proper motions. All the data and related documentations can be accessed through the SCUSS data releasewebsite http://batc.bao.ac.cn/Uband/data.html.Key words: catalogs – surveys – techniques: image processing – techni
Peer Review Status:Awaiting Review
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