R-band host galaxy contamination of TeV γ-ray blazar Mrk 501： effects of aperture size and seeing

We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02m optical telescope, managed by Yunnan Observatories, from 2010 May 15 to 18. Based on the host subtraction data usually used in the literature, the subtraction of host galaxy contamination results in significant seeing-brightness correlations. These correlations would lead to illusive large amplitude variations at short timescales, which will mask the intrinsic microvariability, thus giving rise to difficulty in detecting the intrinsic microvariability. Both aperture size and seeing condition influence the flux measurements, but the aperture size impacts the result more significantly. Based on the parameters of an elliptical galaxy provided in the literature, we simulated the host contributions of Mrk 501 in different aperture sizes and seeing conditions. Our simulation data of the host galaxy obviously weaken these significant seeing-brightness correlations for the host-subtracted brightness of Mrk 501, and can help us discover the intrinsic short timescale microvariability. The pure nuclear flux is -8.0 mJy in the R band, i.e., the AGN has a magnitude of R - 13.96 mag.

Comparison of some properties of star forming galaxies and active galactic nuclei between two BOSS galaxy samples from SDSS DR9

Using the LOWZ and CMASS samples of the ninth data release （DR9） from the SDSS-III Baryon Oscillation Spectroscopic Survey （BOSS）, I investigate properties of star forming galaxies and active galactic nuclei （AGNs）. The CMASS sample seriously suffers from the radial selection effect, even within the redshift 0.44 〈 z 〈 0.6, which will likely lead to statistical conclusions in the CMASS sample being less robust. In the LOWZ sample, the fraction of star-forming galaxies is nearly constant from the least dense regime to the densest regime; the AGN fraction is also insensitive to the local environment. In addition, I note that in the LOWZ sample, the distributions of stellar mass and stellar velocity dispersion for star forming galaxies and AGNs are nearly the same.

Comprehensive Study of the Blazars from Fermi-LAT LCR: The Log-Normal Flux Distribution and Linear rms–Flux Relation

Fermi-LAT LCR provides continuous and regularly sampled gamma-ray light curves, spanning about 14 yr, for a large sample of blazars. The log-normal flux distribution and linear rms–flux relation of the light curves for a few Fermi blazars have been examined in previous studies. However, the probability that blazars exhibit the log-normal flux distribution and linear rms–flux relation in their gamma-ray light curves has not been systematically explored.In this study, we comprehensively research the distribution of γ-ray flux and the statistical characteristics on a large sample of 1414 variable blazars from the Fermi-LAT LCR catalog, including 572 FSRQs, 477 BL Lacs, and 365BCUs, and statistically compare their flux distributions with normal and log-normal distributions. The results indicate that the probability of not rejecting log-normal is 42.05% for the large sample, and there is still a 2.05%probability of not rejecting normality, based on the joint of Kolmogorov–Smirnov, Shapiro–Wilk, and Normality tests. We further find that the probability that BL Lacs conform to the log-normal distribution is higher than that of FSRQs. Besides, after removing sources with less than 200 data points from this large sample, a sample of 549blazars, which is still a large sample compared to the previous studies, was obtained. Based on dividing the light curves into segments every 20 points(or 40 points, or one year), we fitted the linear rms–flux relation of these three different sets and found that the Pearson correlation coefficients are all close to 1 for most blazars. This result indicates a strong linear correlation between the rms and the flux of these 549 blazars. The log-normal distribution and linear rms–flux relation indicate that the variability of the γ-ray flux for most blazars is a non-linear and multiplicative process.

