We estimate the intrinsic luminosities and synchrotron peak frequencies using the derived Doppler factor for a sample of 170 BL Lac objects, of which the synchrotron peak frequency is derived by fitting the SED constr...We estimate the intrinsic luminosities and synchrotron peak frequencies using the derived Doppler factor for a sample of 170 BL Lac objects, of which the synchrotron peak frequency is derived by fitting the SED constructed with the collected multi-band data from the literature. We find that the debeamed radio and optical core luminosities follow the same correlation found for FR I radio galaxies, which is in support of the unification of the BL Lac objects and the FR I galaxies based on orientation. For the debeamed luminosity at the synchrotron peak frequency, we find a significant positive correlation between the luminosity and intrinsic synchrotron peak frequency. This implies that the more powerful sources may have the majority of jet emission at higher frequency. At the synchrotron peak frequency, the intrinsic luminosity and black hole mass show strong positive correlation, while mild correlation is found in the case of jet power, indicating that the more powerful sources may have more massive black holes.展开更多
We explore the relationship between black hole mass （MBH） and the motion of the jet components for a sample of blazars. The Very Long Baseline Array （VLBA） 2 cm Survey and its continuation： Monitoring of Jets in ...We explore the relationship between black hole mass （MBH） and the motion of the jet components for a sample of blazars. The Very Long Baseline Array （VLBA） 2 cm Survey and its continuation： Monitoring of Jets in active galactic nuclei （AGNs） with VLBA Experiments （MOJAVE） have observed 278 radio-loud AGNs, of which 146 blazars have reliable measurements of their apparent velocities of the jet components. We calculate the minimal Lorentz factors for these sources from their measured apparent velocities, and their black hole masses are estimated with their broad-line widths. A significant intrinsic correlation is found between black hole masses and the minimal Lorentz factors of the jet components. The Eddington ratio is only weakly correlated with the minimal Lorentz factor, which may imply that the Blandford-Znajek （BZ） mechanism may dominate over the Blandford-Payne （BP） mechanism for the jet acceleration （at least） in blazars.展开更多
The entropy of rotating Kerr-Newman-Kasuya black hole due to massive charged fields （bosons and fermions） is calculated by using the new equation of state density motivated by the generalized uncertainty relation. T...The entropy of rotating Kerr-Newman-Kasuya black hole due to massive charged fields （bosons and fermions） is calculated by using the new equation of state density motivated by the generalized uncertainty relation. The result shows the entropy does not depend on the mass and the charge but the parameter A, the area A and the spin of the fields. Moreover, an improved approximation is provided to calculate the scalar entropy.展开更多
Using a simple color selection based on B-, z- and K-band photometry, BzK =（z - K）AB - （B - Z）AB 〉 -0.2, we picked out 52 star-forming galaxies at 1.4 ≤z ≤ 2.5 （sBzKs） from a K-band selected sample （Kvega 〈...Using a simple color selection based on B-, z- and K-band photometry, BzK =（z - K）AB - （B - Z）AB 〉 -0.2, we picked out 52 star-forming galaxies at 1.4 ≤z ≤ 2.5 （sBzKs） from a K-band selected sample （Kvega 〈 22.0） in an area of - 5.5 arcmin^2 of the Hubble Ultra Deep Field （UDF）. We develop a new photometric redshift method, and the error in our photometric redshifts is less than 0.02（1 ＋ z）. From the photometric redshift distribution, we find the BzK color criterion can be used to select star-forming galaxies at 1.4≤ z ≤ 2.5 with Kvega 〈 22.0. Down to Kvega 〈 22.0, the number counts of sBzKs increase linearly with the K magnitude; the sBzKs are strongly clustered, and most of them have irregular morphologies on the ACS images. They have a median reddening of E（B - V） - 0.28, an average star formation rate of - 36 M⊙ yr^-1 and a typical stellar mass of - 10^10 M⊙. The UV criterion for the galaxies at z - 2 can select most of the faint sBzKs in the UDF, but it does not work well for bright, massive, highly-reddened, actively star-forming galaxies.展开更多
