Person: Huchra, John
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Huchra
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Huchra, John
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Publication Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. III - Further observations of NGC 5548 at optical wavelengths(IOP Publishing, 1992) Peterson, B. M.; Alloin, D.; Axon, D.; Balonek, T. J.; Bertram, R.; Boroson, T. A.; Christensen, J. A.; Clements, S. D.; Dietrich, M.; Elvis, Martin; Filippenko, A. V.; Gaskell, C. M.; Haswell, C. A.; Huchra, John; Jackson, N.; Kollatschny, W.; Korista, K. T.; Lame, N. J.; Leacock, R. J.; Lin, S.-N.; Malkan, M. A.; Monk, A. S.; Penston, M. V.; Pogge, R. W.; Robinson, A.; Rosenblatt, E. I.; Shields, J. C.; Smith, A. G.; Stirpe, G. M.; Sun, W.-H.; Turner, T. J.; Wagner, R. M.; Wilkes, Belinda; Wills, B. J.The results of the second year of an intensive ground-based spectroscopic and photometric study of variability in the bright Seyfert 1 galaxy NGC 5548 are reported in order to study the relationship between continuum and emission-line variability. Relative to the first year of the monitoring program, the nucleus of NGC 5548 was considerably fainter and the continuum variations slower during the second year, but the continuum H-beta cross-correlation results for the two years are nearly identical. The variations in the broad H-beta emission-line lag behind those in the continuum by somewhat less than 20 days, as concluded from the first year's data.Publication Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. II - an intensive study of NGC 5548 at optical wavelengths(IOP Publishing, 1991) Peterson, B. M.; Balonek, T. J.; Barker, E. S.; Bechtold, J.; Bertram, R.; Bochkarev, N. G.; Bolte, M. J.; Bond, D.; Boroson, T. A.; Carini, M. T.; Carone, T. E.; Christensen, J. A.; Clements, S. D.; Cochran, A. L.; Cohen, R. D.; Crampton, D.; Dietrich, M.; Elvis, Martin; Ferguson, A.; Filippenko, A. V.; Fricke, K. J.; Gaskell, C. M.; Halpern, J. P.; Huchra, John; Hutchings, J. B.; Kollatschny, W.; Koratkar, A. P.; Korista, K. T.; Krolik, J. H.; Lame, N. J.; Laor, A.; Leacock, R. J.; MacAlpine, G. M.; Malkan, M. A.; Maoz, D.; Miller, H. R.; Morris, S. L.; Netzer, H.; Oliveira, C. L. M.; Penfold, J.; Penston, M. V.; Perez, E.; Pogge, R. W.; Richmond, M. W.; Romanishin, W.; Rosenblatt, E. I.; Saddlemyer, L.; Sadun, A.; Sawyer, S. R.; Shields, J. C.; Shapovalova, A. I.; Smith, A. G.; Smith, H. A.; Smith, P. S.; Sun, W.-H.; Thiele, U.; Turner, T. J.; Veilleux, S.; Wagner, R. M.; Weymann, R. J.; Wilkes, Belinda; Wills, B. J.; Wills, D.; Younger, P. F.A large, international program of ground-based optical spectroscopy and photometry of the variable Seyfert 1 galaxy NGC 5548 undertaken in support of an IUE monitoring campaign is described. This contribution presents the data base and describes the methods used to correct for systematic differences between spectra from different sources. Optical continuum and H-beta emission-line light curves are derived from the spectra. The behavior of the optical continuum is qualitatively the same as the behavior of the ultraviolet continuum. Cross-correlation of the ultraviolet and optical continuum measurements does not reveal any significant lag between them. The h-beta emission-line variations show the same basic pattern as seen in the continuum and ultraviolet emission lines, with H-beta lagging behind the continuum by about 20 days. This is significantly larger than the about 10 day lag deduced for Ly-alpha.Publication Optical Continuum and Emission‐Line Variability of the Seyfert 1 Galaxy Markarian 509(IOP Publishing, 1996) Carone, T. E.; Peterson, B. M.; Bechtold, J.; Bertram, R.; Bischoff, K.; Dietrich, M.; Filppenko, A. V.; Ho, L. C.; Huchra, John; Kollatchny, W.; Korista, K. T.; Matheson, T.; Pogge, R. W.; Shields, J. C.; Smith, P. S.; Wagner, R. M.; Wilkes, BelindaWe report on the results of a 5 year coordinated program