We present new ALMA band-7 data for a sample of six luminous quasars at , powered by fast-growing supermassive black holes (SMBHs) with rather uniform properties: the typical accretion rates and ...black hole masses are and . Our sample consists of three "FIR-bright" sources, which were individually detected in previous Herschel/SPIRE observations, with star formation rates of , and three "FIR-faint" sources for which Herschel stacking analysis implies a typical SFR of ∼400 . The dusty interstellar medium in the hosts of all six quasars is clearly detected in the ALMA data and resolved on scales of ∼2 kpc, in both continuum ( ) and line emission. The continuum emission is in good agreement with the expectations from the Herschel data, confirming the intense SF activity in the quasar hosts. Importantly, we detect companion sub-millimeter galaxies (SMGs) for three sources-one FIR-bright and two FIR-faint, separated by and from the quasar hosts. The -based dynamical mass estimates for the interacting SMGs are within a factor of ∼3 of the quasar hosts' masses, while the continuum emission implies . Our ALMA data therefore clearly support the idea that major mergers are important drivers for rapid early SMBH growth. However, the fact that not all high-SFR quasar hosts are accompanied by interacting SMGs and the gas kinematics as observed by ALMA suggest that other processes may be fueling these systems. Our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid SMBH growth.
ABSTRACT We report Herschel/SPIRE observations of 100 very luminous, optically selected active galactic nuclei (AGNs) at with (erg s−1) ≥ 46.5 , where is λLλ at 1350 . The distribution in is similar ...to the general distribution of Sloan Digital Sky Survey AGNs in this redshift and luminosity interval. We measured star-formation (SF) luminosity, , and SF rate (SFR) in 34 detected sources by fitting combined SF and torus templates, where the torus emission is based on Wide Field Infrared Survey Explorer observations. We also obtained statistically significant stacks for the undetected sources in two luminosity groups. The sample properties are compared with those of very luminous AGNs at . The main findings are: (1) The mean and the median SFRs of the detected sources are and M yr−1, respectively. The mean SFR of the undetected sources is 148 M yr−1. The ratio of SFR to the black hole accretion rate is 80 for the detected sources and less than 10 for the undetected sources. Unlike a sample of sources at z 4.8 that we studied recently, there is no difference in and only a very small difference in between the detected and undetected sources. (2) The redshift distribution of and for the most luminous, redshift 2-7 AGNs are different. Similar to previous studies, the highest are found at z 3. However, the of such sources peaks at z 5. Assuming the objects in our sample are hosted by the most massive galaxies at those redshifts, we find that approximately 2/3 of the hosts are already below the main sequence of SF galaxies at z = 2−3.5. (3) The spectral energy distributions (SEDs) of dusty tori at high redshift are similar to the shapes found in low redshift, low luminosity AGNs. Herschel upper limits put strong constraints on the long wavelength shape of the SED, ruling out several earlier suggested torus templates as applicable for this sample. (4) We find no evidence for a luminosity dependence of the torus covering factor in sources with (erg s−1) = 44−47.5. This conclusion is based on the recognition that the estimated in several earlier studies is highly uncertain and non-uniformally treated. The median covering factors over this range are 0.68 for isotropic dust emission and 0.4 for anisotropic emission.
We present reverberation mapping (RM) results for 17 high-redshift, high-luminosity quasars with good-quality R-band and emission-line light curves. We are able to measure statistically significant ...lags for Ly (11 objects), Si iv (5 objects), C iv (11 objects), and C iii (2 objects). Using our results and previous lag determinations taken from the literature, we present an updated C iv radius-luminosity relation and provide for the first time radius-luminosity relations for Ly , Si iv, and C iii. While in all cases the slopes of the correlations are statistically significant, the zero points are poorly constrained because of the lack of data at the low-luminosity end. We find that the emissivity-weighted distances from the central source of the Ly , Si iv, and C iii line-emitting regions are all similar, which corresponds to about half that of the Hβ region. We also find that 3/17 of our sources show an unexpected behavior in some emission lines, two in the Ly light curve and one in the Si iv light curve, in that they do not seem to follow the variability of the UV continuum. Finally, we compute RM black hole (BH) masses for those quasars with highly significant lag measurements and compare them with C iv single-epoch (SE) mass determinations. We find that the RM-based BH mass determinations seem smaller than those found using SE calibrations.
