diff --git a/whitepaper/AGN/AGN_BELR.tex b/whitepaper/AGN/AGN_BELR.tex index 273c7e5..4b60823 100644 --- a/whitepaper/AGN/AGN_BELR.tex +++ b/whitepaper/AGN/AGN_BELR.tex @@ -68,6 +68,8 @@ \subsubsection{Target measurements and discoveries} %parameters, we can anticipate some of the sensitivity of the %photometric RM method to observing strategy.} +% LSST Review by Niel Brandt: how to address selection bias towards high line strength systems? + The PRM method is very sensitive to the sampling in each band, therefore the ability to derive reliable time delays can be affected significantly by the LSST cadence. The best results will be obtained @@ -142,7 +144,7 @@ \subsubsection{Metrics} % \item[Q1:] {\it Does the science case place any constraints on the % tradeoff between the sky coverage and coadded depth? For example, should % the sky coverage be maximized (to $\sim$30,000 deg$^2$, as e.g., in -% Pan-STARRS) or the number of detected galaxies (the current baseline +% Pan-STARRS) or the number of detected galaxies (the current baseline % of 18,000 deg$^2$)?} % % \item[A1:] ... diff --git a/whitepaper/AGN/AGN_Census.tex b/whitepaper/AGN/AGN_Census.tex index b342d6d..c3549d0 100644 --- a/whitepaper/AGN/AGN_Census.tex +++ b/whitepaper/AGN/AGN_Census.tex @@ -20,7 +20,7 @@ \section{AGN Selection and Census}\label{sec:AGNCensus} \credit{AstroVPK}, \credit{ScottAnderson} -The basic figure of merit for AGN science is the total number of AGNs +One basic figure of merit for AGN science is the total number of AGNs discovered in the entire LSST survey, as a function of luminosity and redshift. The main goal is therefore to adjust the Observing Strategy in order to maximize this number. @@ -52,9 +52,9 @@ \subsection{Target measurements and discoveries} observations using two different filters for a particular LSST field. This will eventually determine the AGN $L-z$ distribution and, in particular, may affect the identification of quasars at $z\gtsim 6$ if, for example, $Y$-band exposures -will not be sufficiently deep. +are not sufficiently deep. -{\bf Variability:} AGNs can be effectively distinguished from (variable) +{\bf Variability:} some AGNs can be effectively distinguished from (variable) stars, and from quiescent galaxies, by exhibiting certain characteristic variability patterns (e.g., \citealt{ButlerandBloom2011}). Picking the right cadence can increase the effectiveness of AGN selection. Ultimately, @@ -69,7 +69,7 @@ \subsection{Target measurements and discoveries} {\bf Astrometry:} In cases where selection by color and variability is insufficient for a reliable identification, AGNs can be further selected among sources having zero proper motion, within the uncertainties. The -LSST cadence may affect the level of this uncertainty in each band, and +LSST cadence may affect the level of this uncertainty in each band, and certainly the temporal baseline for proper motion measurement, and may therefore affect the ability to identify (mostly fainter) AGN. % Differential chromatic refraction (DCR), making use of the astrometric offset a @@ -78,7 +78,7 @@ \subsection{Target measurements and discoveries} photometric redshifts \citep{KaczmarczikEtal2009}. The DCR effect is more pronounced at higher airmasses. Therefore, it could be advantageous to have at least one visit, per source, at airmass greater than about 1.4 (though of course -there are trade-offs versus the additional extinction, for faint sources). AGN +there is a trade-off with the additional extinction, for faint sources). AGN selection and photometric redshift confirmation may be affected since the LSST cadence will affect the airmass distribution, in each band, for each AGN candidate. @@ -116,7 +116,7 @@ \subsection{Metrics} 2) Estimate the {\bf number of quasars at $z>6$ that LSST can discover} during a single visit, as well as in the entire survey, and verify that -these numbers do not fall short of the original predictions. This +these numbers do not fall short of the original predictions. To first order this simply requires computing the maximum depth in the $Y$-band (for both single visits and the coadd), averaged across the sky for the nominal OpSim, as well as assessing the ability to reject L and T dwarfs via astrometry. @@ -131,9 +131,11 @@ \subsection{Metrics} The aim is to assess the sizes of the ellipses and how these sizes could be minimized by