arXiv subjects

Matthias Dietrich

Publications and source records attributed to Matthias Dietrich.

At least 19 recordsLinked to original sources

arXiv2019

The z=0.54 LoBAL Quasar SDSS J085053.12+445122.5: II. The Nature of Partial Covering in the Broad-Absorption-Line Outflow

It has been known for 20 years that the absorbing gas in broad absorption line quasars does not completely cover the continuum emission region, and that partial covering must be accounted for to accurately measure the column density of the outflowing gas. However, the nature of partial covering itself is not understood. Extrapolation of the SimBAL spectral synthesis model of the HST COS UV spectrum from SDSS J0850+4451 reported by Leighly et al. 2018 to non-simultaneous rest-frame optical and near-infrared spectra reveals evidence that the covering fraction has wavelength dependence, and is a factor of 2.5 times higher in the UV than in the optical and near-infrared bands. The difference in covering fraction can be explained if the outflow consists of clumps that are small and either structured or clustered relative to the projected size of the UV continuum emission region, and have a more diffuse distribution on size scales comparable to the near-infrared continuum emission region size. The lower covering fraction over the larger physical area results in a reduction of the measured total column density by a factor of 1.6 compared with the UV-only solution. This experiment demonstrates that we can compare rest-frame UV and near-infrared absorption lines, specifically HeI*10830, to place constraints on the uniformity of absorption gas in broad absorbing line quasars.

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arXiv2018

The z=0.54 LoBAL Quasar SDSS J085053.12+445122.5: I. Spectral Synthesis Analysis Reveals a Massive Outflow

We introduce SimBAL, a novel spectral-synthesis procedure that uses large grids of ionic column densities generated by the photoionization code Cloudy and a Bayesian model calibration to forward-model broad absorption line quasar spectra. We used SimBAL to analyze the HST COS spectrum of the low-redshift BALQ SDSS J085053.12+445122.5. SimBAL analysis yielded velocity-resolved information about the physical conditions of the absorbing gas. We found that the ionization parameter and column density increase, and the covering fraction decreases as a function of velocity. The total log column density is 22.9 (22.4) [cm^-2] for solar (Z=3Z_\odot) metallicity. The outflow lies 1--3 parsecs from the central engine, consistent with the estimated location of the torus. The mass outflow rate is 17--28 M_\odot yr^-1, the momentum flux is consistent with L_Bol/c, and the ratio of the kinematic to bolometric luminosity is 0.8--0.9%. The outflow velocity is similar to the escape velocity at the absorber's location, and force multiplier analysis indicates that part of the outflow could originate in resonance-line driving. The location near the torus suggests that dust scattering may play a role in the acceleration, although the lack of reddening in this UV-selected object indictes a relatively dust-free line of sight. The low accretion rate (0.06 L_Edd) and compact outflow suggests that SDSS~J0850+4451 might be a quasar past its era of feedback, although since its mass outflow is about 8 times the accretion rate, the wind is likely integral to the accretion physics of the central engine.

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arXiv2014

Evidence for AGN Feedback in the Broad Absorption Lines and Reddening of Mrk 231

We present the first J-band spectrum of Mrk 231, which reveals a large \ion{He}{1}*$λ10830$ broad absorption line with a profile similar to that of the well-known \ion{Na}{1} broad absorption line. Combining this spectrum with optical and UV spectra from the literature, we show that the unusual reddening noted by \citet{veilleux13} is explained by a reddening curve like those previously used to explain low values of total-to-selective extinction in SNe Ia. The nuclear starburst may be the origin and location of the dust. Spatially-resolved emission in the broad absorption line trough suggests nearly full coverage of the continuum emission region. The broad absorption lines reveal higher velocities in the \ion{He}{1}* lines (produced in the quasar-photoionized \ion{H}{2} region) compared with the \ion{Na}{1} and \ion{Ca}{2} lines (produced in the corresponding partially-ionized zone). {\it Cloudy} simulations show that a density increase is required between the \ion{H}{2} and partially-ionized zones to produce ionic column densities consistent with the optical and IR absorption line measurements and limits, and that the absorber lies $\sim 100\rm \, pc$ from the central engine. These results suggest that the \ion{He}{1}* lines are produced in an ordinary quasar BAL wind that impacts upon, compresses, and accelerates the nuclear starburst's dusty effluent (feedback in action), and the \ion{Ca}{2} and \ion{Na}{1} lines are produced in this dusty accelerated gas. This unusual circumstance explains the rarity of \ion{Na}{1} absorption lines; without the compression along our line of sight, Mrk~231 would appear as an ordinary FeLoBAL.