Abstract
We present rest-frame ultraviolet images of six luminous quasars at
z
∼ 4.8 obtained with the Hubble Space Telescope (HST). These quasars exhibit a wide range of star formation rates (SFRs) ...and lie in a wide range of environments. We carefully model and subtract the point-like quasar emission and investigate the morphology of the underlying host galaxies at kpc scales. The residual images allowed identification of potential companion sources, which enabled us to explore the role of galaxy merger scenarios in the coevolution of the quasars and their hosts. We also search for the mechanism driving extreme SFRs in three of the six quasars. We find that the rate of detection of potential companions to the host galaxies does not follow trends between high- and low-SFR sources; i.e., the HST imaging suggests that both high- and low-SFR sources are found in both dense and sparse galactic environments. The suggested role of major mergers driving extreme SFRs cannot be supported by the multiwavelength data in hand. Three of four companion sources, previously revealed by submillimeter observations, are not detected in the HST images of three of our quasars. An adapted high-resolution imaging strategy focused on high-SFR sources and extended to a larger quasar sample is required in order to determine the role of mergers in the processes of star formation and supermassive black hole growth at high redshift.
Over the past 15 yr, examples of exotic radio-quiet quasars with intrinsically weak or absent broad emission line regions (BELRs) have emerged from large-scale spectroscopic sky surveys. Here, we ...present spectroscopy of seven such weak emission line quasars (WLQs) at moderate redshifts (z = 1.4-1.7) using the X-shooter spectrograph, which provides simultaneous optical and near-infrared spectroscopy covering the rest-frame ultraviolet (UV) through optical. These new observations effectively double the number of WLQs with spectroscopy in the optical rest-frame, and they allow us to compare the strengths of (weak) high-ionization emission lines (e.g., C IV) to low-ionization lines (e.g., Mg II, Hbeta, Halpha) in individual objects. We detect broad Hbeta and Halpha emission in all objects, and these lines are generally toward the weaker end of the distribution expected for typical quasars (e.g., Hbeta has rest-frame equivalent widths ranging from 15-40 A). However, these low-ionization lines are not exceptionally weak, as is the case for high-ionization lines in WLQs. The X-shooter spectra also display relatively strong optical Fe II emission, HbetaFWHM lap 4000 km s super(-1), and significant C IV blueshifts ( approximately 1000-5500 km s super(-1)) relative to the systemic redshift; two spectra also show elevated UV Fe II emission, and an outflowing component to their (weak) Mg II emission lines. These properties suggest that WLQs are exotic versions of "wind-dominated" quasars. Their BELRs either have unusual high-ionization components, or their BELRs are in an atypical photoionization state because of an unusually soft continuum.
We present results from model fitting to the spectral energy distribution (SED) of a homogeneous sample of Seyfert II galaxies drawn from the 12 mu m Galaxy Sample. Imaging and nuclear flux ...measurements are presented in an accompanying paper. Here we add Spitzer/IRS observations to further constrain the SEDs after careful subtraction of a starburst component. We use the library of CLUMPY torus models from Nenkova et al. and also test the two-phase models recently produced by Stalevski et al. We find that photometric and spectroscopic observations in the mid-IR (lambda gap 5 mu m) are crucial to properly constrain the best-fit torus models. Crucially, the derived torus parameters are quite robust when using CLUMPY models, independently of whether or not the sources require an additional blackbody component. Finally, we find no correlation between the torus properties and the presence of circumnuclear or more global star formation.
Abstract We present the rest-frame ultraviolet−optical spectral properties of 65 broad absorption line (BAL) quasars from the Gemini Near Infrared Spectrograph−Distant Quasar Survey (GNIRS-DQS). ...These properties are compared with those of 195 non-BAL quasars from GNIRS-DQS in order to identify the drivers for the appearance of BALs in quasar spectra. In particular, we compare equivalent widths and velocity widths, as well as velocity offsets from systemic redshifts, of principal emission lines. In spite of the differences between their rest-frame ultraviolet spectra, we find that luminous BAL quasars are generally indistinguishable from their non-BAL counterparts in the rest-frame optical band at redshifts 1.55 ≲ z ≲ 3.50. We do not find any correlation between BAL trough properties and the H β -based supermassive black hole masses and normalized accretion rates in our sample. Considering the Sloan Digital Sky Survey quasar sample, which includes the GNIRS-DQS sample, we find that a monochromatic luminosity at rest-frame 2500 Å of ≳10 45 erg s −1 is a necessary condition for launching BAL outflows in quasars. We compare our findings with other BAL quasar samples and discuss the roles that accretion rate and orientation play in the appearance of BAL troughs in quasar spectra.