The Unusual AGN Host NGC 1266:Evidence for Shocks in a Molecular Gas Rich S0 Galaxy with a Low Luminosity Nucleus

NGC 1266 is a lenticular galaxy(S0)hosting an active galactic nucleus(AGN),and known to contain a large amount of shocked gas.We compare the luminosity ratio of mid-J CO lines to IR continuum with star-forming galaxies(SFGs),and then model the CO spectral line energy distribution(SLED).We confirm that in the mid-and high-J regions(J_(up)=4-13),the C-type shock(v_(s)=25 km s^(-1),n_(H)=5×10^(4)cm^(-3))can reproduce the CO observations well.The galaxy spectral energy distribution(SED)is constructed and modeled by the code X-CIGALE and obtains a set of physical parameters including the star formation rate(SFR,1.17±0.47 M_(⊙)yr^(-1)).Also,our work provides SFR derivation of[C II]from the neutral hydrogen regions only(1.38±0.14 M_(⊙)yr^(-1)).Previous studies have illusive conclusions on the AGN or starburst nature of the NGC 1266 nucleus.Our SED model shows that the hidden AGN in the system is intrinsically low-luminosity,consequently the infrared luminosity of the AGN does not reach the expected level.Archival data from Nu STAR hard X-ray observations in the 3-79 keV band shows a marginal detection,disfavoring presence of an obscured luminous AGN and implying that a compact starburst is more likely dominant for the NGC 1266 nucleus.

Photometric Monitoring of Blazar 3C 66A with the Yunnan University Astronomical Observatory 1 m Telescope

3C 66A is one of our first batches of photometric monitoring objects with the 1 m optical telescope at Yunnan University Astronomical Observatory.In the present work,the observational campaign was performed from 2021 November 1 to 2022 February 27 in the Johnson-Morgan system V and R bands.The average magnitudes in each band were■=15.52±0.18 mag and■=15.07±0.17 mag.The overall variability amplitudes wereΔV=■,Amp=70.27%andΔR=■,Amp=68.56%,respectively.Most of the intraday variabilities(IDVs)occurred in 2021 December and 2022 February.The minimal rise/decay timescale was about 6 minutes(5.82±2.74 minutes and 6.18±2.81 minutes on 2022 February 11,6.99±3.70 minutes and 6.17±2.91 minutes on 2022 February 12).Durations of these rapid variabilities were from 11.99 to 179.67 minutes.The discrete correlation function analyses between V and R bands showed significantly correlated variability.Color index analysis of ID Vs showed that the spectrums do not change with variabilities.

Blazars的多波段辐射谱:聚束效应和内禀谱

考虑了观测到的Ｂｌａｚａｒｓ多波段辐射的两分量特征，提出该观测特征可由频率相并的聚束效应和内禀谱一起来解释．多普勒因子与频率之间的关系由分析观测数据获得．假定内禀谱由非均匀喷流中同步－自康普顿机制产生，应用该模型解释了３Ｃ２７９的辐射．

Blazar的γ射线和低频射电6cm波段辐射关系研究

给出了一个带有射电5 GHz和γ射线辐射流量密度的含有94个γ噪Blazar的大样本,其中有66个FSRQs,20个BL Lac天体,利用该样本研究了射电5 GHz和γ射线流量最大值,最小值以及平均值之间的辐射相关.结果表明:γ射线流量最大值和平均值与射电5GHz辐射有较强的相关,最大相关系数r=0.651,置信度均好于10-4;γ射线流量最小值与射电辐射之间没有相关;3C273辐射的最大值不是爆发态时的观测值,若令γ射线谱指数αG=1.0,则3C273的最大辐射流量为(450.8±39.4)×10-8photon.cm-2.s-1.因此,Blazar的γ射线辐射与低频射电辐射确有关联,γ射线的辐射应来自同步加速自康普顿辐射过程.

γ噪Blazar天体短时标光变的寄主星系影响(英文)

利用云南天文台 1m光学望远镜 2 0 0 0～ 2 0 0 1年对 3个GeV和 /或TeVγ噪Blazar天体的观测 ,发现γ噪类星体PKS 1 51 0 -0 89在R波段有一个光变时标为 4 1min的星等变化为 2 .0mag的剧烈光变 ,这是迄今为止我们所观测到的变幅最大的一个γ噪Blazar天体短时标光变。对此光变 ,可估计限制光变辐射模型的一些参数 ,如辐射区半径R、多普勒因子δ以及吸积转化效率 η等。η =59.6的值强烈预示着相对论聚束效应可较好解释γ噪Blazar天体的辐射机制。我们仔细考察了大气视宁度对光变的影响。发现对 1ES 2 3 44 + 51 4,观测到的光变与当地大气视宁度有一个弱相关 ,结果表明 ,对光变参数较小 (C <5)的光变 ,大气视宁度引起的假光变的贡献较大 。