New XMM-Newton data of seven Seyfert 2 galaxies with optical spectropolarimetric observations are presented. An analysis of the 0.5 - 10 keV spectra shows that four Seyfert 2 galaxies with polarized broad lines （PBLs...New XMM-Newton data of seven Seyfert 2 galaxies with optical spectropolarimetric observations are presented. An analysis of the 0.5 - 10 keV spectra shows that four Seyfert 2 galaxies with polarized broad lines （PBLs） are absorbed by NH 〈 1024 cm^-2, while two of three Seyfert 2 galaxies without PBLs show evidence of Compton-thick obscuration, supporting the conclusion that Seyfert 2 galaxies without PBLs are more obscured than those with PBLs, Adding the measured obscuration indicators （NH, T ratio, and Fe Kα line EW） of six luminous AGNs to our previous sample improves the significance level of the difference in absorption from 92.3% to 96.3% for NH, 99.1% to 99.4% for T ratio, and 95.3% to 97.4% for Fe Kα line EW. The present results support and enhance the suggestions that the absence of PBLs in Seyfert 2 galaxies can be explained by larger viewing angles of the line of sight to the putative dusty toms, which leads to the obscuration of the broad-line scattering screen, as expected in the unification model.展开更多
The light curve data from 1894 to 2008 are compiled for the BL Lacertae object OJ 287 from the available literature. Periodicity analysis methods （the Discrete Correlation Function-DCF, the Jurkevich method, the powe...The light curve data from 1894 to 2008 are compiled for the BL Lacertae object OJ 287 from the available literature. Periodicity analysis methods （the Discrete Correlation Function-DCF, the Jurkevich method, the power spectral （Fourier） analysis, and the CLEANest method） are performed to search for possible periodicites in the light curve of OJ 287. Significance levels are given for the possible periods. The analysis results confirm the existence of the 12.2 ± 0.6 yr time scale and show a hint of a -53 yr time scale. The 12.2 ± 0.6 yr period is used as the orbital period to investigate the supermassive binary black hole system parameters.展开更多
We present a quantitative study of the classification of Extremely Red Objects （EROs）. The analysis is based on the multi-band spatial- and ground-based observations （HST/ACS-BViz, HST/NICMOS-JH, VLT-JHK） in the H...We present a quantitative study of the classification of Extremely Red Objects （EROs）. The analysis is based on the multi-band spatial- and ground-based observations （HST/ACS-BViz, HST/NICMOS-JH, VLT-JHK） in the Hubble Ultra Deep Field （UDF）. Over a total sky area of 5.50 arcmin2 in the UDF, we select 24 EROs with the color criterion （i - K）vega 〉 3.9, corresponding to （I - K）vega 〉 ～4.0, down to Kvega = 22. We develop four methods to classify EROs into Old passively evolving Galaxies （OGs） and Dusty star-forming Galaxies （DGs）, including （i - K） vs. （J - K） color diagram, spectral energy distribution fitting method, Spitzer MIPS 24 um image matching, and nonparametric measure of galaxy morphology, and found that the classification results from these methods agree well. Using these four classification methods, we classify our EROs sample into 60Gs and 8 DGs to KVega 〈 20.5, and 80Gs and 16 DGs to KVega 〈 22, respectively. The fraction of DGs increases from 8/14 at KVega 〈 20.5 to 16/24 at KVega 〈 22. TO study the morphology of galaxies with its wavelength, we measure the central concentration and the Gini coefficient for the 24 EROs in our sample in HST/ACS-i, z and HST/NICMOS-J, H bands. We find that the morphological parameters of galaxies in our sample depend on the wavelength of observation, which suggests that caution is necessary when comparing single wavelength band images of galaxies at a variety of redshifts.展开更多
We present quasi-simultaneous VLBI images of the GHz-Peaked-Spectrum radio source OQ 208 obtained with the Very Long Baseline Array at 1.4, 1.7, 2.3, 5.0, 8.4, 15.4 GHz and the European VLBI Network at 6.7 GHz. The lo...We present quasi-simultaneous VLBI images of the GHz-Peaked-Spectrum radio source OQ 208 obtained with the Very Long Baseline Array at 1.4, 1.7, 2.3, 5.0, 8.4, 15.4 GHz and the European VLBI Network at 6.7 GHz. The low frequency （1.4, 1.7 and 2.3 GHz） observations reveal a weak and extended steep-spectrum component at about 30 mas away at position angle - 110°, which may be a remnant emission. The radio structure of OQ 208 consists of two mini-lobes at 5.0, 6.7, 8.4 and 15.4 GHz. Our spectral analysis further confirms that the southwest lobe undergoes free-free absorption and finds that the free-free absorption is stronger in the inner region. By fitting the 8.4 GHz images from 1994 to 2005, we obtain a separation speed of 0.0314-0.006 mas yr^-1 between the two mini-lobes. This indicates a jet proper motion of 0.1054-0.020 c and a kinematic age of 219±42 yr for the radio source.展开更多
By employing an improved simulation of the evolution of black holes （BHs） based on the merger tree of dark matter halos, we explore the relationship between the central BH mass Mbh and velocity dispersion σ＊ at hi...By employing an improved simulation of the evolution of black holes （BHs） based on the merger tree of dark matter halos, we explore the relationship between the central BH mass Mbh and velocity dispersion σ＊ at high redshift z ≥ 6 and quantify the mini-QSO＇s （with BH mass M = 200 - 105M⊙） contribution to cosmic reionization. The simulation demonstrates how seed BHs migrate onto the MBH-σ＊ relation by merging with each other and accreting gas at z ≥ 6： 1. The correlation between BHs and their host halos increases as the BHs grow; 2. The slope, i.e. Ф = dlog（Mbh）/dlog（σ＊） in the relationship, is insensitive to the redshift at z 〉 6. In agreement with previous work, we find that mini-QSOs＇ ionizing capability to the Universe lies in the range - 25% - 50% if early miniquasars have extremely high duty cycles, i.e. P（z 〉 6） - 0.9 - 1.展开更多