perturbing the current cadence. -4) Asses how the sampling affects the selection of AGN by variability (e.g., +4) Assess how the sampling affects the selection of AGN by variability (e.g., interactions with red-noise power spectrum). +5) Check how overall survey length affects proper motion measurements and consequently AGN selection. + %4) Estimate the number of low-luminosity AGN (LLAGN) that can be %identified during the entire survey. @@ -154,6 +156,7 @@ \subsection{OpSim Analysis} \label{fig:zgt6} \end{figure} +% LSST Review from Niel Brandt: check for updates needed to this figure, as it is over a decade old. Also, add a plot comparing LSST and WFIRST for high-z AGN selection For assessing the limitations of DCR on the $L-z$ plane of LSST AGNs, one needs to obtain from OpSim the current maximal airmasses for each band, @@ -199,6 +202,7 @@ \subsection{OpSim Analysis} As for general AGN selection, the effects of the sampling on variability selection should be assessed, and the amplitudes of the uncertainties in color-color space and how these depend on the cadence should be simulated. +The combination of LSST photometry with that from WFIRST and/or Euclid data should also be considered, both for extending the upper limit in detectable redshift to $\sim10$, but also improving the completeness and purity of the sample at lower redshifts. % % -------------------------------------------------------------------- % @@ -242,7 +246,7 @@ \subsection{Conclusions} the relative selection completeness and efficiency for OpSim outputs with different uniformity/frequency of sampling. The same can be said for constraining the fraction of observing time in each band (where $u$ -is the most important for $z<\sim3$ and $Y$ is most important for $z>\sim6$) +is the most important for $z\lesssim3$ and $Y$ is most important for $z\gtrsim6$) and for determining whether nightly visits should be in the same band or not, and for the trade-off of single-visit depth and number of visits. However, the AGN census is @@ -252,7 +256,7 @@ \subsection{Conclusions} Galactic plane coverage (spatial coverage, temporal sampling, visits per band)?} -\item[A4:] Given the desire for maximal area, added Galactic plane +\item[A4:] Given the desire for maximal extragalactic area, added Galactic plane coverage would be detrimental to AGN science. \item[Q6:] {\it Does the science case place any constraints on the @@ -292,5 +296,7 @@ \subsection{Conclusions} \end{description} +% LSST Review from Niel Brandt: survey must span full 10 years to enable good astrometry / propoer motion measurements to aid in selection. PJM: doesn't fit in the 10 questions, but leaving a note here for the future! + \navigationbar diff --git a/whitepaper/AGN/AGN_Disk_Extrinsic.tex b/whitepaper/AGN/AGN_Disk_Extrinsic.tex index c12dac5..7729f31 100644 --- a/whitepaper/AGN/AGN_Disk_Extrinsic.tex +++ b/whitepaper/AGN/AGN_Disk_Extrinsic.tex @@ -84,7 +84,7 @@ \subsection{Target measurements and discoveries} low-level microlensing that will far exceed previous efforts. Note, however, that the larger the apparent magnification, the more stringent are -the constraints on the geometric information that can be obtained about the source. +the constraints on the geometric properties of the source. \citet{MosqueraandKochanek2011} studied the expected microlensing timescales for all known lensed quasars at the time. They found that the median Einstein crossing time scales, which can statistically be interpreted as the @@ -99,7 +99,7 @@ \subsection{Target measurements and discoveries} that, statistically, in every system, one (for doubles) or two (for quads) high magnification events should be observed in 10~yr of LSST monitoring. -Strong lensing events are also our best chance investigate anomalies in accretion +Strong lensing events also provide our best chance of investigating anomalies in accretion disk geometries. For example, warps due to multiple accretion events or magnetic fields, fragmentation due to gravitational instability, and hot spots due to embedded star formation can all result in deviations from smooth temperature profiles. @@ -219,7 +219,7 @@ \subsection{Metrics} \item ��Macro'' lens model parameters on top of lensed quasar images: Surface mass density $\kappa$ and shear $\gamma$. \end{itemize} -\noindent In its current state, the tool assumes simple face-on concentric Gaussian