Discovery of Balmer broad absorption lines in the quasar LBQS 1206+1052

We report the discovery of Balmer broad absorption lines （BALs） in the quasar LBQS 1206＋1052 and present a detailed analysis of the peculiar absorption line spectrum. Besides the Mg II λλ2796, 2803 doublet, BALs are also detected in the He I＊ multiplet at λλ2946, 3189, 3889 A arising from the metastable helium 2 3 S level, and in Hα and Hβ from the excited hydrogen H I＊ n = 2 level, which are rarely seen in quasar spectra. We identify two components in the BAL troughs of v ～ 2000 km s 1 width： One component shows an identical profile in H I＊, He I＊ and Mg II with its centroid blueshifted by v c ≈ 726 km s-1 . The other component is detected in He I＊ and Mg II with v c ≈ 1412 km s-1 . We estimate the column densities of H I＊, He I＊, and Mg II, and compare them with possible level population mechanisms. Our results favor the scenario that the Balmer BALs originate in a partially ionized region with a column density of N H ～ 10 21 10 22 cm-2 for an electron density of n e ～ 10 6 10 8 cm-3 via Lyα resonant scattering pumping. The harsh conditions needed may help to explain the rarity of Balmer absorption line systems in quasar spectra. With an i-band PSF magnitude of 16.50, LBQS 1206＋1052 is the brightest Balmer-BAL quasar ever reported. Its high brightness and unique spectral properties make LBQS 1206＋1052 a promising candidate for followup high-resolution spectroscopy, multi-band observations, and long-term monitoring.

Co-variability Between the Broad Absorption Lines and Narrow Absorption Lines

We investigate the relationship between the variability of broad absorption lines(BALs)or narrow absorption lines(NALs)and that of continuum using a data set of two-epoch SDSS spectra containing 134 C IV NAL-BAL pairs.Our analysis reveals an anti-correlation between the fractional equivalent width(EW)variations in NALs(or BALs)and the fractional flux variations of the continuum,with Spearman rank correlation coefficients of r=-0.47(p=1E-08)and r=-0.58(p=1E-13),respectively.In addition,we find a positive correlation between the fractional EW variations in NALs and BALs(r=0.72,p=1E-22),and derive a regression equation ΔEW_(NAL)/<EW_(NAL)>=0.803ΔEW_(BAL)/<EW_(BAL)>+0.008,with an intrinsic scatter of 0.14.These results suggest that the variability in the ionizing continuum may play a significant role in the observed changes in C IV NALs and BALs,supporting the idea of photoionization-driven variability.The co-variability between C IV NALs and BALs may imply that they originate from outflows with similar physical conditions.

The Mg_(Ⅱ)absorption line systems in quasar spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope

Making use of quasar spectra from LAMOST,in the spectral data around the Mg_(Ⅱ)emission lines,research described in this paper has detected 217 Mg_(Ⅱ)narrow absorption lines(NALs)with W_(r)^(λ2796)≥3σ_(w)and W_(r)^(λ2803)≥2σ_(w)in a redshift range of 0.4554≤z_(abs)≤2.1110.For quasars observed by both LAMOST and SDSS,we find that 135 Mg_(Ⅱ)NALs were obviously observed in the LAMOST spectra,347 Mg_(Ⅱ)NALs were were apparent in the SDSS spectra,and 132 Mg_(Ⅱ)NALs were clearly present in both the SDSS and LAMOST spectra.The missed Mg_(Ⅱ)NALs are likely ascribed to low signal-to-noise ratios of corresponding spectra.Among the Mg 11 NALs obviously observed in SDSS or LAMOST spectra,eight Mg 11 NALs were significantly changed with|ΔW_(r)^(λ2796)|≥3σw in time intervals ofΔMJD/(1+z_(em))=359-2819 d.

