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Register a new userOn the Performance of Quasar Reverberation Mapping in the Era of Time-Domain Photometric Surveys
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We quantitatively assess, by means of comprehensive numerical simulations, the ability of broad-band photometric surveys to recover the broad emission line region (BLR) size in quasars under various observing conditions and for a wide range of object properties. Focusing on the general characteristics of the Large Synoptic Survey Telescope (LSST), we find that the slope of the size-luminosity relation for the BLR in quasars can be determined with unprecedented accuracy, of order a few percent, over a broad luminosity range and out to $zsim 3$. In particular, major emission lines for which the BLR size can be reliably measured with LSST include H$alpha$, MgII $lambda 2799$, CIII] $lambda 1909$, CIV $lambda 1549$, and Ly$alpha$, amounting to a total of $gtrsim 10^5$ time-delay measurements for all transitions. Combined with an estimate for the emission line velocity dispersion, upcoming photometric surveys will facilitate the estimation of black hole masses in AGN over a broad range of luminosities and redshifts, allow for refined calibrations of BLR size-luminosity-redshift relations in different transitions, as well as lead to more reliable cross-calibration with other black hole mass estimation techniques.
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A method is proposed for measuring the size of the broad emission line region (BLR) in quasars using broadband photometric data. A feasibility study, based on numerical simulations, points to the advantages and pitfalls associated with this approach. The method is applied to a subset of the Palomar-Green quasar sample for which independent BLR size measurements are available. An agreement is found between the results of the photometric method and the spectroscopic reverberation mapping technique. Implications for the measurement of BLR sizes and black hole masses for numerous quasars in the era of large surveys are discussed.
By using standard broad-band VRI photometry we were able to discriminate the variations of the broad hydrogen alpha line from the continuum variations for the active galaxy Mkn 279. Cross-correlating both light curves enabled us to determine the time lag of the broad line variations behind the continuum and thus to determine the BLR size (about 8 light days). Our preliminary results are rather consistent with the spectroscopic reverberation mapping results (about 12/17 days). This study is a part of an ambitious program to perform photometric reverberation mapping and determine BLR sizes (respectively - the central black hole masses) for more that 100 nearby AGN.
Owing to the advent of large area photometric surveys, the possibility to use broad band photometric data, instead of spectra, to measure the size of the broad line region of active galactic nuclei, has raised a large interest. We describe here a new method using time-delay lensed quasars where one or several images are affected by microlensing due to stars in the lensing galaxy. Because microlensing decreases (or increases) the flux of the continuum compared to the broad line region, it changes the contrast between these two emission components. We show that this effect can be used to effectively disentangle the intrinsic variability of those two regions, offering the opportunity to perform reverberation mapping based on single band photometric data. Based on simulated light curves generated using a damped random walk model of quasar variability, we show that measurement of the size of the broad line region can be achieved using this method, provided one spectrum has been obtained independently during the monitoring. This method is complementary to photometric reverberation mapping and could also be extended to multi-band data. Because the effect described above produces a variability pattern in difference light curves between pairs of lensed images which is correlated with the time-lagged continuum variability, it can potentially produce systematic errors in measurement of time delays between pairs of lensed images. Simple simulations indicate that time-delay measurement techniques which use a sufficiently flexible model for the extrinsic variability are not affected by this effect and produce accurate time delays.
We present results of broad band photometric reverberation mapping (RM) to measure the radius of the broad line region, and subsequently the black hole mass (M$_{rm BH}$), in the nearby, low luminosity active galactic nuclei (AGN) NGC 4395. Using the Wise Observatorys 1m telescope equipped with the SDSS g$$, r$$ and i$$ broad band filters, we monitored NGC 4395 for 9 consecutive nights and obtained 3 light curves each with over 250 data points. The g$$ and r$$ bands include time variable contributions from H$beta$ and H$alpha$ (respectively) plus continuum. The i$$ band is free of broad lines and covers exclusively continuum. We show that by looking for a peak in the difference between the cross-correlation and the auto-correlation functions for all combinations of filters, we can get a reliable estimate of the time lag necessary to compute M$_{rm BH}$. We measure the time lag for H$alpha$ to be $3.6 pm 0.8 $ hours, comparable to previous studies using the line resolved spectroscopic RM method. We argue that this lag implies a black hole mass of M$_{rm BH} = (4.9 pm 2.6) times 10^{4}$ Msun .
The long wavelength modes lost to bright foregrounds in the interferometric 21-cm surveys can partially be recovered using a forward modeling approach that exploits the non-linear coupling between small and large scales induced by gravitational evolution. In this work, we build upon this approach by considering how adding external galaxy distribution data can help to fill in these modes. We consider supplementing the 21-cm data at two different redshifts with a spectroscopic sample (good radial resolution but low number density) loosely modeled on DESI-ELG at $z=1$ and a photometric sample (high number density but poor radial resolution) similar to LSST sample at $z=1$ and $z=4$ respectively. We find that both the galaxy samples are able to reconstruct the largest modes better than only using 21-cm data, with the spectroscopic sample performing significantly better than the photometric sample despite much lower number density. We demonstrate the synergies between surveys by showing that the primordial initial density field is reconstructed better with the combination of surveys than using either of them individually. Methodologically, we also explore the importance of smoothing the density field when using bias models to forward model these tracers for reconstruction.
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