1 / 21

Photometric Reverberation Mapping of NGC 4395

Photometric Reverberation Mapping of NGC 4395. The Restless Nature of AGNs 22 May , 2013. Stephen Rafter – The Technion , Haifa Israel. Collaborators. Haim Edri – Masters Student - the Technion Doron Chelouche – Tel Aviv University/Univ. of Haifa

azia
Télécharger la présentation

Photometric Reverberation Mapping of NGC 4395

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Photometric Reverberation Mapping of NGC 4395 The Restless Nature of AGNs 22 May, 2013 Stephen Rafter – The Technion, Haifa Israel

  2. Collaborators • HaimEdri – Masters Student - the Technion • DoronChelouche – Tel Aviv University/Univ. of Haifa • ShaiKaspi – Tel Aviv University/the Technion • Ehud Behar – the Technion

  3. Broad Band Photometric RM • Use broad band filters to detect time lags between continuum and emission lines when their signal is mixed in a given band NGC 4395 & SDSS filters

  4. The Photometric RM Method • We follow the method developed by Chelouche & Daniel (2012) as follows: Take 2 filters, one which covers a ‘continuum only’ region, and a second which covers a region with lines and continuum such that we can define light curves for filters X and Y such that (1) FX (t) = fXc(t) (2) FY (t) = fYc(t) + fYl(t)

  5. The Photometric RM Method • The CCF between the lines and continuum is given by: (3) CCFlc(τ) = fYl(t +τ) * fYc(t) (4) CCFlc(τ) = [FY(t + τ) - fYc(t +τ)] * fYc(t) • Since the continuum is the dominant variable source contributing to the band (> 80%) we assume: (5) fYc(t) ≈ FX (t) (6) CCFlc(τ) = [FY(t + τ) - FX(t +τ)] * FX(t) (7) CCFlc(τ) = CCFXY(τ) - ACFX(τ)

  6. Simulations • Generate a ‘continuum’ light curve (LC) • Shift by hand in time (τ) and scale down amplitude of variabilityto simulate line response to continuum variations • Add the line and continuum LCs FX (t) FY (t)

  7. Simulations • Compute the CCF and ACF and look for a peak in the difference. We recover the input time lag of ~4 hours Units in the lower panel have no ‘physical’ significance

  8. Simulations • Flux randomization (FR) within measured error bars in a Monte Carlo simulation (also random subsets, RSS) • Final measurement is τ = 3.8 +1.5 hours -1.1

  9. Why NGC 4395? • Nearby, so it’s bright and well studied • DL ≈ 5 Mpc • g` ≈ 14.5 mag • Lowest luminosity of any confirmed AGN: • Lbol = 7 x 1039 erg s-1 • Low luminosity implies RBLR on the order of a few hours • HST CIV RM gives • RBLR≈ 1 hour (Peterson et al. 2005)

  10. Photometric Observations and LCs • 9 nights using the Wise Observatory's 1 meter telescope • SDSS g', r' and i' broad band filters, 5 minute exposure

  11. NGC 4395 – g` & r` Bands • The g` band is ‘continuum’ • τ = 3.68 +0.70 hours -0.84

  12. NGC 4395 – i` & r` Bands • The i` band is continuum • τ = 3.46 +1.59 hours -0.36

  13. NGC 4395 Velocity • Hβ is fit atypically here with 3 components: Narrow ~ 65 km/s (modeled using [OIII] lines) Intermediate ~ 250 km/s (put in by hand) Broad ~ 1500 km/s (free parameter) Hi-Res Keck Spectrum 2011 from Ari Laor

  14. Mass Estimation • To calculate the mass we take: • ΔV = 1500 ± 500 km/s • τ = 3.6 ± 0.8 hours • f = 0.75 (isotropic circular velocity field) MBH = 1.464 x 105 (RBLR/days) (ΔV/1000 km s-1)2 MBH = 4.9 ± 2.6 x 104 M Based on this study NGC 4395 is about here

  15. Comparing to Previous Work

  16. The Next Step:The Multivariate Correlation Function • An extension of the CCF-ACF method outlined in Chelouche & Zucker (2013, accepted by ApJ.) • Adds an extra parameter, α, which is the fractional line contribution to the total flux in the band where: • α = 1 is a pure line emission light curve • α = 0 is a pure continuum light curve • Alleviates the need for spectral decomposition to obtain a pure continuum light curve, which can be subjective due to broad line wings and line blends in spectroscopic RM.

  17. SDSS NLS1 Candidate “SL01” & The Multivariate Correlation Function

  18. MCF Time Lag for Hα Maximum at τ = 18+3 days and α = 0.12 -7 Warmer colors represent a higher correlation coefficient

  19. Comparison of Methods ICCF and ZDCF determined spectroscopically

  20. Comparing RM Methods Broad Band Photometric Reverberation

  21. Conclusions • We use broad band filters and the CCF – ACF difference method to estimate RBLR for NGC 4395 (see Edri et al. 2012 for formal results) • We introduce the MCF method which adds an addition parameter to characterize the contribution of variable line emission to a broad band light curves • The MCF method can be applied to moderate/low resolution spectra to determine time lags as well as broad band light curves • These methods can be applied to large area time series surveys like LSST to estimate RBLR for a very large number of AGN • Still a lot of work to do and there will be more results to follow…

More Related