We present radio images of NRAO 530 on scales ranging from pc to kpc. The observations include the EVN at 5 GHz, the VLBA at 1.6, 8.6 and 15 GHz, the MERLIN at 1.6 and 5 GHz, and the VLA at 5, 8.4, 15, 22, and 43 GHz....We present radio images of NRAO 530 on scales ranging from pc to kpc. The observations include the EVN at 5 GHz, the VLBA at 1.6, 8.6 and 15 GHz, the MERLIN at 1.6 and 5 GHz, and the VLA at 5, 8.4, 15, 22, and 43 GHz. The VLBI images show a core-jet structure with an oscillating trajectory on a scale of about 30 mas north of the strongest compact component （core）. Superluminal motions are detected in five of the jet components with apparent velocities in the range of 13.6 to 25.2c. A new component is detected at 15 GHz with the VLBA observations, which appears to be associated with the outburst in 2002. Significant polarized emission is detected around the core with the VLBA observations at 15 GHz. Rapid variations of the polarization intensity and angle are found between the epochs in 2002 and 2004. On the kpc-scale, a distant component （labelled as WL） located 11 arcsec west （PA=-86°） of the core is detected beyond the core-jet structure which extended to several hundreds of mas in the north-west direction （-50°）. A significant emission between the core-jet structure and the WL is revealed. A clump of diffuse emission （labelled EL, 12 arcsec long） at PA 70° to the core, is also detected in the VLA observations, suggesting the presence of double lobes in the source. The core component shows a fiat spectrum, while the distant components WL and EL have steep spectra. The steep spectra of the distant components and the detection of the arched emission suggest that the distant components are lobes or hot-spots powered by the core of NRAO 530. The morphologies from pc- to kpcscales and the bending of jets are investigated. The observed radio morphology from pc to kcp appears to favor the model in which precession or wobbling of the nuclear disk drives the helical motion of the radio plasma and produces the S-shaped structure on kpc scale.展开更多
基金Supported by the National Natural Science Foundation of ChinaThis work is supported by theNSFC under grants 10373019,10633010 and 10703009
文摘We estimate the intrinsic luminosities and synchrotron peak frequencies using the derived Doppler factor for a sample of 170 BL Lac objects, of which the synchrotron peak frequency is derived by fitting the SED constructed with the collected multi-band data from the literature. We find that the debeamed radio and optical core luminosities follow the same correlation found for FR I radio galaxies, which is in support of the unification of the BL Lac objects and the FR I galaxies based on orientation. For the debeamed luminosity at the synchrotron peak frequency, we find a significant positive correlation between the luminosity and intrinsic synchrotron peak frequency. This implies that the more powerful sources may have the majority of jet emission at higher frequency. At the synchrotron peak frequency, the intrinsic luminosity and black hole mass show strong positive correlation, while mild correlation is found in the case of jet power, indicating that the more powerful sources may have more massive black holes.
基金Supported by the National Natural Science Foundation of China.
文摘We explore the relationship between black hole mass （MBH） and the motion of the jet components for a sample of blazars. The Very Long Baseline Array （VLBA） 2 cm Survey and its continuation： Monitoring of Jets in active galactic nuclei （AGNs） with VLBA Experiments （MOJAVE） have observed 278 radio-loud AGNs, of which 146 blazars have reliable measurements of their apparent velocities of the jet components. We calculate the minimal Lorentz factors for these sources from their measured apparent velocities, and their black hole masses are estimated with their broad-line widths. A significant intrinsic correlation is found between black hole masses and the minimal Lorentz factors of the jet components. The Eddington ratio is only weakly correlated with the minimal Lorentz factor, which may imply that the Blandford-Znajek （BZ） mechanism may dominate over the Blandford-Payne （BP） mechanism for the jet acceleration （at least） in blazars.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10573027 and 10663001, and the Foundation of Shanghai Natural Science Foundation under Grant No 05ZR14138.