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arXiv2014

Tracing the Outflow of a z=0.334 FeLoBAL: New Constraints from Low-Ionization Absorbers in FBQS J1151+3822

We show for the first time that FBQS J1151+3822 is an iron low-ionization broad absorption line quasar (FeLoBAL QSO), the second-brightest and second-closest known example of this class. He I* and Fe II together act as an effective analytical tool, allowing us to obtain useful kinematic constraints from photoionization models of the outflow without needing to assume any particular acceleration model. The main outflow's log ionization parameter is -1.5, the log hydrogen density [cm^(-3)] 5.5 to 8, the log hydrogen column density [cm^(-2)] 21.7 to 21.9, the absorption radius 7.2 to 127 pc, and the kinetic luminosity 0.16% to 4.5% of the bolometric luminosity. We obtain line-of-sight covering fractions of ~0.25 for strong Fe II, ~0.5 for He I*, and ~0.6 for Mg II. Narrower and shallower absorption lines from weaker Fe II and Mn II with outflow velocity ~3400 km/s have appeared between 2005 and 2011, suggesting that dense cores may have condensed inside the main outflow. Consideration of the literature might suggest that the FBQS J1151+3822 outflow is a member of a rare and distinct sub-class of FeLoBALs with high densities and correspondingly small absorption radii. We find, however, that such outflows are not necessarily a distinct sub-class, and that their apparent rarity could be a symptom of selection bias in studies using density-sensitive lines.

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arXiv2013

Strong UV and X-ray variability of the Narrow Line Seyfert 1 Galaxy WPVS 007 -- on the nature of the X-ray low state

We report on multi-wavelength observations of the X-ray transient Narrow Line Seyfert 1 (NLS1) galaxy WPVS 007. The galaxy was monitored with Swift between October 2005 and July 2013, after it had undergone a dramatic drop in its X-ray flux earlier. For the first time, we are able to repeatedly detect this NLS1 in X-rays again. This increased number of detections in the last couple of years may suggest that the strong absorber that has been found in this AGN is starting to become leaky, and may eventually disappear. The X-ray spectra obtained for WPVS 007 are all consistent with a partial covering absorber model. A spectrum based on the data during the extreme low X-ray flux states shows that the absorption column density is of the order of 4 x 10^23 cm^-2 with a covering fraction of 95%. WPVS 007 also displays one of the strongest UV variabilities seen in Narrow Line Seyfert 1s. The UV continuum variability anti-correlates with the optical/UV slope alpha-UV which suggests that the variability primarily may be due to reddening. The UV variability time scales are consistent with moving dust `clouds' located beyond the dust sublimation radius of approximately 20 ld. We present for the first time near infrared JHK data of WPVS 007, which reveal a rich emission-line spectrum. Recent optical spectroscopy does not indicate significant variability in the broad and FeII emission lines, implying that the ionizing continuum seen by those gas clouds has not significantly changed over the last decades. All X-ray and UV observations are consistent with a scenario in which an evolving Broad Absorption Line (BAL) flow obscures the continuum emission. As such, WPVS 007 is an important target for our understanding of BAL flows in low-mass active galactic nuclei (AGN).