emission regions for the accretion disk. An example of such a curve is shown in figure \ref{microsimcurve}. To recover the figure of merit, (measurement accuracy of $\alpha$ and $\sigma_0$), light curves generated with this tool for a given realistic lensed quasar system ($\kappa$, $\gamma$, s and velocity dispersion of the lensing galaxy as well as time delays between lensed images) for every region in the sky need to analyzed using the above mentioned statistical analyses to recover the input accretion disk parameters. +\noindent In its current state, the tool assumes simple face-on concentric Gaussian emission regions for the accretion disk. An example of such a curve is shown in figure \ref{microsimcurve}. To recover the figure of merit, (measurement accuracy of $\alpha$ and $\sigma_0$), light curves generated with this tool for a given realistic lensed quasar system ($\kappa$, $\gamma$, $s$ and velocity dispersion of the lensing galaxy as well as time delays between lensed images) for every region in the sky need to analyzed using the above mentioned statistical analyses to recover the input accretion disk parameters. % microlensing - convolve microlensing timescales for QSOs we already know @@ -280,7 +280,7 @@ \subsection{Conclusions} \item[Q1:] {\it Does the science case place any constraints on the tradeoff between the sky coverage and coadded depth? For example, should the sky coverage be maximized (to $\sim$30,000 deg$^2$, as e.g., in -Pan-STARRS) or the number of detected galaxies (the current baseline +Pan-STARRS) or the number of detected galaxies (the current baseline of 18,000 deg$^2$)?} \item[A1:] Given that lensed quasars are rare, maximizing the area diff --git a/whitepaper/AGN/AGN_Disk_Intrinsic.tex b/whitepaper/AGN/AGN_Disk_Intrinsic.tex index 5c48e6e..090020c 100644 --- a/whitepaper/AGN/AGN_Disk_Intrinsic.tex +++ b/whitepaper/AGN/AGN_Disk_Intrinsic.tex @@ -30,7 +30,9 @@ \section{Disc Intrinsic AGN Variability}\label{sec:AGNContinuum} LSST band to the continuum flux in another, will be one of the main themes of AGN science in the LSST era (e.g., \citealt{Chelouche2013}; \citealt{CheloucheandZucker2013}; \citealt{EdelsonEtal2015}; -\citealt{FausnaughEtal2015}). Such measurements can test accretion disk models +\citealt{FausnaughEtal2015}). +% LSST Review by Niel Brandt: Add Jiang et al? Sentences below are vague: what can be learned _specifically_ about accretion disk models? +Such measurements can test accretion disk models in a robust manner for a considerably larger number of AGNs than is currently feasible with microlensing (see section~\ref{sec:agn:microlensing}). @@ -119,20 +121,24 @@ \subsection{Target measurements and discoveries} periodic AGNs. Correlation analyses will search for relations between AGN variability properties and their basic physical parameters. In the DDFs, such analyses will enable probing deeper and more frequently, resulting in -higher-quality data that will provide stronger constraints; the only drawback is +higher-quality data that will provide stronger constraints on AGN variability propertie; the only drawback is the relatively smaller number of sources available at the high-luminosity end. A key measurement enabled by the DDFs is a high-quality PSD, in six bands, for the largest number of AGNs to date. These PSDs, which are rich -in diagnostic power, will be used to search for `features' such as QPOs +in diagnostic power, will be used to search for ``features'' such as QPOs and breaks, as well as power-law slopes, that can help constrain SMBH masses -and accretion rates. Additionally, the PSDs can serve as selection +and accretion rates. +% LSST Review from Niel Brandt: describe current optical/NIR PSD results, add refs. +Additionally, the PSDs can serve as selection tools, to more effectively distinguish AGNs from variable stars, as well as a basis to propose cadence perturbations to further enhance AGN selection. -A high-quality PSD, extending to high frequencies (reaching $\sim 1$ min -timescales for stacked PSDs), can effectively distinguish AGNs from other +A high-quality PSD, extending to high frequencies +% (reaching $\sim 1$ min timescales for stacked PSDs), +% PJM: commented out followin LSST Review by Niel Brandt: is 1 min really needed? +can effectively distinguish AGNs from other variable sources, assuming AGN light curves are described by a particular