Four Late-type Galaxies with Double Radio Lobes and Properties of Such Galaxies

The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(La GRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known La GRLs,we confirm the correlation between radio power P_(1.4GHz)and stellar mass M_(*)of host galaxies.Most(25/35)La GRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P_(1.4GHz)-M_(*)relation,and the galaxy color,indicating that bluer galaxies at a fixed M_(*)tend to host more powerful radio lobes.Furthermore,the majority(31/36)of La GRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.

Blazar中央黑洞的变化特性和质量估计

利用ｂｌａｚａｒ的长期的光学和红外测光数据分析了其变化特性，并利用Ｊｕｒｋｅｖｉｃｈ技术和分立相关函数（ＤＣＦ）法在光学数据中寻找光变曲线中的周期性．发现了１．５至１９ｙｒ范围的周期．利用短时间尺度来估计中央黑洞的质量，发现γ射线噪ｂｌａｚａｒ的中心黑洞质量范围为（３．８～１３０） × １０７Ｍ⊙，并对结果作了讨论．

Probing the Gamma-Ray Emission Region of Five TeV Flat Spectrum Radio Quasars

The location ofγ-ray emission of blazars remains a contested topic,inspiring the development of numerous investigative techniques to address this issue.In this work,we analyzed Fermiγ-ray light curves in the GeV and MeV bands,employing the discrete cross-correlation function method to discern time lags between the two bands.For 4C+21.35,Ton 599,B21420+32,and PKS 1510-089,we identified a time lag spanning several days,while for PKS 1441+25,the time lag was not statistically found.The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus in the first four sources,whereas for PKS1441+25,they seem to be sourced mainly from the broad-line region.Further analysis of the opacity(τγγ)and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption.Notably,for PKS 1441+25,the emission region is also posited to lie outside yet proximate to the BLR.The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution with contemporaneous observation data.Our findings suggest that for the five TeV FSRQs,during Te V flaring events,the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources,with the exceptions of 4C+21.35 and PKS1441+25.In terms of the overall jet power,particle energy is the dominant contributor,and the observed blazar radiation cannot be solely attributed to the magnetic field,except in the case of 4C+21.35.Consequently,magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.

Stellar Populations of AGN-host Dwarf Galaxies Selected with Different Methods

In this paper we investigate the stellar populations and star formation histories of 235 active galactic nucleus(AGN)-host dwarf galaxies,consisting of four samples identified separately with different methods(i.e.,radio,X-ray,mid-IR and variability),utilizing the synthesis code STARLIGHT and spectra from the Sloan Digital Sky Survey Data Release 8.Our results show that the variability sample is the oldest,while the mid-IR sample is the youngest,for which the luminosity at 4020?is dominated(>50%)by the young population(t<10~8yr).The light-weighted mean stellar age of the whole sample is in general about 0.7 dex younger than the optical sample studied in Cai et al.We compare the population results between fitting models with and without a power-law(PL)component and find that the neglect of a PL component would lead to an under-and over-estimation by 0.2 and0.1 dex for the light-and mass-weighted mean stellar age,respectively,for our sample of dwarf galaxies,which has a mean fractional contribution of~16%from the AGN.In addition,we obtain further evidence for a possible suppression of star formation in the host galaxy by the central AGN.We also find that there exists an anticorrelation between the extinction-corrected[O III]luminosity and light-weighted mean stellar age,confirming our previous finding that there is a physical connection between AGN and star-forming activities in AGN-host dwarfs.