astro-ph.HE↗

arXiv2012

Optical Monitoring of the Broad-Line Radio Galaxy 3C390.3

We have undertaken a new ground-based monitoring campaign on the BLRG 3C390.3 to improve the measurement of the size of the BLR and to estimate the black hole mass. Optical spectra and g-band images were observed in 2005 using the 2.4m telescope at MDM Observatory. Integrated emission-line flux variations were measured for Ha, Hb, Hg, and for HeII4686, as well as g-band fluxes and the optical AGN continuum at 5100A. The g-band fluxes and the AGN continuum vary simultaneously within the uncertainties, tau=(0.2+-1.1)days. We find that the emission-line variations are delayed with respect to the variable g-band continuum by tau(Ha)=56.3(+2.4-6.6)days, tau(Hb)=44.3(+3.0_-3.3)days, tau(Hg)=58.1(+4.3-6.1)days, and tau(HeII4686)=22.3(+6.5-3.8)days. The blue and red peak in the double peaked line profiles, as well as the blue and red outer profile wings, vary simultaneously within +-3 days. This provides strong support for gravitationally bound orbital motion of the dominant part of the line emitting gas. Combining the time delay of Ha and Hb and the separation of the blue and red peak in the broad double-peaked profiles in their rms spectra, we determine Mbh_vir=1.77(+0.29-0.31)x10^8Msol and using sigma_line of the rms spectra Mbh_vir=2.60(+0.23-0.31)x10^8Msol for the central black hole of 3C390.3, respectively. Using the inclination angle of the line emitting region the mass of the black hole amounts to Mbh=0.86(+0.19-0.18)x10^9 Msol (peak-separation) and Mbh=1.26(+0.21-0.16)x10^9 Msol (sigma_line), respectively. This result is consistent with the black hole masses indicated by simple accretion disk models to describe the observed double-peaked profiles, derived from the stellar dynamics of 3C390.3, and with the AGN radius-luminosity relation. Thus, 3C390.3 as a radio-loud AGN with a low Eddington ratio, Ledd/Lbol=0.02, follows the same AGN radius-luminosity relation as radio-quiet AGN.

astro-ph.CO↗

arXiv2012

Probing High-Column Outflows in BALQSOs Using Metastable Helium

Outflows are believed to be ubiquitous and fundamentally important in active galaxies. Despite their importance, key physical properties of outflows remain poorly unconstrained; this severely limits study of the acceleration process. It is especially difficult to constrain the column density since most of the lines are saturated. However, column densities can be measured using ions that are expected to be relatively rare in the gas, since they are least likely to be saturated. Phosphorus, specifically the PV doublet at 1118 and 1128A, is generally regarded as a useful probe of high column densities because of its low abundance. We have found that the metastable neutral helium triplet is an equally valuable probe of high column densities in BALQSOs. The significant advantage is that it can be observed in the infrared (HeI*10830) and the optical (HeI*3889) bands from the ground in low-redshift (z<1.2) objects. We report the discovery of the first HeI*10830 BALQSO FBQS J1151+3822, and discuss constraints on the column density obtained from the optical and IR HeI* lines. In addition, a new observation revealing MgII and FeII absorption provides further constraints, and Cloudy modeling of HeI*, MgII, and FeII suggests that the difference between LoBALs and FeLoBALs is column density along the line of sight.

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arXiv2010

The First HeI*λ10830 BALQSO

We report the discovery of the first HeI*λ10830 broad absorption line quasar FBQS J1151+3822. Using new infrared and optical spectra, as well as the SDSS spectrum, we extracted the apparent optical depth profiles as a function of velocity of the 3889A and 10830A HeI* absorption lines. Since these lines have the same lower levels, inhomogeneous absorption models could be used to extract the average true HeI* column density; the log of that number was 14.9. The total hydrogen column density was obtained using Cloudy models. A range of ionization parameters and densities were allowed, with the lower limit on the ionization parameter of log U=-1.4 determined by the requirement that there be sufficient HeI*, and the upper limit on the density of log n=8 determined by the lack of Balmer absorption. Simulated UV spectra showed that the ionization parameter could be further constrained in principle using a combination of low and high ionization lines (such as MgII and PV), but the only density-sensitive line predicted to be observable and not significantly blended was CIIIλ1176. We estimated the outflow rate and kinetic energy, finding them to be consistent but on the high side compared with analysis of other objects. Assuming that radiative line driving is the responsible acceleration mechanism, a force multipler model was constructed. A dynamical argument using the model results strongly constrained the density to be log n >= ~7. Consequently, the log hydrogen column density is constrained to be between 21.7 and 22.9, the mass outflow rate to be between 11 and 56 solar masses per year, the ratio of the mass outflow rate to the accretion rate to be between 1.2 and 5.8, and the kinetic energy to be between 1 and 5 x 10^44 erg/s. We discuss the advantages of using HeI* to detect high-column-density BALQSOs and and measure their properties. (Abridged)

