arXiv subjects

Jun Ma

Publications and source records attributed to Jun Ma.

At least 469 records · Page 26Linked to original sources

arXiv2012

An updated catalog of M33 clusters and candidates: $UBVRI$ photometry, and some statistical results

We present $UBVRI$ photometry for 392 star clusters and candidates in the field of M33, which are selected from the most recent star cluster catalog. In this catalog, the authors listed star clusters' parameters such as cluster positions, magnitudes and colors in the $UBVRIJHK_s$ filters, and so on. However, a large fraction of objects in this catalog do not have previously published photometry. Photometry is performed using archival images from the Local Group Galaxies Survey, which covers 0.8 deg$^2$ along the major axis of M33. Detailed comparisons show that, in general, our photometry is consistent with previous measurements. Positions (right ascension and declination) for some clusters are corrected here. Combined with previous literature, we constitute a large sample of M33 star clusters. Based on this cluster sample, we present some statistical results: none of the M33 youngest clusters ($\sim 10^7$ yr) have masses approaching $10^5$ $M_{\odot}$; roughly half the star clusters are consistent with the $10^4$ to $10^5$ $M_{\odot}$ mass models; the continuous distribution of star clusters along the model line indicates that M33 star clusters have been formed continuously from the epoch of the first star cluster formation until recent times; there are $\sim 50$ star clusters which being overlapped with the Galactic globular clusters on the color-color diagram, and these clusters are old globular clusters candidates in M33.

astro-ph.CO↗

arXiv2012

Origin of crack pattern in the deposition from drying colloidal suspension

The fracture mechanics was widely employed to explain the crack propagation in the deposition produced by drying colloidal suspension. However, more complex than conventional fracture, those cracks periodically distribute and make up a unique pattern. This still remains mysterious so far. Inspired by the concept of spinodal decomposition, here, we develop the theory to elucidate the spatial arrangement of the cracks, which indicates that the crack pattern is generated by the phase separation of colloidal clusters and water. It concludes that the crack spacing results from the wavelength of the concentration fluctuation during the phase separation, linearly growing with the increase of the deposition thickness and initial particle concentration, which is consistent with experimental results.

cond-mat.soft↗

arXiv2012

Multicolor Photometry of the Nearby Galaxy Cluster A119

This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 (z = 0:0442) with the Beijing-Arizona-Taiwan-Connecticut (BATC) system of 15 intermediate bands. Within the BATC viewing field of 58'* 58', there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies (called sample I). Based on the spectral energy distributions (SEDs) of 1376 galaxies brighter than iBATC = 19:5, photometric redshift technique and the color-magnitude relation of earlytype galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample (called sample II) of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynamically complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidences for morphology and luminosity segregations are found in both samples. With the evolutionary synthesis model PEGASE, environmental effect on the star formation properties is confirmed. Faint galaxies in low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities of interstellar medium, which is in agreement with the context of hierarchical cosmological scenario.

astro-ph.GA↗

arXiv2012

Structural Parameters for Globular Clusters in the Outer Halo of M31

In this paper, we present internal surface brightness profiles, using images in the F606W and F814W filter bands observed with the Advanced Camera for Surveys on the {\it Hubble Space Telescope}, for ten globular clusters (GCs) in the outer halo of M31. Standard King models are fitted to the profiles to derive their structural and dynamical parameters. The results show that, in general, the properties of clusters in M31 and the Milky Way fall in the same regions of parameter spaces. The outer halo GCs of M31 have larger ellipticities than most of GCs in M31 and the Milky Way. Their large ellipticities may be due to galaxy tides coming from satellite dwarf galaxies of M31 or may be related to the apparently more vigorous accretion or merger history that M31 has experienced. The tight correlation of cluster binding energy $E_b$ with mass $M_{\rm mod}$ indicates that, the "fundamental plane" does exist for clusters, regardless of their host environments, which is consistent with previous studies.

astro-ph.CO↗

arXiv2012

Spectroscopic Study of Globular Clusters in the Halo of M31 with Xinglong 2.16m Telescope II: Dynamics, Metallicity and Age