A broad absorption line outflow associated with the broad emission line region in the quasar SDSS J075133.35+134548.3

We report on the discovery of unusual broad absorption lines(BALs)in the bright quasar SDSS J075133.35+134548.3 at z~1,using archival and newly obtained optical and NIR spectroscopic data.The BALs are detected reliably in HeⅠ*λ3889,HeⅠ*λ10830 and tentatively in AlⅢ,MgⅡ.These BALs show complex velocity structures consisting of two major components:a high-velocity component(HV),with a blueshifted velocity range ofΔv_(HV)~9300--3500 km s^(-1),which can be reliably detected in HeⅠ*λ10830,and tentatively in AlⅢand MgⅡ,whereas it is undetectable in HeⅠ*λ3889;and a low-velocity component(LV),withΔv_(LV)~3500--1800 km s^(-1),is only detected in HeⅠ*λ3889 and HeⅠ*λ10830.With the BALs from different ions,the HV outflowing gas can be constrained to have a density of nH~10^(10.3)-10^(11.4) cm^(-3),a column density of NH~10^(21) cm^(-2)and an ionization parameter of U~10^(-1.83)-10^(-1.72);inferring a distance of RHV~0.5 pc from the central continuum source with a monochromatic luminosityλLλ(5100)=7.0×10^(45)erg s^(-1)at 5100 A.This distance is remarkably similar to that of the normal broad line region(BLR)estimated from reverberation experiments,suggesting association of the BLR and the HV BAL outflowing gas.Interestingly,a blueshifted component is also detected in AlⅢand MgⅡbroad emission lines(BELs),and the AlⅢ/MgⅡof such a BEL component can be reproduced by the physical parameters inferred from the HV BAL gas.The LV BAL gas likely has a larger column density,a higher ionization level and hence a smaller distance than the HV BAL gas.Further spectroscopy with a high S/N ratio and broader wavelength coverage is needed to confirm this to shed new light on the possible connection between BALs and BELs.

Origin and Properties of Strong MgII Quasar Absorption Line Systems

Strong MgII quasar absorption line systems provide us with a useful tool to understand the gas that plays an important role in galaxy formation. In this paper, placing the theories of galaxy formation in a cosmological context, we present semi-analytic models and Monte-Carlo simulations for strong MgII absorbers produced in gaseous galactic haloes and/or galaxy discs. We investigate the redshift path density for the MgII absorption lines and the properties of galaxy/absorber pairs, in particular the anti-correlation between the equivalent width of MgII absorption line and the projected galaxy-to-sightline distance. The simulated result of the mean redshift path density of strong MgII systems is consistent with the observational result. The fraction of strong MgII systems arising from galaxy disks is predicted to be ~ 10% of the total. There exists an anti-correlation between the absorption line equivalent and the projected distance of sightline to galaxy center and galaxy luminosity. We determined that the mean absorbing radius Rabs≈29 h-1 bpc(LB/LB*)0.35. After taking selection effects into consideration, this becomes Rabs ≈38 h-1 bpc(LB/LB*)0.18, which is in good agreement with the observational result. This shows the importance of considering selection effects when comparing models with observations.

Discovery of a variable broad absorption line in the BL Lac object PKS B0138-097

We report the discovery of a broad absorption line （BAL） of - 10^4 km s^-1 in width in the previously known BL Lac object PKS 0138-097, which we tentatively identified as an Mg II BAL. This is the first detection of a BAL, which is sometimes seen in powerful quasars with high accretion rates, in a BL Lac object. The BAL was clearly detected in its spectra spanning two epochs at a high luminosity state taken in the Sloan Digital Sky Survey （SDSS）, while it disappeared in three SDSS spectra taken at a low luminosity state. The BAL and its variability pattern were also found in its historical multi-epoch spectra in the literature, but have been overlooked previously. In its high resolution radio maps, PKS 0138-097 shows a core plus a one- sided parsec-scale jet. The BAL variability can be interpreted as follows： The optical emission is dominated by the core in a high state and by the jet in a low state and the BAL material is located between the core and jet so that the BAL appears only when the core is shining. Our discovery suggests that outflows may also be produced in active galactic nuclei at a low accreting state.