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arXiv2009

Black Hole Masses of Intermediate-Redshift Quasars: Near Infrared Spectroscopy

We present near-infrared spectra of ten luminous, intermediate redshift quasars observed with SofI at the NTT of ESO/La Silla. With these rest-frame optical spectra we probe the Hb -[OIII] emission line region. Using the standard scaling relation involving the width of the Hb line and the continuum luminosity, we measure black hole masses in the range of ~2x10^9 to 10^10 Msol. We also used SDSS spectra to probe MgII2798 and CIV1549 emission lines and used these for black hole mass measurements as well. The massive black holes we observe could not have grown by simple radiatively efficient accretion at the observed accretion rate starting from seeds of up to thousand solar masses. About 10% of the observed black hole mass must have been accumulated by earlier merger events and radiatively inefficient accretion. Radiatively efficient accretion would further grow these BHs to masses of several 10^9 Msol in 2 to 3 e-folding times i.e. in several 10^8yrs. The Hb-based Eddington luminosity ratios are in the range of ~0.2 to ~0.7, with an average of (Lbol/Ledd) = 0.39+-0.05. The Lbol/Ledd ratio distribution follows a log-normal distribution which is consistent with prior studies of quasars with comparable luminosity. The Lbol/Ledd ratio distribution of less luminous quasars tend to be shifted to lower Eddington ratios. We also find that the gas metallicity of the broad-line region is ~3Z/Zsol, using NIII]/OIII] and NV/CIV emission line ratios. We find no correlation of the gas metallicity with the optical FeII emission line strength.

astro-ph.CO↗

arXiv2008

Systematic Uncertainties in Black Hole Masses Determined from Single Epoch Spectra

We explore the nature of systematic errors that can arise in measurement of black hole masses from single-epoch spectra of active galactic nuclei (AGNs) by utilizing the many epochs available for NGC 5548 and PG1229+204 from reverberation mapping databases. In particular, we examine systematics due to AGN variability, contamination due to constant spectral components (i.e., narrow lines and host galaxy flux), data quality (i.e., signal-to-noise ratio, S/N), and blending of spectral features by comparing the precision and accuracy of single-epoch mass measurements to those of recent reverberation mapping studies. We calculate masses by characterizing the broad Hbeta emission line by both the full width at half maximum and the line dispersion and demonstrate the importance of removing narrow emission-line components and host starlight. We find that the reliability of line width measurements rapidly decreases for S/N lower than ~10 to 20 (per pixel) and that fitting the line profiles instead of direct measurement of the data does not mitigate this problem but can, in fact, introduce systematic errors. We also conclude that a full spectral decomposition to deblend the AGN and galaxy spectral features is unnecessary except to judge the contribution of the host galaxy to the luminosity and to deblend any emission lines that may inhibit accurate line width measurements. Finally, we present an error budget which summarizes the minimum observable uncertainties as well as the amount of additional scatter and/or systematic offset that can be expected from the individual sources of error investigated. In particular, we find that the minimum observable uncertainty in single-epoch mass estimates due to variability is <~ 0.1 dex for high S/N (>~ 20 per pixel) spectra.

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arXiv2007

Disparate MgII Absorption Statistics towards Quasars and Gamma-Ray Bursts : A Possible Explanation

We examine the recent report by Prochter et al. (2006) that gamma-ray burst (GRB) sight lines have a much higher incidence of strong MgII absorption than quasar sight lines. We propose that the discrepancy is due to the different beam sizes of GRBs and quasars, and that the intervening MgII systems are clumpy with the dense part of each cloudlet of a similar size as the quasars, i.e. < 10^16 cm, but bigger than GRBs. We also discuss observational predictions of our proposed model. Most notably, in some cases the intervening MgII absorbers in GRB spectra should be seen varying, and quasars with smaller sizes should show an increased rate of strong MgII absorbers. In fact, our prediction of variable MgII lines in the GRB spectra has been now confirmed by Hao et al. (2007), who observed intervening FeII and MgII lines at z=1.48 to be strongly variable in the multi-epoch spectra of z=4.05 GRB060206.