of spectroscopic monitoring of the luminous Seyfert 1 galaxy Markarian 509. The Hβ and He II λ4686 emission lines are found to respond to continuum variations with time lags of ~80 and ~60 days, respectively, considerably longer than the emission-line lags measured for other Seyfert galaxies.Publication Narrow-line AGN in the ISO-2MASS survey(EDP Sciences, 2007) Leipski, C.; Haas, M.; Meusinger, H.; Siebenmorgen, R.; Chini, R.; Drass, H.; Albrecht, M.; Wilkes, Belinda; Huchra, John; Ott, S.; Cesarsky, C.; Cutri, R.Context. A long-standing challenge of observational AGN research is to find type 2 quasars, the luminous analogues of Seyfert-2 galaxies. Aims. We search for luminous narrow-line type 2 AGN, characterise their properties, and compare them with broad-line type 1 AGN. Methods. Combining the ISOCAM parallel survey at 6.7 $\mu$m with 2MASS, we have selected AGN via near-mid-infrared colours caused by the hot nuclear dust emission. We performed spectroscopy in the optical and, for a subset of the sample, also in the mid-infrared with Spitzer. Results. We find nine type 2 AGN at redshift 0.10.5 we did not find type 2 AGN, probably because the hottest dust emission, still covered by the NIR filters, is obscured. The optical spectra of the type 2 host galaxies show young and old stellar populations. Only one object is an ultraluminous infrared galaxy with starburst. The 5-38 $\mu$m spectra of the two type 2 sources observed show a strong continuum with PAH emission in one case and silicate absorption in the other case. Conclusions. The near-mid-infrared selection is a successful strategy to find luminous type 2 AGN at low z. The objects exhibit a large range of properties so that it is difficult to infer details by means of popular SED fitting with simple average templates.Publication Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. IV - Intensity variations of the optical emission lines of NGC 5548(IOP Publishing, 1993) Dietrich, M.; Kollatschny, W.; Peterson, B. M.; Bechtold, J.; Bertram, R.; Bochkarev, N. G.; Boroson, T. A.; Carone, T. E.; Elvis, Martin; Filippenko, A. V.; Gaskell, C. M.; Huchra, John; Hutchings, J. B.; Koratkar, A. P.; Korista, K. T.; Lame, N. J.; Laor, A.; MacAlpine, G. M.; Malkan, M. A.; Mendes de Oliveira, C.; Netzer, H.; Penfold, J.; Penston, M. V.; Perez, E.; Pogge, R. W.; Richmond, M. W.; Rosenblatt, E. I.; Shapovalova, A. I.; Shields, J. C.; Smith, H. A.; Smith, P. S.; Sun, W.-H.; Thiele, U.; Veilleux, S.; Wagner, R. M.; Wilkes, Belinda; Wills, B. J.; Wills, D.Measurements of optical emission-line flux variations based on spectra of the Seyfert galaxy NGC 5548 obtained between December 1988 and October 1989 are reported. All of the measured optical emission lines, H-alpha, H-beta, H-gamma, He I 5876, and He II 4686, exhibit the same qualitative behavior as the UV and optical continua, but with short time delays, or lags, which are different for the various lines. Cross-correlation analysis is applied to measure the lags between the various lines and the continuum. Similar lags are found with respect to the UV continuum for H-alpha and H-beta, 17 and 19 d, respectively. The lag for H-gamma is shorter (13 d), only somewhat larger than the lag measured for Ly-alpha (about 10 d). The helium lines respond to continuum variations more rapidly than the hydrogen lines, with lags of about 7 d for He II 4686 and 11 d for He I 5876.Publication Steps toward Determination of the Size and Structure of the Broad‐Line Region in Active Galactic Nuclei. XV. Long‐Term Optical Monitoring of NGC 5548(IOP Publishing, 1999) Peterson, B. M.; Barth, A. J.; Berlind, P.; Bertram, R.; Bischoff, K.; Bochkarev, N. G.; Burenkov, A. N.; Cheng, F.‐Z.; Dietrich, M.; Filippenko, A. V.; Giannuzzo, E.; Ho, L. C.; Huchra, John; Hunley, J.; Kaspi, S.; Kollatschny, W.; Leonard, D. C.; Malkov, Yu. F.; Matheson, T.; Mignoli, M.; Nelson, B.; Papaderos, P.; Peters, J.; Pogge, R. W.; Pronik, V. I.; Sergeev, S. G.; Sergeeva, E. A.; Shapovalova, A. I.; Stirpe, G. M.; Tokarz, S.; Wagner, R. M.; Wanders, I.; Wei, J.