Strong optical and UV intermediate-width emission lines in the quasar SDSS J232444.80–094600.3:dust-free and intermediate-density gas at the skin of dusty torus?

Emission lines from the broad emission line region （BELR） and the narrow emission line region （NELR） of active galactic nuclei （AGNs） have been extensively studied. However, emission lines are rarely detected between these two regions. We present a detailed analysis of quasar SDSS J232444.80-094600.3 （SDSS J2324-0946）, which is remarkable for its strong intermediate-width emission lines （IELs） with FWHM ≈ 1800 km s^-1. The IEL component is present in different emission lines, including the permitted lines Lyαλ1216, CⅣ λ1549, semiforbidden line C Ⅲ] λ1909, and forbidden lines [OⅢ] ss4959, 5007. With the aid of photo-ionization models, we found that the IELs are produced by gas with a hydrogen density of nH - 10^6.2 -- 10^6.3 cm^-3, a distance from the central ionizing source of R - 35 - 50 pc, a covering factor of - 6%, and a dust-to-gas ratio of ≤ 4% that of the SMC. We suggest that the strong IELs of this quasar are produced by nearly dust-free and intermediate-density gas located at the skin of the dusty torus. Such strong IELs, which serve as a useful diagnostic, can provide an avenue to study the properties of gas between the BELR and the NELR.

The redshift number density evolution of Mg Ⅱ absorption systems

We make use of the recent large sample of 17 042 Mg Ⅱ absorption systems from Quider et al. to analyze the evolution of the redshift number density. Regardless of the strength of the absorption line, we find that the evolution of the redshift number density can be clearly distinguished into three different phases. In the intermediate redshift epoch （0.6 ≤ z ≤ 1.6）, the evolution of the redshift number density is consis- tent with the non-evolution curve, however, the non-evolution curve over-predicts the values of the redshift number density in the early （z ≤ 0.6） and late （z ≥ 1.6） epochs. Based on the invariant cross-section of the absorber, the lack of evolution in the red- shift number density compared to the non-evolution curve implies the galaxy number density does not evolve during the middle epoch. The fiat evolution of the redshift number density tends to correspond to a shallow evolution in the galaxy merger rate during the late epoch, and the steep decrease of the redshift number density might be ascribed to the small mass of halos during the early epoch.

A computational method to help identify and measure metallines in high resolution QSO spectra

A computational code is developed to help identify metal absorption lines in high resolution QSO spectra, especially in the Lyα forest. The input to the code includes a list of line central wavelengths, column densities and Doppler widths. The code then searches for candidate metal absorption systems and assesses the probability that each system could be real. The framework of the strategy we employ is described in detail and we discuss how to estimate the errors in line profile fitting that are essential to identification. A series of artificial spectra is constructed to calibrate the performance of the code. Due to the effects of blending and noise on Voigt profile fitting, the completeness of the identification depends on the column density of absorbers. For intermediate and strong artificial metal absorbers, more than 90% could be confirmed by the code. The results of applying the code to the real spectra of QSOs HS0757＋5218 and Q0100＋1300 are also presented.

A very bright (i=16.44) quasar in the ‘redshift desert’ discovered by the Guoshoujing Telescope (LAMOST)

The redshift range from 2.2 to 3 is known as the ＇redshift desert＇ of quasars because quasars with redshifts in this range have similar optical colors as normal stars and are thus difficult to find in optical sky surveys. A quasar candidate, SDSS J085543.40-001517.7, which was selected by a recently proposed criterion involving near-IR Y - K and optical g - z colors, was identified spectroscopically as a new quasar with a redshift of 2.427 by the Guoshoujing Telescope （LAMOST） commissioning observation in 2009 December and confirmed by the observation made with the NAOC/Xinglong 2.16 m telescope in 2010 March. This quasar was not identified in the SDSS spectroscopic survey. Comparing with other SDSS quasars, we found that this new quasar, with an i magnitude of 16.44, is apparently the brightest one in the redshift range from 2.3 to 2.7. From its spectral properties, we derived its central black hole mass to be （1.4 - 3.9） × 10^110 M⊙ and its bolometric luminosity to be 3.7 × 10^48 erg s^-1, which indicates that this new quasar is intrinsically very bright and belongs to the class of the most luminous quasars in the universe. Our identification supports the notion that quasars in the redshift desert can be found by the quasar selection criterion involving the near-IR colors. More missing quasars are expected to be uncovered by future LAMOST spectroscopic surveys, which is important to the study of the cosmological evolution of quasars at redshifts higher than 2.2.

