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Reverberation of high-redshift quasars and its application to trace the dark energy
Copernicus Astronomical Center, Warsaw in collaboration with
M. Bilicki, M. Chodorowski, K. Hryniewicz, M. Krupa, J. Modzelewska, F. Petrogalli, A. Pollo, W. Pych, A. Swieton, A. Udalski, W. Yuan

Boena Czerny

Cambridge, April 2014


Outline


Dark energy issue and the need for independent measurement methods Outline of the quasar-based method Key technical issue: measurement of the time delay of two lightcurves




Dark energy issue
Recent results from Planck: These 4.9 % of barionic matter consists of:

Stars - 0.5 % Gas - 4.1 % Neutrinos - 0.3 %

We need more independent tests to believe!


Current methods of dark energy measurements
Universe content


Universe expansion rate

Standard candle: Supernovae Ia Standard ruler: Cosmic Microwave Background, Large Scale Structure including Barion Acoustic Oscillations,


Measuring the expansion of the Universe with a single object
velocity

distance Hubble diagram


Measuring the expansion of the Universe with a single object

distance

redshift

Original Hubble paper


Measuring the expansion of the Universe with a single object
Luminosity distance

velocity

distance Hubble diagram

redshift Usual diagram for SN Ia


Luminosity distance
L_intr 1/2 D_L = --------------4 pi F_obs So the problem reduces to determination of the absolute liminosity NOT from the redshift but independently In SN Ia this happens since SN Ia are 'standard https://www.llnl.gov/str/SepOct08/hoffman.htm candles'
l

Now we have to do 'the same' for quasars


Absolute luminosity.I.
Hryniewicz PhD Thesis 2013


Absolute luminosity.II.
Theory outlined in Czerny & Hryniewicz (2011): Large outflow forms in the region where the disk temperature is below 1000 K and allows for dust formation Ouflow is cased by radiation pressure acting on dust grains Far from the disk the dusty clouds are irradiated and dust evaporates Dustless material looses support against gravity and falls back Failed wind forms


Absolute luminosity.III.


Spectroscopic studies of time delay of line vs. continuum

Technical problem: We have two lightcurves: continuum luminosity line luminosity Line curve is delayed but results from complex repro cessing with unknown transfer function Goal: measuring time delay


Spectroscopic studies of time delay of line vs. continuum
Past reverberation studies: Our SALT current campaign: Three z = 1 quasars
- about 40 nearby AGN - about 10 z < 0.4 quasars - 7 distant objects but only 1 detection


SALT setup: simulations


Expected delay: 500 ­ 600 days Five spectroscopic observations a year, with over 3 months gap for source observability Denser photometric monitoring
Artificial lightcurves: - red noise power law for continuum - delayed continuum convolved with a Gaussian for a line - both include poissionian measurement errors Czerny et al. 2013




Tested methods for SALT setup


Interpolated CCF Z-transformed DCF Chi2 fitting In simulations the best results were obtained for chi2 fitting, somewhat worse for ZDCF, and poor for ICCF.


Methods untested for our setup: modeling stochastic lightcurve in time domain:


CAR - continuous autoregressive process (Kelly et al. 2009), appropriate for sources with the power spectrum (i) creation of the 'smoothed' stochastic lightcurve at the observational points (removes 'accidental' flares ?) (ii) the same method but used to fill the observational gaps and/or create denser lightcurve (Zu et al. 2011, Grier et al. 2012)






Methods untested for our setup: modeling stochastic lightcurve in time domain:


(iii) methods more advanced than CAR ** Kozlowski et al. 2010 ­ higher order generalization of CAR ** Graham et al. (2014) ­ Slepian wavelet variance

Can they be effectively used to determine better the time delay from poor lightcurves?


Spectroscopic studies: alternative to SALT
Advantages and disadvantages: A few thousands of quasars in comparison with three in SALT Much lower accuracy; 6 ­ 10 percent error in line measurement in comparison with 1 percent in SALT

SALT current campaign: Three z = 1 quasars

LAMOST spectroscopic survey telescope in China


Pure photometric multi-chanel studies
We also simulate now the possibilities to use the future LSST (Large Synoptic Sky Survey). Preliminary estimates of the line contribution to the photometric chanels.


Observational setups for LAMOST and LSST


LAMOST - ten spectrophotometric observations of an object per year, large errors (up to 10 per cent), thousands of objects LSST - up to 100 observations per year of an objects, line and continuum combined, hundreds of thousands of objects
WHICH METHOD WILL BE MORE EFFECTIVE IN THESE TWO CASES?




First quasar with tentatively measured delay from HET
Quasar S5 0836+7
HET 7 yr monitoring Kaspi et al. (2007) tau_rest = 595 days z = 2.172

Delta mu = + 0.39
Our source CTS C30.10: tau_rest 260 days (?)

Figure from Betoule et al. 2014

z = 0.9 Delta mu =

+0.28