‐Y.; Wilkes, Belinda; Wu, H.; Xue, S.‐J.; Zou, Z.‐L.We present the results of 3 yr of ground-based observations of the Seyfert 1 galaxy NGC 5548, which, combined with previously reported data, yield optical continuum and broad-line Hβ light curves for a total of 8 yr. The light curves consist of over 800 points, with a typical spacing of a few days between observations. During this 8 yr period, the nuclear continuum has varied by more than a factor of 7, and the Hβ emission line has varied by a factor of nearly 6. The Hβ emission line responds to continuum variations with a time delay or lag of ~10-20 days, the precise value varying somewhat from year to year. We find some indications that the lag varies with continuum flux in the sense that the lag is larger when the source is brighter.Publication Multiwavelength Observations of Short-Timescale Variability in NGC 4151. IV. Analysis of Multiwavelength Continuum Variability(IOP Publishing, 1996) Edelson, R. A.; Alexander, T.; Crenshaw, D. M.; Kaspi, S.; Malkan, M. A.; Peterson, B. M.; Warwick, R. S.; Clavel, J.; Filippenko, A. V.; Horne, K.; Korista, K. T.; Kriss, G. A.; Krolik, J. H.; Maoz, D.; Nandra, K.; O, P. T.; Penton, S. V.; Yaqoob, T.; Albrecht, P.; Alloin, D.; Ayres, T. R.; Balonek, T. J.; Barr, P.; Barth, A. J.; Bertram, R.; Bromage, G. E.; Carini, M.; Carone, T. E.; Cheng, F.-Z.; Chuvaev, K. K.; Dietrich, M.; Dultzin-Hacyan, D.; Gaskell, C. M.; Glass, I. S.; Goad, M. R.; Hemar, S.; Ho, L. C.; Huchra, John; Hutchings, J.; Johnson, W. N.; Kazanas, D.; Kollatschny, W.; Koratkar, A. P.; Kovo, O.; Laor, A.; MacAlpine, G. M.; Magdziarz, P.; Martin, P. G.; Matheson, T.; McCollum, B.; Miller, H. R.; Morris, S. L.; Oknyanskij, V. L.; Penfold, J.; Perez, E.; Perola, G. C.; Pike, G.; Pogge, R. W.; Ptak, R. L.; Qian, B.-C.; Recondo-Gonzalez, M. C.; Reichert, G. A.; Rodriguez-Espinoza, J. M.; Rodriguez-Pascual, P. M.; Rokaki, E. L.; Roland, J.; Sadun, A. C.; Salamanca, I.; Santos-Lleo, M.; Shields, J. C.; Shull, J. M.; Smith, D. A.; Smith, S. M.; Snijders, M. A. J.; Stirpe, G. M.; Stoner, R. E.; Sun, W.-H.; Ulrich, M.-H.; van Groningen, E.; Wagner, R. M.; Wagner, S.; Wanders, I.; Welsh, W. F.; Weymann, R. J.; Wilkes, Belinda; Wu, H.; Wurster, J.; Xue, S.-J.; Zdziarski, A. A.; Zheng, W.; Zou, Z.-L.This paper combines data from the three preceding papers in order to analyze the multi-wave-band variability and spectral energy distribution of the Seyfert I galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths; The strongest variatIons were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA = 6%) variations (uncorrelated with those at lower energies) were seen at soft gamma ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 A. These data do not probe extreme ultraviolet (1200 A to 0.1 keV) or hard X ray (2-50 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of <~ 0.15 day between 1275 A and the other ultraviolet bands, <~0.3 day between 1275 A and 1.5 keV, and <~1 day between 1275 and 512 A. These tight limits represent more than an order of magnitude improvement over those determined in previous multi wave band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (a <= -2.5). If photons emitted at a "primary" wave band are absorbed by nearby material and "reprocessed" to produce emission at a secondary wave band, causality arguments require that variations in the secondary band follow those in the primary band. The tight interband correlation and limits on the ultraviolet and medium-energy X-ray lags indicate that the reprocessing region is smaller than ~0.15 lt-day in size. After correcting for strong (a factor of ~> 15) line-of-sight absorption, the medium-energy X-ray luminosity variations appear adequate to drive the ultraviolet/optical variations. However the medium-energy X-ray NVA is 2- 4 times that in the