(Abridged) We performed the spectroscopic observations of 11 confirmed GCs in M31 with the Xinglong 2.16m telescope and we mainly focus on the fits method and the metallicity gradient for the M31 GC sample. We analyzed and discussed more about the dynamics, metallicity and age, and their distributions as well as the relationships between these parameters. Eight more confirmed GCs in the halo of M31 were observed, most of which lack the spectroscopic information before. These star clusters are located far from the galactic center at a projected radius of ~14 to ~117 kpc. The Lick absorption-line indices and the radial velocities have been measured and ages, metallicities [Fe/H] and alpha-element [alpha/Fe] have also been fitted by comparing the observed spectral feature indices and Thomas et al.SSP model. Our results show that most of the star clusters of our sample are older than 10 Gyr except B290 ~5.5 Gyr, and most of them are metal-poor with the metallicity [Fe/H]<-1, suggesting that these clusters were born at the early stage of the galaxy's formation. We find that the metallicity gradient for the outer halo clusters with r_p>25 kpc may not exist with a slope of -0.005+-0.005 dex kpc^-1. We also find that the metallicity is not a function of age for the GCs with age < 7 Gyr while for the old GCs with age >7 Gyr there seems to be a trend that the older ones have lower metallicity. Besides, We plot metallicity distributions with the largest sample of M31 GCs so far and it shows the bimodality is not significant and the number of the metal-poor and metal-rich groups becomes comparable. The spatial distributions shows that the metal-rich group is more centrally concentrated while the metal-poor group is occupy a more extended halo and the young population is centrally concentrated while the old population is more extended spatially to the outer halo.

astro-ph.CO↗

arXiv2012

Simultaneous B'V'R' Monitoring of BL Lacertae Object S5~0716+714 and Detection of Inter-Band Time Delay

We present the results of our optical monitoring of the BL Lac object S5 0716+714 on seven nights in 2006 December. The monitoring was carried out simultaneously at three optical wavelengths with a novel photometric system. The object did not show large-amplitude internight variations during this period. Intranight variations were observed on four nights and probably on one more. Strong bluer-when-brighter chromatism was detected on both intranight and internight timescales. The intranight variation amplitude decreases in the wavelength sequence of B', R', and V'. Cross correlation analyses revealed that the variability at the $B'$ and $V'$ bands lead that at the $R'$ band by about 30 minutes on one night.

astro-ph.HE↗

arXiv2011

2MASS photometry and age estimate of globular clusters in the outer halo of M31

We present the first photometric results in J, H, and K_s from 2MASS imaging of 10 classical globular clusters in the far outer regions of M31. Combined with the V and I photometric data from previous literature, we constructed the color-color diagram between J-K_s and V-I. By comparing the integrated photometric measurements with evolutionary models, we estimate the ages of these clusters. The results showed that, all of these clusters are older than $3\times 10^9$ yrs, of which 4 are older than 10 Gyrs and the other 6 are in intermediate ages between 3-8 Gyrs. The masses for these outer halo GCs are from $7.0\times 10^4 M_sun$ to $1.02\times 10^6 M_sun$. We argued that, GC2 and GC3, the ages, metallicities and the distance moduli of which are nearly the same, were accreted from the same satellite galaxy, if they did not form {\it in situ}. The statistical results show that, ages and metallicities for these 10 M31 outer halo GCs do not vary with projected radial position, and the relationship between age and metallicity doest not exit.

astro-ph.CO↗

arXiv2011

Age and structure parameters of a remote M31 globular cluster B514 based on HST, 2MASS, GALEX and BATC observations