continuous-time autoregressive moving average model (C-ARMA; \citet{KellyEtal14}), i.e., C-ARMA(2,1), corresponding to a damped harmonic oscillator. @@ -249,10 +255,12 @@ \subsection{Metrics} %with the nominal OpSim, and point out potential perturbations in the %cadence to improve the number and quality of such time delays. -While additional work is required for determining the optimal cadence in order -to fully capture AGN accretion physics and to enhance AGN selection, it is clear -that even the nominal DDF sampling (\eg in \opsimdbname{enigma\_1189}) is barely sufficient, and -more frequent sampling would have been ideal. The ability to detect HFQPOs +While additional quantitative work is required for determining the optimal cadence for +fully capturing AGN accretion physics and to enhance AGN selection, it is clear +that even the nominal DDF sampling (\eg in \opsimdbname{db:baseCadence}) is barely sufficient, and +more frequent sampling would be ideal. +% LSST Review from Niel Brandt: Haven't connected the hyperparameters to science impacts clearly. What exactly is lost going from 1 day to 3 day cadence? +The ability to detect HFQPOs should also improve by increasing the sampling frequency, the amplitudes of such features are quite uncertain, as are the (short) duty cycles. Observations, theory and numerical simulations have only suggested that the fractional @@ -269,7 +277,7 @@ \subsection{Metrics} sources with $L \ltsim 10^{42}$~erg~s$^{-1}$, in the DDFs. Such sources are likely to be missed by traditional color-variability selection algorithms due to a strong host contribution. The metric to be developed should assess how the -number of selected LLAGN depends on the sampling frequency in each band. +number of selected LLAGN depends on the sampling frequency in each band, and take into account the host galaxy light contamination. 2) Assessing the standard deviation of the error in recovered time-lag between bands, $\tau$, using a cross-correlation analysis. The goal is to minimize @@ -304,13 +312,14 @@ \subsection{Discussion} % made to improve this science project's figure of merit, and mitigate % the identified risks? -Overall, the key requirement is to increase the nominal sampling +While science-driven metric analysis is still to be performed, we expect the key requirement emerging from such an analysis to be to increase the nominal sampling frequency in the DDFs by at least a factor of 3, i.e., having at least 3000 visits, per band, during the entire survey. Alternatively, if this sampling is not feasible for all the DDFs, it would be beneficial to identify a subset of ``special'' DDFs which would be sampled by this -frequency. Such DDFs would also benefit from being circumpolar, e.g., -the Magellanic Clouds, enabling a more uniform sampling to produce the +frequency. Such DDFs would also benefit from being circumpolar, +% e.g., the Magellanic Clouds, +enabling a more uniform sampling to produce the highest quality PSDs. % ==================================================================== diff --git a/whitepaper/agn.tex b/whitepaper/agn.tex index cdfefe7..2c7cb8c 100644 --- a/whitepaper/agn.tex +++ b/whitepaper/agn.tex @@ -19,15 +19,16 @@ \section*{Summary} \addcontentsline{toc}{section}{~~~~~~~~~Summary} -To zeroth order, AGN science with LSST will benefit from the most -uniform cadence in terms of even sampling for each band and uniform sky +To zeroth order, AGN science with LSST will benefit from the +longest temporal baseline (to aid both selection and variability studies), the most +uniform cadence in terms of even sampling for each band, and uniform sky coverage while maximizing the area, but excluding the Galactic plane. It is also expected that any reasonable perturbation to the nominal LSST observing strategy will not have a major effect on AGN science. While denser sampling at shorter wavelengths will aid investigations of the size and structure of the AGN central engine via intrinsic continuum variability and microlensing, care must be taken not to compromise the -coadded $Y$-band depth which is crucial for detecting the most distant +coadded $Y$-band depth which is crucial for detecting the distant-most quasars. Assuming two visits per night, two different bands are preferred. Science cases related to intrinsic continuum and broad-emission line variability will benefit from the denser sampling