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arXiv2007

NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region

We describe results from a new ground-based monitoring campaign on NGC 5548, the best studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L(5100) = 4.7 x 10^42 ergs s^-1. We determine a rest-frame time lag between flux variations in the continuum and the Hbeta line of 6.3 (+2.6/-2.3) days. Combining our measurements with those of previous campaigns, we determine a weighted black hole mass of M_BH = 6.54 (+0.26/-0.25) x 10^7 M_sun based on all broad emission lines with suitable variability data. We confirm the previously-discovered virial relationship between the time lag of emission lines relative to the continuum and the width of the emission lines in NGC 5548, which is the expected signature of a gravity-dominated broad-line region. Using this lowest luminosity state, we extend the range of the relationship between the luminosity and the time lag in NGC 5548 and measure a slope that is consistent with alpha = 0.5, the naive expectation for the broad line region for an assumed form of r ~ L^alpha. This value is also consistent with the slope recently determined by Bentz et al. for the population of reverberation-mapped AGNs as a whole.

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arXiv2007

Quasar Metal Abundances and Host Galaxy Evolution

Quasars signal a unique phase of galaxy evolution -- when massive spheroids are rapidly being assembled, forming stars and growing their central super-massive black holes. Measurements of the metal abundances around quasars provide unique information about these complex evolutionary processes. Here we provide a brief review of the current status and implications of quasar abundance research.

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arXiv2006

The Mass of the Black Hole in the Seyfert 1 Galaxy NGC 4593 from Reverberation Mapping

We present new observations leading to an improved black hole mass estimate for the Seyfert 1 galaxy NGC 4593 as part of a reverberation-mapping campaign conducted at the MDM Observatory. Cross-correlation analysis of the H_beta emission-line light curve with the optical continuum light curve reveals an emission-line time delay of 3.73 (+-0.75) days. By combining this time delay with the H_beta line width, we derive a central black hole mass of M_BH = 9.8(+-2.1)x10^6 M_sun, an improvement in precision of a factor of several over past results.

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arXiv2006

A Reverberation-Based Mass for the Central Black Hole in NGC 4151

We have undertaken a new ground-based monitoring campaign to improve the estimates of the mass of the central black hole in NGC 4151. We measure the lag time of the broad H beta line response compared to the optical continuum at 5100 A and find a lag of 6.6 (+1.1/-0.8) days. We combine our data with the recent reanalysis of UV emission lines by Metzroth et al. to calculate a weighted mean of the black hole mass, M_BH = 4.57 (+0.57/-0.47) x 10^7 M_sun. The absolute calibration of the black hole mass is based on normalization of the AGN black hole mass - stellar velocity dispersion (M_BH - sigma_*) relationship to that of quiescent galaxies by Onken et al. The scatter in the M_BH - sigma_* relationship suggests that reverberation-mapping based mass measurements are typically uncertain by a factor of 3-4.

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arXiv2006

Black Hole Masses and Eddington Ratios at 0.3<z<4

We study the distribution of Eddington luminosity ratios, L_bol/L_edd, of active galactic nuclei (AGNs) discovered in the AGN and Galaxy Evolution Survey (AGES). We combine H-beta, MgII, and CIV line widths with continuum luminosities to estimate black hole (BH) masses in 407 AGNs, covering the redshift range z~0.3-4 and the bolometric luminosity range L_bol~10^45-10^47 erg/s. The sample consists of X-ray or mid-infrared (24 micron) point sources with optical magnitude R<=21.5 mag and optical emission line spectra characteristic of AGNs. For the range of luminosity and redshift probed by AGES, the distribution of estimated Eddington ratios is well described as log-normal with a peak at L_bol/L_edd ~ 1/4 and a dispersion of 0.3 dex. Since additional sources of scatter are minimal, this dispersion must account for contributions from the scatter between estimated and true BH mass and the scatter between estimated and true bolometric luminosity. Therefore, we conclude that: (1) neither of these sources of error can contribute more than \~0.3 dex rms; and (2) the true Eddington ratios of optically luminous AGNs are even more sharply peaked. Because the mass estimation errors must be smaller than ~0.3 dex, we can also investigate the distribution of Eddington ratios at fixed BH mass. We show for the first time that the distribution of Eddington ratios at fixed BH mass is peaked, and that the dearth of AGNs at a factor ~10 below Eddington is real and not an artifact of sample selection. These results provide strong evidence that supermassive BHs gain most of their mass while radiating close to the Eddington limit, and they suggest that the fueling rates in luminous AGNs are ultimately determined by BH self-regulation of the accretion flow rather than galactic scale dynamical disturbances.