B514 is a remote M31 globular cluster which locating at a projected distance of R_p~55 kpc. Deep observations with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) are used to provide the accurate integrated light and star counts of B514. By coupling analysis of the distribution of the integrated light with star counts, we are able to reliably follow the profile of the cluster out to ~40". Based on the combined profile, we study in detail its surface brightness distribution in F606W and F814W filters, and determine its structural parameters by fitting a single-mass isotropic King model. The results showed that, the surface brightness distribution departs from the best-fit King model for r>10". B514 is quite flatted in the inner region, and has a larger half-light radius than majority of normal globular clusters of the same luminosity. It is interesting that, in the M_V versus log R_h plane, B514 lies nearly on the threshold for ordinary globular clusters as defined by Mackey & van den Bergh. In addition, B514 was observed as part of the Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey, using 13 intermediate-band filters covering a wavelength range of 3000--8500 Å. Based on aperture photometry, we obtain its SEDs as defined by the 13 BATC filters. We determine the cluster's age and mass by comparing its SEDs (from 2267 to 20000Å, comprising photometric data in the near-ultraviolet of GALEX, 5 SDSS bands, 13 BATC intermediate-band, and 2MASS near-infrared JHKs} filters) with theoretical stellar population synthesis models, resulting in age of $11.5\pm3.5$ Gyr. This age confirms the previous suggestion that B514 is an old GC in M31. B514 has a mass of $0.96-1.08 \times 10^6 \rm M_sun$, and is a medium-mass globular cluster in M31.

astro-ph.CO↗

arXiv2011

Independent determination of the systematic and random errors of the proper motions in the PPMXL catalog using quasars

Using a sample of 117053 quasars identified in the PPMXL catalog, the systematic errors of the proper motions in the PPMXL catalog are estimated independently as -2.0 and -2.1 mas yr$^{-1}$ in $μ_α\cosδ$ and $μ_δ$, respectively. For objects with SDSS $r$ magnitude between 16.0 and 21.0 mag and SDSS $g-r$ color between -0.4 and 1.2, there are no obvious magnitude and color dependence in the systematic errors of the proper motions in the PPMXL catalog. The random errors of the proper motions in the PPMXL catalog change from $\sim4.0$ to $\sim8.0$ mas yr$^{-1}$ along with the increase of the magnitude of the objects. No color dependence in the random errors of the proper motions in the PPMXL catalog is found. There are obvious right ascension $α$ dependence of the systematic errors in both components of the proper motions in the PPMXL catalog. For quasars with declination $δ>0$, the systematic errors of $μ_δ$ in the PPMXL catalog increase linearly with $δ$ with a slope of 0.07 mas yr$^{-1}$ deg$^{-1}$. For comparison, using a subsample of quasars identified both in the PPMXL and SDSS DR7 catalogs, the systematic errors of the USNO-SDSS proper motions in the SDSS DR7 catalog are derived as 0.9 and 0.5 mas yr$^{-1}$ in $μ_α\cosδ$ and $μ_δ$, respectively. There are no obvious magnitude, color, and $α$ dependence in the systematic errors of the USNO-SDSS proper motions. For quasars with declination $δ>0$, the systematic errors of $μ_δ$ in the SDSS DR7 catalog increase linearly with $δ$ with a slope of 0.03. The random errors of the USNO-SDSS proper motions change from $\sim2.5$ to $\sim6.0$ mas yr$^{-1}$ along with the change of the magnitude and color of the objects.

astro-ph.GA↗

arXiv2011

Spectroscopic Study of Globular Clusters in the Halo of M31 with Xinglong 2.16m Telescope