Eight new quasars discovered by the Guoshoujing Telescope (LAMOST) in one extragalactic field

We report the discovery of eight new quasars in one extragalactic field （a five-degree field centered at RA=08^h58^m08.2^s, Dec=01°32′29.7″） with the Guoshoujing Telescope （LAMOST） commissioning observations made on 2009 December 18. These quasars, with i magnitudes from 16.44 to 19.34 and redshifts from 0.898 to 2.773, were not identified in the SDSS spectroscopic survey, though six of them with redshifts less than 2.5 were selected as quasar targets in SDSS. Except for one source without near-IR Y-band data, seven of these eight new quasars satisfy a newly proposed quasar selection criterion involving both near-IR and optical colors. Two of them were found in the ＇redshift desert＇ for quasars （z from 2.2 to 3）, indicating that the new criterion is efficient for uncovering missing quasars with similar optical colors to stars. Although LAMOST encountered some problems during the commissioning observations, we were still able to identify 38 other known SDSS quasars in this field, with i magnitudes from 16.24 to 19.10 and redshifts from 0.297 to 4.512. Our identifications imply that a substantial fraction of quasars may be miss- ing in previous quasar surveys. The implication of our results to the future LAMOST quasar survey is discussed.

New background quasars in the vicinity of the Andromeda Galaxy discovered with the Guoshoujing Telescope (LAMOST)

We present preliminary analyses of spectra of quasar candidates in two Guoshoujing Telescope （GSJT, formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope - LAMOST） test fields near M 31 where one is close to the optical center of the disk and the other is towards the northeastern outskirts of the halo, obtained during the early stage of the GSJT commissioning in the last season of 2009. Both fields contain background low-redshift quasar candidates selected from the SDSS photometry. In total, 14 new quasars with redshifts up to 2 and i magnitudes between 16.7 and 19.2, are discovered, including 7 within the 2.5° central region of M 31. We briefly discuss the potential applications of these newly discovered bright quasars.

Estimating Black Hole Masses of AGNs using Ultraviolet Emission Line Properties

Based on measured broad line region sizes in the reverberation-mapping AGN sample, two new empirical relations are introduced to estimate the central black hole masses of radio-loud high-redshift （z 〉 0.5） AGNs. First, using the archival IUE/HST spectroscopy data at UV band for the reverberation-mapping objects, we obtained two new empirical relations between the BLR size and Mg Ⅱ/C Ⅳ emission line luminosity. Secondly, using the newly determined black hole masses of the reverberation-mapping sample as calibration, we found two new relationships for determining the black hole mass with the full width at half maximum and the luminosity of Mg Ⅱ/C Ⅳ line. We then apply the relations to estimate the black hole masses of the AGNs in the Large Bright Quasar Survey and a sample of radio-loud quasars. For the objects with small radio-loudness, the black hole mass estimated using the RBLR-LMg Ⅱ/C Ⅳ relation is consistent with that from the RBLR-L3000 A/1350 A relation. For radio-loud AGNs, however, the mass estimated from the RBLR-LMg Ⅱ/C Ⅳ relation is systematically lower than that from the continuum luminosity L3000 A/13S0 A Because jets could have significant contributions to the UV/optical continuum luminosity of radio-loud AGNs, we emphasize once again that for radio-loud AGNs, the emission line luminosity may be a better tracer of the ionizing luminosity than the continuum luminosity, so that the relations between the BLR size and UV emission line luminosities should be used to estimate the black hole masses of high redshift radio-loud AGNs.