Relations between the Fractional Variation of the Ionizing Continuum and CⅣBroad Absorption Lines with Different Ionization Levels

This paper explores the correlation between the fractional variation of the ionizing continuum and CⅣbroad absorption lines(BALs)with different ionization levels.Our results reveal anti-correlations between fractional variation of the continuum and fractional equivalency width(EW)variation of the CⅣB ALs without AlⅢB AL/mini-BALs at corresponding velocities,providing evidence for the widespread influence of the ionizing continuum variability on the variation of HiBALs.Conversely,for CⅣBALs accompanied by AlⅢBAL/mini-BALs(LoBAL groups),no significant correction is detected.The absence of such a correlation does not rule out the possibility that variations in these low-ionization lines are caused by ionizing continuum variability,but rather suggests the influence of B AL saturation to some extent.This saturation effect is reflected in the distribution of the fractional EW variation,where the CⅣBAL group accompanied by AlⅢBAL has a smaller standard deviation for the best-fitting Gaussian component than the two BAL groups without AlⅢB AL.However,the distribution of fractional variation of their continuum does not show any significant difference.Besides the saturation influence,another potential explanation for the lack of correlations in the LoBAL groups may be the effects of other variability mechanisms besides the ionization change,such as clouds transiting across the line of sight.

不同类Blazar的红移及谱指数统计特性

从Donato文献中选择了209个B lazar源,其中96个HBL,45个LBL,68个FSRQ.研究了该样本源中3类(HBLs,LBLs,FSRQs)B lazars的红移(z)及X射线谱指数(α)的分布特性,对分布做了K-S检验,比较了3类源的统计特性.结果显示HBLs有较小的红移和较大的X射线谱指数,FSRQs有较大的红移和较小的谱指数,而LBLs居中;3类源之间的红移和谱指数相关在K-S检验中有完全相同的规律.从研究结果可以得出HBL、LBL及FSRQ是有不同物理属性的3类B lazar,HBL与LBL、FSRQ有明显地不同,而LBL与FSRQ却没有明显地不同;LBL似乎是HBL和FS-RQ的中间状态,同时也显示HBL/LBL是较XBL/RBL更好的一种分类方法.

Blazars光变和喷流效应研究进展

活动星系核是当代天体物理研究中最活跃的领域之一.它们对人们探讨星系的形成和演化、宇宙常数的确定、大尺度结构,甚至宇宙各种背景辐射的起源等方面具有非常重要的意义.耀变体是活动星系核的特殊子类,具有极端的观测性质,包括高光度、高而变化的偏振、大幅度激烈光变、视超光速运动和高能伽玛射线辐射.文章将主要介绍光变和喷流效应的研究进展.密集采样捕捉到很短时标,如OJ 287,3C 273,0716+714在光学波段都获得历史最短的光变时标,200 s的快速光变短时标光变发现在PKS 2155-304的Te V波段,而光变周期的分析,多方法加去除伪周期使得结果更加可靠.光变时标在伽玛波段的Doppler因子估算方面取得进展.

Log-normal flux distribution of bright Fermi blazars

We present the results of the γ-ray flux distribution study on the brightest blazars which were observed by Fermi-LAT. We selected 50 of the brightest blazars based on the maximum number of detections reported in the Third LAT AGN Catalog. We performed standard unbinned maximum likelihood analysis on the LAT data during the period between August 2008 and December 2016, in order to obtain the average monthly flux. After quality cuts, blazars for which at least 90% of the total flux had survived were selected for further study, and this included 19 FSRQs and 19 BL Lacs. The Anderson-Darling and χ2 tests suggest that the integrated monthly flux follows a log-normal distribution for all sources, except for three FSRQs for which neither a normal nor a log-normal distribution was preferred. A double log-normal flux distribution tendency was observed in these sources, though this has to be confirmed with improved statistics. We also found that the standard deviation of the log-normal flux distribution increases with the mean spectral index of the blazar, and can be fitted with a line of slope 0.24±0.04. We repeat our study on three additional brightest unclassified blazars to identify their flux distribution properties. Based on the features of their log-normal flux distribution, we infer these unclassified blazars may be closely associated with FSRQs. We also highlight that considering the lognormal behavior of the flux distribution of blazars, averaging their long term flux on a linear scale can largely underestimate the nominal flux and this discrepancy can propagate down to the estimation of source parameters through spectral modeling.