We present the spectroscopic observations for 11 confirmed globular clusters of M31 with the OMR spectrograph on 2.16m telescope at Xinglong site of National Astronomical Observatories, Chinese Academy of Sciences. Nine of our sample clusters are located in the halo of M31 and the most remote one is out to a projected radius of 78.75 kpc from the galactic center. For all our sample clusters, we measured the Lick absorption-line indices and the radial velocities. It is noted that most GCs of our sample are distinct from the HI rotation curve of M31 galaxy, especially for B514, MCGC5, H12 and B517, suggesting that most of our sample clusters do not have kinematic association with the star forming young disk of the galaxy. We fitted the absorption line indices with the updated stellar population model Thomas et al. (2010) with two different tracks of Cassisi and Padova, separately, by applying the $χ^2-$minimization method. The fitting results show that all our sample clusters are older than 10 Gyr, and metal-poor ($-0.91 \le $ [Fe/H] $\le -2.38$ dex). After merging the spectroscopic metallicity of our work with the previously published ones, we extended the cluster sample out to a projected radius of 117 kpc from the galaxy's center. We found the metallicity gradient for all the confirmed clusters exists with a slope of $-0.028\pm0.001$ dex kpc$^{-1}$. However, the slope turns to be $-0.018\pm0.001$ dex kpc$^{-1}$ for all the halo clusters, which is much shallower. If we only consider the outer halo clusters with $r_{\rm p}>25$ kpc, the slope becomes $-0.010\pm0.002$ dex kpc$^{-1}$ and if one cluster G001 is excluded from the outer halo sample, the slope is $-0.004\pm0.002$ dex kpc$^{-1}$. Thus we conclude that metallicity gradient for M31 outer halo clusters is not significant, which agrees well with the previous findings.

astro-ph.CO↗

arXiv2011

Optical Variability and Colour Behaviour of 3C 345

The colour behaviour of blazars is a subject of much debate. One argument is that the BL Lac objects show bluer-when-brighter chromatism while the flat-spectrum radio quasars (FSRQs) display redder-when-brighter trend. Base on a 3.5-year three-colour monitoring programme, we studied the optical variability and colour behaviour of one FSRQ, 3C 345. There is at least one outburst in this period. The overall variation amplitude is 2.640 mags in the $i$ band. Intra-night variability was observed on two nights. The bluer-when-brighter and redder-when-brighter chromatisms were simultaneously observed in this object when using different pairs of passbands to compute the colours. The bluer-when-brighter chromatism is a shared property with the BL Lacs, while the redder-when-brighter trend is likely due to two less variable emission features, the Mg\,{\sc ii} line and the blue bump, at short wavelengths. With numerical simulations, we show that some other strong but less variable emission lines in the spectrum of FSRQs may also significantly alter their colour behaviour. Then the colour behaviour of an FSRQ is linked not only to the emission process in the relativistic jet, but also to the redshift, the passbands used for computing the colour and the strengths of the less variable emission features relative to the strength of the non-thermal continuum.

astro-ph.CO↗

arXiv2011

Kinematics and Stellar Population Properties of the Andromeda Galaxy by the Spectroscopic Observations of the Guoshoujing Telescope

The Andromeda galaxy was observed by the Guoshoujing Telescope (GSJT, formly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope -- LAMOST) during the 2009 commissioning phase. Due to the absence of standard stars for flux calibration, we use the photometric data of 15 intermediate bands in the Beijing-Arizona-Taipei-Connecticut (BATC) survey to calibrate the spectra. Total 59 spectra located in the bulge and disk of the galaxy are obtained. Kinematic and stellar population properties of the stellar content are derived with these spectra. We obtain the global velocity field and calculate corresponding rotation velocities outer to about 7 kpc along the major axis. These rotation velocity measurements complement those of the gas content, such as the H {\sc i} and CO. The radial velocity dispersion presents that the stars in the bulge are more dynamically thermal and the disk is more rotation-supported. The age distribution shows that the bulge was formed about 12 Gyr ago, the disk is relatively younger, and the ages of some regions along the spiral arms can reach as young as about 1 Gyr. These young stellar populations have relatively richer abundance and larger reddening. The overall average metallicity of the galaxy approximates the solar metallicity and a very weak abundance gradient is gained. The reddening map gives a picture of a dust-free bulge and a distinct dusty ring in the disk.

astro-ph.CO↗

arXiv2011

Stellar Population Properties and Evolution Analysis of NGC 628 with the Panchromatic Photometry