A search for double-peaked narrow emission line galaxies and AGNs in the LAMOST DR1

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope （LAMOST） has released more than two million spectra, which provide the opportunity to search for double-peaked narrow emission line （NEL） galaxies and active galactic nuclei （AGNs）. The double-peaked narrow-line profiles can be well modeled by two velocity components, respectively blueshifted and redshifted with respect to the sys- temic recession velocity. This paper presents 20 double-peaked NEL galaxies and AGNs found from LAMOST DR1 using a search method based on a multi-Gaussian fit of the narrow emission lines. Among them, ten have already been published by other authors, either listed as genuine double-peaked NEL objects or as asymmetric NEL objects, and the remaining ten are original discoveries. We discuss some pos- sible origins for the double-peaked narrow-line features, such as interaction between jet and narrow line regions, interaction with companion galaxies, and black hole bina- ries. Spatially resolved optical imaging and/or follow-up observations in other spectral bands are needed to further discuss the physical mechanisms at work.

Discovery of two broad absorption line quasars at redshift about 4.75 using the Lijiang 2.4 m telescope

The ultraviolet broad absorption lines have been seen in the spectra of quasars at high redshift, and are generally considered to be caused by outflows with velocities from thousands kilometers per second to one tenth of the speed of light. They provide crucial implications for the cosmological structures and physical evolutions related to the feedback of active galactic nuclei(AGNs).Recently, through a dedicated program of optically spectroscopic identifications of selected quasar candidates at redshift 5 by using the Lijiang 2.4 m telescope, we discovered two luminous broad absorption line quasars(BALQSOs) at redshift about 4.75. One of them may even have the potentially highest absorption Balnicity Index(BI) ever found to date, which is remarkably characterized by its deep, broad absorption lines and sub-relativistic outflows. Further physical properties, including the metal abundances,variabilities, evolutions of the supermassive black holes(SMBH) and accretion disks associated with the feedback process, can be investigated with multi-wavelength follow-up observations in the future.

Quasar SDSS J142507.32+323137.4: dual AGNs?

We analyze the optical spectrum of type 1 QSO SDSS J1425＋3231. This object is interesting since its narrow emission lines, such as [O Ⅲ]λλ4959, 5007, are double-peaked, and the line structure can be modeled well by three Gaussian components： two components for the two peaks （we refer to the peaks at low/high redshift as ＂the blue/red component＂） and another one for the line wing which has the same line center as that of the blue component, but is- 3 times broader. The separation between the blue and red components is -500km s-1 with the blue component being -2 times broader than the red one. The Hβ emission can be separated into four components： two for the double-peaked narrow line and two for the broad line which comes from the broad line regions. The black hole mass estimated from the broad Hβ emission line using the typical reverberation mapping relation is 0.85 × 108 M⊙, which is consistent with that derived from parameters of [O Ⅲ]λ 5007 of the blue component. We suggest that this QSO might be a dual AGN system; the broad Hβ emission line is mainly contributed by the primary black hole （traced by the blue component） while the broad Hβ component of the secondary black hole （traced by the red component） is hard to be separated out considering a resolution of - 2 000 for SDSS spectra or it may be totally obscured by the dusty torus.

The broad wing of the [O Ⅲ] λ5007 emission line in active galactic nuclei

We use a sample of type 2 active galactic nuclei （AGNs） from SDSS DR7 in which the [O Ⅲ] ）λ5007 emission line can be modeled by two Gaussian components, a broad wing plus a narrow core, to investigate the origin of the broad wing and the connection between the velocity shift of the broad wing and the physical parameters of AGNs, as well as their host galaxies. We find that the flux of the wing components is statistically roughly equal to that of the core components. However, the velocity shift of the wing component has only weak, if any, correlations with the physical properties of AGNs and the host galaxies, such as bolometric luminosity, the Eddington ratio, the mass of supermassive black holes, D4000, H3A or stellar mass. Comparing the velocity shift from our type 2 AGN sample to that from the type 1 sample in Zhang et al., we suggest that the [O Ⅲ]] broad wing originates from outflow.