文摘The entropy of rotating Kerr-Newman-Kasuya black hole due to massive charged fields （bosons and fermions） is calculated by using the new equation of state density motivated by the generalized uncertainty relation. The result shows the entropy does not depend on the mass and the charge but the parameter A, the area A and the spin of the fields. Moreover, an improved approximation is provided to calculate the scalar entropy.
基金Supported by the National Natural Science Foundation of China.
文摘Using a simple color selection based on B-, z- and K-band photometry, BzK =（z - K）AB - （B - Z）AB 〉 -0.2, we picked out 52 star-forming galaxies at 1.4 ≤z ≤ 2.5 （sBzKs） from a K-band selected sample （Kvega 〈 22.0） in an area of - 5.5 arcmin^2 of the Hubble Ultra Deep Field （UDF）. We develop a new photometric redshift method, and the error in our photometric redshifts is less than 0.02（1 ＋ z）. From the photometric redshift distribution, we find the BzK color criterion can be used to select star-forming galaxies at 1.4≤ z ≤ 2.5 with Kvega 〈 22.0. Down to Kvega 〈 22.0, the number counts of sBzKs increase linearly with the K magnitude; the sBzKs are strongly clustered, and most of them have irregular morphologies on the ACS images. They have a median reddening of E（B - V） - 0.28, an average star formation rate of - 36 M⊙ yr^-1 and a typical stellar mass of - 10^10 M⊙. The UV criterion for the galaxies at z - 2 can select most of the faint sBzKs in the UDF, but it does not work well for bright, massive, highly-reddened, actively star-forming galaxies.
基金the National Natural Science Foundation of China
文摘New XMM-Newton data of seven Seyfert 2 galaxies with optical spectropolarimetric observations are presented. An analysis of the 0.5 - 10 keV spectra shows that four Seyfert 2 galaxies with polarized broad lines （PBLs） are absorbed by NH 〈 1024 cm^-2, while two of three Seyfert 2 galaxies without PBLs show evidence of Compton-thick obscuration, supporting the conclusion that Seyfert 2 galaxies without PBLs are more obscured than those with PBLs, Adding the measured obscuration indicators （NH, T ratio, and Fe Kα line EW） of six luminous AGNs to our previous sample improves the significance level of the difference in absorption from 92.3% to 96.3% for NH, 99.1% to 99.4% for T ratio, and 95.3% to 97.4% for Fe Kα line EW. The present results support and enhance the suggestions that the absence of PBLs in Seyfert 2 galaxies can be explained by larger viewing angles of the line of sight to the putative dusty toms, which leads to the obscuration of the broad-line scattering screen, as expected in the unification model.
基金supported by the National Natural Science Foundation of China (Grant No.10633010)the 973 program(2007CB815405)
文摘The light curve data from 1894 to 2008 are compiled for the BL Lacertae object OJ 287 from the available literature. Periodicity analysis methods （the Discrete Correlation Function-DCF, the Jurkevich method, the power spectral （Fourier） analysis, and the CLEANest method） are performed to search for possible periodicites in the light curve of OJ 287. Significance levels are given for the possible periods. The analysis results confirm the existence of the 12.2 ± 0.6 yr time scale and show a hint of a -53 yr time scale. The 12.2 ± 0.6 yr period is used as the orbital period to investigate the supermassive binary black hole system parameters.
基金supported by the National Natural Science Foundation of China (NSFC, Nos. 10573014, 10633020 and 10873012)the Knowledge InnovationProgram of the Chinese Academy of Science (No. KJCX2-YW-T05)National Basic ResearchProgram of China (973 Program) (No. 2007CB815404).