Panchromatic spectral energy distribution (SED) from the ultraviolet (UV), optical to infrared (IR) photometry of NGC 628, combined with the evolutionary stellar population synthesis, is used to derive the spatially resolved age, metallicity and reddening maps. These parameter distributions show that the bulge of this galaxy is a disk-like pseudobulge, which has the S{é}rsic index close to the exponential law, rich gas, and a young circumnuclear ring structure. We also discover the disk has two distinct regions with different radial age and metallicity gradients. The inner region is older and has a much steeper age gradient than the outer region of the disk. Both these two regions and the central young structure can be seen in the radial profile of the optical color. Based on the age and reddening distributions, we consider that the pseudobulge and disk are likely to have grown via the secular evolution, which is the redistribution of mass and energy through the angular momentum transport caused by the non-axisymmetric potential of the spirals. However, possible gas accretion events could affect the outer region of the disk, due to abundant H{\sc i} gas accumulating in the outer disk.

astro-ph.CO↗

arXiv2011

Orbits of nearby planetary nebulae and their interaction with the interstellar medium

We present and analyze the orbits of eight nearby planetary nebulae (PNs) using two different Galactic models. The errors of the derived orbital parameters are determined with a Monte Carlo method. Based on the derived orbital parameters, we find that Sh 2-216, DeHt 5, NGC 7293, A21, and Ton 320 belong to the thin-disk population, and PG 1034+001 and A31 belong to the thick-disk population. PuWe 1 probably belongs to the thick-disk population, but its population classification is very uncertain due to the large errors of its derived orbital parameters. The PN-ISM interactions are observed for the eight PNs in our sample. The position angles of the proper motions of the PNs are consistent with the directions of the PN-ISM interaction regions. The kinematic ages of PNs are much smaller than the time for them to cross the Galactic plane. Using the models of Borkowski et al. and Soker et al., the PN-ISM interaction can be used to derive the local density of ISM in the vicinity of evolved PNs. According to the three-dimensional hydrodynamic simulations of Wareing et al. (WZO), Sh 2-216, A21, and Ton 320 are in the WZO 3 stage, PG 1034+001 and NGC 7293 are in the WZO 1 stage, and PuWe 1 is in the WZO 2 stage.

astro-ph.GA↗

arXiv2011

Multicolor Photometry Study of the Galaxy Cluster A2589: Dynamics, Luminosity Function and Star Formation History

In this paper we present a multicolor photometry for A2589 ($z=0.0414$) with 15 intermediate bands in the Beijing-Arizona-Taiwan-Connecticut (BATC) system which covers an optical wavelength range from 3000 Å to 10000 Å. The spectral energy distributions (SEDs) for more than 5000 sources are achieved down to {\it V} $\sim$ 20 mag in about 1 deg$^{2}$ field. A2589 has been also covered by the Sloan Digital Sky Survey (SDSS) in photometric mode only. A cross-identification of the BATC-detected galaxies with the SDSS photometric catalog achieves 1199 galaxies brighter than $i=19.5$ mag, among which 68 member galaxies with known spectroscopic redshifts are found. After combining the SDSS five-band photometric data and the BATC SEDs, the technique of photometric redshift is applied to these galaxies for selecting faint member galaxies. The color-magnitude relation is taken as a further restriction of early-type cluster galaxies. As a result, 106 galaxies are newly selected as member galaxies. Spatial distribution of member galaxies shows a north-south elongation which agrees with the X-ray brightness profile and the orientation of central cD galaxy, NGC 7647. No substructures are detected on the basis of positions and radial velocities of cluster galaxies, indicating that A2589 is a well-relaxed system. The luminosity function of A2589 exhibits a peak at $M_{R} \sim -20$ mag and a dip at $M_{R} \sim -19 $ mag. The low-density outer regions are the preferred habitat of faint galaxies. With the evolutionary population synthesis model, PEGASE, the environmental effect on the star formation properties for 68 spectroscopically confirmed member galaxies is studied. The outlier faint galaxies tend to have longer time scales of star formation, shorter mean stellar ages, and lower metallicities of interstellar medium, which can be interpreted in the context of hierarchical cosmological scenario.

astro-ph.GA↗

arXiv2011

Age and mass constraints for a young massive cluster in M31 based on spectral-energy-distribution fitting