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arXiv2004

Implications of Quasar Black Hole Masses at High Redshifts

We investigated a sample of 15 luminous high-redshift quasars (3.3 < z < 5.1) to measure the mass of their super-massive black holes (SMBH) and compare, for the first time, results based on CIV, MgII, and Hbeta emission lines at high-redshifts. Assuming gravitationally bound orbits as dominant broad-line region gas motion, we determine black hole masses in the range of M_bh = 2 times 10^8 M_sun up to M_bh = 4 times 10^10 M_sun. While the black hole mass estimates based on CIV and Hbeta agree well, MgII typically indicates a factor of $\sim 5 \times$ lower SMBH masses. A flatter slope of the Hbeta radius - luminosity relation, a possibly steeper slope of the MgII radius - luminosity relation, and a slightly larger radius of the MgII BLR than for Hbeta could relax the discrepancy. In spite of these uncertainties, the CIV, MgII, and Hbeta emission lines consistently indicate super-massive black hole masses of several times 10^9 M_sun at redshifts up to z = 5.1. Assuming logarithmic growth by spherical accretion with a mass to energy conversion efficiency of epsilon = 0.1 and an Eddington ratio L_bol / L_edd calculated for each quasar individually, we estimate black hole growth-times of the order of several ~100 Myr which are smaller than the age of the universe at the corresponding redshift. Assuming high-mass seed black holes (M_bh^seed = 10^3 to 10^5 M_sun) the SMBHs in the z = 3.5 quasars began to grow at redshifts z > 4, while for the quasars with z > 4.5 they started at z = 6 to 10. These estimated time scales for forming SMBHs at high redshifts, together with previous studies indicating high quasar metallicities, suggest that the main SMBH growth phase occurs roughly contemporaneously with a period of violent and extensive star formation in proto-galactic nuclei.

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arXiv2004

Active Galactic Nuclei Emission-Line Properties Versus Eddington Ratio

We analyze UV spectra for a large sample of 578 Type 1 AGNs and derive Eddington ratios, L/Ledd, from the bolometric luminosities and emission line widths for each object in the sample. The sample spans 5 orders of magnitude in supermassive black hole (SMBH) mass, 7 orders of magnitude in luminosity, and a redshift range from 0 <= z <= 5. We include a sample of 26 low-redshift Narrow-Line Seyfert 1s (NLS1s) for comparative analysis. The NLS1s have slightly larger than average L/Ledd ratios (and smaller SMBH masses) for their luminosities, but those L/Ledd values are still substantially below the average for luminous quasars. A large fraction (27%) of the objects overall have L/Ledd > 1, which might be explained by non-spherically symmetric accretion. We find no trend between L/Ledd and either redshift or SMBH mass. Composite spectra sorted by L/Ledd show an unusual emission-line behavior: nearly constant peak heights and decreasing FWHMs with increasing L/Ledd. This is in marked contrast to the emission-line behaviors with luminosity, SMBH mass, and FWHM(C IV), which clearly show trends analogous to the Baldwin Effect: decreasing line peaks and equivalent widths with increasing luminosity, SMBH mass, and FWHM. The origins of the unusual behavior with L/Ledd are not understood, but one implication is that metallicity estimates based on emission line ratios involving nitrogen show no trend with L/Ledd in the composite spectra created from different ranges in L/Ledd. The NLS1 composite, however, shows a slightly high metallicity for its SMBH mass and luminosity. Our earlier work suggests that host galaxy mass, correlated with SMBH mass and AGN luminosity, is the fundamental parameter affecting BLR metallicities. Some secondary effect, not related to L/Ledd, must be enhancing the metallicities in NLS1s.

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