文摘We present a quantitative study of the classification of Extremely Red Objects （EROs）. The analysis is based on the multi-band spatial- and ground-based observations （HST/ACS-BViz, HST/NICMOS-JH, VLT-JHK） in the Hubble Ultra Deep Field （UDF）. Over a total sky area of 5.50 arcmin2 in the UDF, we select 24 EROs with the color criterion （i - K）vega 〉 3.9, corresponding to （I - K）vega 〉 ～4.0, down to Kvega = 22. We develop four methods to classify EROs into Old passively evolving Galaxies （OGs） and Dusty star-forming Galaxies （DGs）, including （i - K） vs. （J - K） color diagram, spectral energy distribution fitting method, Spitzer MIPS 24 um image matching, and nonparametric measure of galaxy morphology, and found that the classification results from these methods agree well. Using these four classification methods, we classify our EROs sample into 60Gs and 8 DGs to KVega 〈 20.5, and 80Gs and 16 DGs to KVega 〈 22, respectively. The fraction of DGs increases from 8/14 at KVega 〈 20.5 to 16/24 at KVega 〈 22. TO study the morphology of galaxies with its wavelength, we measure the central concentration and the Gini coefficient for the 24 EROs in our sample in HST/ACS-i, z and HST/NICMOS-J, H bands. We find that the morphological parameters of galaxies in our sample depend on the wavelength of observation, which suggests that caution is necessary when comparing single wavelength band images of galaxies at a variety of redshifts.
基金Supported by the National Natural Science Foundation of China.
文摘We present quasi-simultaneous VLBI images of the GHz-Peaked-Spectrum radio source OQ 208 obtained with the Very Long Baseline Array at 1.4, 1.7, 2.3, 5.0, 8.4, 15.4 GHz and the European VLBI Network at 6.7 GHz. The low frequency （1.4, 1.7 and 2.3 GHz） observations reveal a weak and extended steep-spectrum component at about 30 mas away at position angle - 110°, which may be a remnant emission. The radio structure of OQ 208 consists of two mini-lobes at 5.0, 6.7, 8.4 and 15.4 GHz. Our spectral analysis further confirms that the southwest lobe undergoes free-free absorption and finds that the free-free absorption is stronger in the inner region. By fitting the 8.4 GHz images from 1994 to 2005, we obtain a separation speed of 0.0314-0.006 mas yr^-1 between the two mini-lobes. This indicates a jet proper motion of 0.1054-0.020 c and a kinematic age of 219±42 yr for the radio source.
基金partially supported by the National Basic Research Program of China(2009CB824800)the National Natural Science Foundation of China(Grant Nos.10733010,10673010 and 10573016)the Program for New Century Excellent Talents in University
文摘By employing an improved simulation of the evolution of black holes （BHs） based on the merger tree of dark matter halos, we explore the relationship between the central BH mass Mbh and velocity dispersion σ＊ at high redshift z ≥ 6 and quantify the mini-QSO＇s （with BH mass M = 200 - 105M⊙） contribution to cosmic reionization. The simulation demonstrates how seed BHs migrate onto the MBH-σ＊ relation by merging with each other and accreting gas at z ≥ 6： 1. The correlation between BHs and their host halos increases as the BHs grow; 2. The slope, i.e. Ф = dlog（Mbh）/dlog（σ＊） in the relationship, is insensitive to the redshift at z 〉 6. In agreement with previous work, we find that mini-QSOs＇ ionizing capability to the Universe lies in the range - 25% - 50% if early miniquasars have extremely high duty cycles, i.e. P（z 〉 6） - 0.9 - 1.
基金the National Natural Science Foundation of China
文摘We present radio images of NRAO 530 on scales ranging from pc to kpc. The observations include the EVN at 5 GHz, the VLBA at 1.6, 8.6 and 15 GHz, the MERLIN at 1.6 and 5 GHz, and the VLA at 5, 8.4, 15, 22, and 43 GHz. The VLBI images show a core-jet structure with an oscillating trajectory on a scale of about 30 mas north of the strongest compact component （core）. Superluminal motions are detected in five of the jet components with apparent velocities in the range of 13.6 to 25.2c. A new component is detected at 15 GHz with the VLBA observations, which appears to be associated with the outburst in 2002. Significant polarized emission is detected around the core with the VLBA observations at 15 GHz. Rapid variations of the polarization intensity and angle are found between the epochs in 2002 and 2004. On the kpc-scale, a distant component （labelled as WL） located 11 arcsec west （PA=-86°） of the core is detected beyond the core-jet structure which extended to several hundreds of mas in the north-west direction （-50°）. A significant emission between the core-jet structure and the WL is revealed. A clump of diffuse emission （labelled EL, 12 arcsec long） at PA 70° to the core, is also detected in the VLA observations, suggesting the presence of double lobes in the source. The core component shows a fiat spectrum, while the distant components WL and EL have steep spectra. The steep spectra of the distant components and the detection of the arched emission suggest that the distant components are lobes or hot-spots powered by the core of NRAO 530. The morphologies from pc- to kpcscales and the bending of jets are investigated. The observed radio morphology from pc to kcp appears to favor the model in which precession or wobbling of the nuclear disk drives the helical motion of the radio plasma and produces the S-shaped structure on kpc scale.