Statistics of Superluminal Motion in Active Galactic Nuclei

We have collected an up-to-date sample of 123 superluminal sources （84 quasars, 27 BL Lac objects and 12 galaxies） and calculated the apparent velocities （βapp） for 224 components in the sources with the A-CDM model. We checked the relationships between their proper motions, redshifts,βapp and 5 GHz flux densities. Our analysis shows that the radio emission is strongly boosted by the Doppler effect. The superluminal motion and the relativistic beaming boosting effect are, to some extent, the same in active galactic nuclei.

Optical quasi-periodic oscillation and color behavior of blazar PKS 2155–304

PKS 2155-304 is a well studied BL Lac object in the southern sky. The historical optical data during different periods have been collected and compiled. Light curves spanning 35 yr have been constructed. The R-band light curve has been ana- lyzed by means of three methods： the epoch folding method, the Jurkevich method and the discrete correlation function method. It is derived that there is an evident periodic component of 317 d （i.e. 0.87 yr） superposed on a long-term trend with large- amplitude variation in the light curve. The variability of this source is accompanied by a slight color variation, and the brightness and color index are correlated with each other. On a long-term time scale, PKS 2155-304 exhibits a tendency of bluer-when- brighter, which means the spectrum becomes flatter when the source brightens.

Spectral energy distributions for TeV blazars

In this work, we collected a sample of 69 TeV blazars from TeVCat, obtained their multi-wavelength observations, and fitted their spectral energy distributions by using a second degree poly-nomial function. The structure parameters of synchrotron bumps for 68 blazars and those of inverse- Compton bumps for 56 blazars were derived. Then, we conducted statistical analysis on the parame-ters （curvature, peak frequency, peak luminosity, bolometric luminosity and X/γ-ray spectral indexes）. From our analysis and discussions, we can conclude the following： （1） There is a clear positive correla-tion between the synchrotron peak frequency, log （Vp）^s, and the inverse-Compton peak frequency, log （Vp）^IC, and between the synchrotron peak luminosity, log （Vp）^sL（Vp）^s, and the inverse-Compton peak luminosity,log（Vp）^IC L（Vp）^IC. （2） The correlation between the peak frequency and the curvature of synchrotron bump is clearly different from that of the inverse-Compton bump, which further indicates that there are differ-ent emission mechanisms between them. （3） There is a correlation between log （Vp）^IC and γ-ray spectral index, αγ, for the TeV blazars： log （Vp）^IC = -（4.59 ± 0.30）αγ ＋ （32.67 ±0.59）, which is consistent with previous work. （4） An ＂L-shape＂ relation is found between log（Vp）^s Up and αx for both TeV blazars and Fermi blazars. A significant correlation between log（Vp）^s and X-ray photon index （αx） is found for the TeV blazars with high synchrotron peak frequency： log（Vp）^s = -（3.20 ± 0.34）αx ＋ （24.33 ± 0.79）, while the correlation is positive for low synchrotron peaked TeV sources. （5） In the αx -αγ diagram, there is also an ＂L-shape.＂ The anti-correlation is consistent with results available in the literature, and we also find a positive correlation between them. （6） Inverse-Compton dominant sources have luminous bolometric luminosities.

Active Optics in LAMOST

Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is one of the major national projects under construction in China. Active optics is one of the most important technologies for new large telescopes. It is used for correcting telescope errors generated by gravitational and thermal changes. Here, however, we use this technology to realize the configuration of LAMOST,—a task that cannot be done in the traditional way. A comprehensive and intensive research on the active optics used in LAMOST is also reported, including an open-loop control method and an auxiliary closed-loop control method. Another important development is in our pre-calibration method of open-loop control, which is with some new features: simultaneous calculation of the forces and displacements of force actuators and displacement actuators; the profile of mirror can be arbitrary; the mirror surface shape is not expressed by a fitting polynomial, but is derived from the mirror surface shape formula which is highly accurate; a proof is given that the solution of the pre-calibration method is the same as the least squares solution.