VDB0-B195D is a massive, blue star cluster in M31. It was observed as part of the Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey using 15 intermediate-band filters covering a wavelength range of 3000--10,000 Å. Based on aperture photometry, we obtain its spectral-energy distribution (SED) as defined by the 15 BATC filters. We apply previously established relations between the BATC intermediate-band and the Johnson-Cousins $UBVRI$ broad-band systems to convert our BATC photometry to the standard system. A detailed comparison shows that our newly derived $VRI$ magnitudes are fully consistent with previous results, while our new $B$ magnitude agrees to within $2σ$. In addition, we determine the cluster's age and mass by comparing its SED (from 3000 to 20,000Å, comprising photometric data in the 15 BATC intermediate bands, optical broad-band $BVRI$, and 2MASS near-infrared $JHK_{\rm s}$ data) with theoretical stellar population synthesis models, resulting in age and mass determinations of $60.0\pm 8.0$~Myr and $(1.1-1.6) \times 10^5 M_\odot$, respectively. This age and mass confirms previous suggestions that VDB0-B195D is a young massive cluster in M31.

astro-ph.CO↗

arXiv2011

Detailed study of B037 based on {\sl HST} images

B037 is of interest because it is both the most luminous and the most highly reddened cluster known in M31. Images of deep observations and of highly spatial resolutions with the Advanced Camera for Surveys on the {\sl HST} firstly show that this cluster is crossed by a dust lane. Photometric data in the F606W and F814W filters obtained in this paper provide that, colors of ($\rm {F606W-F814W}$) in the dust lane are redder $\sim 0.4$ mags than ones in the other regions of B037. The {\sl HST} images show that, this dust lane seems to be contained in B037, not from the M31 disk or the Milky Way. As we know, the formation of dust requires gas with a rather high metallicity. However, B037 has a low metallicity to be $\rm [Fe/H]=-1.07\pm 0.20$. So, it seems improbable that the observed dust lane is physically associated with B037. It is clear that the origin of this dust lane is worthy of future study. In addition, based on these images, we present the precise variation of ellipticity and position angle, and of surface brightness profile, and determine the structural parameters of B037 by fitting a single-mass isotropic King model. In the F606W filter, we derive the best-fitting scale radius, $r_0=0.56\pm0.02\arcsec~(=2.16\pm0.08~\rm{pc})$, a tidal radius, $r_t=8.6\pm0.4\arcsec~(=33.1\pm1.5~\rm{pc})$, and a concentration index $c=\log (r_t/r_0)=1.19\pm0.02$. In the F814W filter, we derive $r_0=0.56\pm0.01\arcsec~(=2.16\pm0.04~\rm{pc})$, $r_t=8.9\pm0.3\arcsec~(=34.3\pm1.2~\rm{pc})$, and $c=\log (r_t/r_0)=1.20\pm0.01$. The extinction-corrected central surface brightness is $μ_0=13.53\pm 0.03~{\rm mag~arcsec^{-2}}$ in the F606W filter, and $12.85\pm 0.03~{\rm mag~arcsec^{-2}}$ in the F814W filter, respectively.

astro-ph.CO↗

arXiv2011

The sky brightness and transparency in i-band at Dome A, Antarctica

The i-band observing conditions at Dome A on the Antarctic plateau have been investigated using data acquired during 2008 with the Chinese Small Telescope ARray. The sky brightness, variations in atmospheric transparency, cloud cover, and the presence of aurorae are obtained from these images. The median sky brightness of moonless clear nights is 20.5 mag arcsec^{-2} in the SDSS $i$ band at the South Celestial Pole (which includes a contribution of about 0.06 mag from diffuse Galactic light). The median over all Moon phases in the Antarctic winter is about 19.8 mag arcsec^{-2}. There were no thick clouds in 2008. We model contributions of the Sun and the Moon to the sky background to obtain the relationship between the sky brightness and transparency. Aurorae are identified by comparing the observed sky brightness to the sky brightness expected from this model. About 2% of the images are affected by relatively strong aurorae.

astro-ph.IM↗