We present new H- and K-band spectroscopy of 15 high-luminosity active galactic nuclei (AGNs) at redshifts 2.3-3.4 obtained with Gemini South. We combined the data with spectra of an additional 29 ...high-luminosity sources to obtain a sample with 10 super(45.2) < lambda L sub( lambda )(5100 A) < 10 super(47.3) ergs s super(-1) and a black hole (BH) mass range, using reverberation mapping relationships based on the H beta method, of 10 super(8.8)-10 super(10.7) M unk. We do not find a correlation of L/L sub(Edd) with M sub(BH), but we do find a correlation with lambda L sub( lambda )(5100 A), which might be due to selection effects. The L/L sub(Edd) distribution is broad and covers the range of similar to 0.07-1.6, similar to what is observed in lower redshift, lower luminosity AGNs. We suggest that this consistently measured and calibrated sample gives the best representation of L/L sub(Edd) at those redshifts, and note potential discrepancies with recent theoretical and observational studies. The lower accretion rates are not in accord with growth scenarios for BHs at such redshifts, and the growth times of many of the sources are longer than the age of the universe at the corresponding epochs. This suggests earlier episodes of faster growth at z unk 3 for those sources. The use of the C IV lambda 1549 method gives considerably different results and a larger scatter; this method seems to be a poor M sub(BH) and L/L sub(Edd) estimator at very high luminosity.
Abstract
The most reliable single-epoch supermassive black hole mass (
M
BH
) estimates in quasars are obtained by using the velocity widths of low-ionization emission lines, typically the H
β
λ
4861 ...line. Unfortunately, this line is redshifted out of the optical band at
z
≈ 1, leaving
M
BH
estimates to rely on proxy rest-frame ultraviolet (UV) emission lines, such as C
iv
λ
1549 or Mg
ii
λ
2800, which contain intrinsic challenges when measuring, resulting in uncertain
M
BH
estimates. In this work, we aim at correcting
M
BH
estimates derived from the C
iv
and Mg
ii
emission lines based on estimates derived from the H
β
emission line. We find that employing the equivalent width of C
iv
in deriving
M
BH
estimates based on Mg
ii
and C
iv
provides values that are closest to those obtained from H
β
. We also provide prescriptions to estimate
M
BH
values when only C
iv
, only Mg
ii
, and both C
iv
and Mg
ii
are measurable. We find that utilizing both emission lines, where available, reduces the scatter of UV-based
M
BH
estimates by ∼15% when compared to previous studies. Lastly, we discuss the potential of our prescriptions to provide more accurate and precise estimates of
M
BH
given a much larger sample of quasars at 3.20 ≲
z
≲ 3.50, where both Mg
ii
and H
β
can be measured in the same near-infrared spectrum.
Abstract
Astronomical broker systems, such as Automatic Learning for the Rapid Classification of Events (ALeRCE), are currently analyzing hundreds of thousands of alerts per night, opening up an ...opportunity to automatically detect anomalous unknown sources. In this work, we present the ALeRCE anomaly detector, composed of three outlier detection algorithms that aim to find transient, periodic, and stochastic anomalous sources within the Zwicky Transient Facility data stream. Our experimental framework consists of cross-validating six anomaly detection algorithms for each of these three classes using the ALeRCE light-curve features. Following the ALeRCE taxonomy, we consider four transient subclasses, five stochastic subclasses, and six periodic subclasses. We evaluate each algorithm by considering each subclass as the anomaly class. For transient and periodic sources the best performance is obtained by a modified version of the deep support vector data description neural network, while for stochastic sources the best results are obtained by calculating the reconstruction error of an autoencoder neural network. Including a visual inspection step for the 10 most promising candidates for each of the 15 ALeRCE subclasses, we detect 31 bogus candidates (i.e., those with photometry or processing issues) and seven potential astrophysical outliers that require follow-up observations for further analysis.
16
16
The code and the data needed to reproduce our results are publicly available at
https://github.com/mperezcarrasco/AnomalyALeRCE
.
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