ultraviolet, and the single-epoch absorption- corrected X-ray/gamma ray luminosity is only about one third of that of the ultraviolet optical/infrared, suggesting that at most about a third of the total low energy flux could be reprocessed high-energy emission. The strong wavelength dependence of the ultraviolet NVAs is consistent with an origin in an accretion disk, with the variable emission coming from the hotter inner regions and nonvariable emission from the cooler outer regions. These data, when combined with the results of disk fits indicate a boundary between these regions near a radius of order R ~ 0.07 lt-day. No interband lag would be expected, as reprocessing (and thus propagation between regions) need not occur, and the orbital timescale of 1 day is consistent with the observed variability timescale. However, such a model does not immediately explain the good correlation between ultraviolet and X-ray variations.Publication Steps toward determination of the size and structure of the broad-line region in active nuclei. 7: Variability of the optical spectrum of NGC 5548 over years(IOP Publishing, 1994) Peterson, B. M.; Berlind, Perry; Bertram, R.; Bochkarev, N. G.; Bond, D.; Brotherton, M. S.; Busler, J. R.; Chuvaev, K. K.; Cohen, R. D.; Dietrich, M.; Elvis, Martin; Filippenko, A. V.; Foltz, C. B.; Garnavich, P. M.; Ho, L. C.; Horine, E.; Horne, K.; Huchra, John; Kollatschny, W.; Korista, K. T.; Malkan, M. A.; Matheson, T.; Mignoli, M.; Morris, S. L.; Nazarova, L.; Penfold, J.; Peters, J.; Pogge, R. W.; Pronik, V. I.; Rush, B.; Sergeev, S. G.; Shapovalova, A. I.; Shields, J. C.; Stirpe, G. M.; Tokarz, S.; Wagner, Rudolf; Weymann, R. J.; White, R. J.; Wilkes, Belinda; Wills, D.; Wills, B. J.; Winge, C.; Younger, P. F.We report on the results of a continuation of a large monitoring program of optical spectroscopy of the Seyfert 1 galaxy NGC 5548. The new observations presented here were obtained between 1990 December and 1992 October, and extend the existing database to nearly 1400 days, dating back to 1988 December. The continuum variations are generally smooth and well-resolved, except during the third year of this 4 year project, when the variations were apparently more rapid and of lower amplitude than observed at other times. The broad H(beta) emission line is found to vary in response to the continuum variations with a lag of about 18 days, but with some changes from year to year. The H(beta) transfer functions for each of the 4 yr and for the entire 4 yr database are derived by using a maximum entropy method.Publication A Spectroscopic and Photometric Study of Short-Timescale Variability in NGC 5548(2001) Dietrich, M.; Bender, C.; Bergmann, D.; Bills, T.; Bochkarev, N.; Burenkov, A.; Gaskell, C.; Gutzmer, D.; Grove, R.; Hiller, M.; Huchra, John; Klimek, E.; Lund, C.; Merkulova, N.; Pebley, S.; Poulsen, M.; Pronik, V.; Sergeev, S.; Sergeeva, E.; Shapovalova, A.; Vlasyuk, V.; Wilkes, BelindaResults of a ground-based optical monitoring campaign on NGC 5548 in June 1998 are presented. The broad-band fluxes (U, B, V), and the spectrophotometric optical continuum flux F wavelength (5100 Å) monotonically decreased in flux while the broad-band R and I fluxes and the integrated emission-line fluxes of H alpha and H beta remained constant to within 5% . On June 22, a short continuum flare was detected in the broad band fluxes. It had an amplitude of about ~18% and it lasted only ~ 90 min. The broad band fluxes and the optical continuum F wavelength (5100 Å) appear to vary simultaneously with the EUV variations. No reliable delay was detected for the broad optical emission lines in response to the EUVE variations. Narrow H beta emission features predicted as a signature of an accretion disk were not detected during this campaign. However, there is marginal evidence for a faint feature at wavelength ~ 4962Åwith FWHM ~ 6 Åredshifted by delta v 1100kms-1 km s-1 with respect to H beta (narrow).