Quasars in the Galactic Anti-Center Area from LAMOST DR3

Abstract We present a sample of quasars discovered in an area near the Galactic Anti-Center covering 150°≤l≤ 210° and ｜b｜ ≤ 30°, based on LAMOST Data Release 3 （DR3）. This sample contains 151 spectroscopically confirmed quasars. Among them 80 are newly discovered with LAMOST. All these quasars are very bright, with i magnitudes peaking around 17.5 mag. All the new quasars were discovered serendipitously from objects that were originally targeted with LAMOST as stars having bluer colors, except for a few candidates targeted as variable, young stellar objects. This bright quasar sample at low Galactic latitudes will help fill the gap in the spatial distribution of known quasars near the Galactic disk that are used to construct an astrometric reference frame for the purpose of accurate proper motion measurements that can be applied to, for example, Gala. They are also excellent tracers to probe the kinematics and chemistry of the interstellar medium in the Milky Way disk and halo via absorption line spectroscopy.

Summary of a Life in Observational Ultraviolet/Optical Astronomy

I reminisce on my early life in Section 1;on my education in Sections 2 and 3;on the years at Princeton as a research astronomer in Section 4;on the years on the faculty at Chicago in Section 5;on research on Diffuse Interstellar Bands(DIBs) in Section 6;on construction of the 3.5 m telescope at Apache Point Observatory(APO)in Section 7;on work on the Sloan Digital Sky Survey(SDSS) in Section 8;on work in public education in Chicago in Section 9;and on my travels in Section 10. My main science research is of an observational nature,concerning Galactic and intergalactic interstellar gas. Highlights for me included my work on the orbiting telescope Copernicus, including the discovery of interstellar deuterium;early observations of absorption associated with fivetimes ionized oxygen;and discoveries concerning the phases of gas in the local interstellar medium, based on previously unobservable interstellar UV spectral lines. With other instruments and collaborations, I extended interstellar UV studies to the intergalactic cool gas using quasi-stellar object QSO absorption lines redshifted to the optical part of the spectrum;provided a better definition of the emission and morphological character of the source of absorption lines in QSO spectra;and pursued the identification of the unidentified DIBs. For several of these topics, extensive collaborations with many scientists were essential over many years. The conclusions developed slowly, as I moved from being a graduate student at Chicago, to a research scientist position at Princeton and then to a faculty position at Chicago. At each stage of life, I was exposed to new technologies adaptable to my science and to subsequent projects. From high school days, I encountered several management opportunities which were formative. I have been extremely fortunate both in scientific mentors I had and in experimental opportunities I encountered.

Quantized Redshift and its Significance for Recent Observation

With the recent observational evidence in extragalactic astronomy,the interpretation of the nature of quasar redshift continues to be a research interest.Very high redshifts are being detected for extragalactic objects that are presumably very distant and young while also exhibiting properties that are characteristic of a more mature galaxy such as ours.According to Halton Arp and Geoffrey Burbidge,redshift disparities consist of an intrinsic component and are related to an evolutionary process.Karlsson observed redshift periodicity at integer multiples of0.089 in log scale and Burbidge observed redshift periodicity at integer multiples of 0.061 in linear scale.Since Singular Value Decomposition based periodicity estimation is known to be superior for noisy data sets,especially when the data contain multiple harmonics and overtones,mainly irregular in nature,we have chosen it to be our primary tool for analysis of the quasar-galaxy pair redshift data.We have observed a fundamental periodicity of0.051 with a confidence interval of 95%in linear scale with the site-available Sloan Digital Sky Survey Data Release 7(SDSS DR7)quasar-galaxy pair data set.We have independently generated quasar-galaxy pair data sets from both 2d F and SDSS and found fundamental periodicities of 0.077 and 0.089,respectively,in log scale with a confidence interval of 95%.