Sasmirala Individual Information for NGC 6814

Description

NGC 6814 is a face-on grand-design spiral galaxy at a redshift of z = 0.0052 (D ~ 21.2 Mpc) with a Sy 1.5 nucleus [veron-cetty_catalogue_2010]. This nucleus is variable by one order of magnitude variable in X-rays [koenig_seyfert_1997, mukai_x-ray_2003] and belongs to the nine-month BAT AGN sample. In addition, optical type changes from Sy 1.0 to Sy 1.9 have been reported [sekiguchi_spectral_1990]. It features a slightly resolved radio core with north-south extension of ~ 4arcsec ~ 0.4 kpc and a minor-axis extension of ~ 2arcsec ~200 pc to the west [ulvestad_radio_1984]. Additionally, extended [O III] emission ~ 1arcsec ~ 100 pc along a PA~ 150^∘ has been reported[schmitt_comparison_1996]. Pioneering MIR observations of NGC 6814 were performed by [kleinmann_observations_1970], followed by [rieke_infrared_1972, rieke_infrared_1978] and [glass_mid-infrared_1982]. After IRAS, NGC 6814 was followed up in the MIR with ISO [laurent_mid-infrared_2000] and Spitzer/IRAC, IRS and MIPS. The corresponding IRAC and MIPS images show a dominating compact nucleus embedded within spiral-like host emission. The IRS LR staring-mode spectrum exhibits silicate 10 and 18μm emission, very weak PAH features, and a flat spectral slope in νF_ν-space (see also [pereira-santaella_mid-infrared_2010]). Thus, the arcsecond-scale MIR SED appears to be AGN-dominated with at best minor star-formation contribution. We observed the nuclear region of NGC 6814 with VISIR in four narrow N-band filters in 2007 (partly published in [gandhi_resolving_2009]). In addition, T-ReCS imaging in the Si2 and Qa filters was performed in 2009 [ramos_almeida_testing_2011]. In all cases, a compact nucleus without further host emission was detected. The nucleus is unresolved in the T-ReCS images, while it appears elongated in all the single-epoch VISIR images (PA~ 100^∘). Because the T-ReCS images were taken during better MIR seeing conditions, we classify the nucleus as unresolved. Our nuclear photometry is consistent with the previously published values of the same data and also with the Spitzer spectrophotometry. Therefore, we use the latter to compute the 12 and 18 μm continuum emission estimates corrected for the silicate features. The combination of all available MIR data of NGC 6814 is consistent with no N-band flux variations during the last ~ 40 years, except for the very first measurement by [kleinmann_observations_1970] which might be caused by calibration systematics.

• [gandhi_resolving_2009] P. Gandhi, H. Horst, A. Smette, S. Hönig, A. Comastri, R. Gilli, C. Vignali, and W. Duschl. Resolving the mid-infrared cores of local seyferts . A&A , 502 pp. 457–472, August 2009.
• [glass_mid-infrared_1982] I. S. Glass, A. F. M. Moorwood, and W. Eichendorf. Mid-infrared observations of seyfert 1 and narrow-line x-ray galaxies . A&A , 107 pp. 276–282, March 1982.
• [kleinmann_observations_1970] D. E. Kleinmann and F. J. Low. Observations of infrared galaxies . ApJL , 159 pp. L165, March 1970.
• [koenig_seyfert_1997] M. Koenig, S. Friedrich, R. Staubert, and J. Timmer. The seyfert galaxy NGC 6814 - a highly variable x-ray source. . A&A , 322 pp. 747–750, June 1997.
• [laurent_mid-infrared_2000] O. Laurent, I. F. Mirabel, V. Charmandaris, P. Gallais, S. C. Madden, M. Sauvage, L. Vigroux, and C. Cesarsky. Mid-infrared diagnostics to distinguish AGNs from starbursts . A&A , 359 pp. 887–899, July 2000.
• [mukai_x-ray_2003] K. Mukai, C. Hellier, G. Madejski, J. Patterson, and D. R. Skillman. X-ray variability of the magnetic cataclysmic variable v1432 aquilae and the seyfert galaxy NGC 6814 . ApJ , 597 pp. 479–493, November 2003.
• [pereira-santaella_mid-infrared_2010] Miguel Pereira-Santaella, Aleksandar M. Diamond-Stanic, Almudena Alonso-Herrero, and George H. Rieke. The mid-infrared high-ionization lines from active galactic nuclei and star-forming galaxies . ApJ , 725 pp. 2270–2280, December 2010.
• [ramos_almeida_testing_2011] C. Ramos Almeida, N. A. Levenson, A. Alonso-Herrero, A. Asensio Ramos, J. M. Rodríguez Espinosa, A. M. Pérez García, C. Packham, R. Mason, J. T. Radomski, and T. Díaz-Santos. Testing the unification model for active galactic nuclei in the infrared: Are the obscuring tori of type 1 and 2 seyferts different? . ApJ , 731 pp. 92, April 2011.
• [rieke_infrared_1972] G. H. Rieke and F. J. Low. Infrared photometry of extragalactic sources . ApJL , 176 pp. L95, September 1972.
• [rieke_infrared_1978] G. H. Rieke. The infrared emission of seyfert galaxies . ApJ , 226 pp. 550–558, December 1978.
• [schmitt_comparison_1996] Henrique R. Schmitt and Anne L. Kinney. A comparison between the narrow-line regions of seyfert 1 and seyfert 2 galaxies . ApJ , 463 pp. 498, June 1996.
• [sekiguchi_spectral_1990] K. Sekiguchi and J. W. Menzies. Spectral variations in the broad-line region of NGC 6814 . MNRAS , 245 pp. 66–70, July 1990.
• [ulvestad_radio_1984] J. S. Ulvestad and A. S. Wilson. Radio structures of seyfert galaxies. VI - VLA observations of a nearby sample . ApJ , 285 pp. 439–452, October 1984.
• [veron-cetty_catalogue_2010] M.-P. Véron-Cetty and P. Véron. A catalogue of quasars and active nuclei: 13th edition . A&A , 518 pp. 10, July 2010.

Images

SEDs

MIR SED. The description of the symbols in all the SED plots (where present) is the following: Grey crosses and solid lines mark the Spitzer/IRAC, MIPS and IRS data. The colour coding of the other symbols is as follows: green for COMICS, magenta for Michelle, blue for T-ReCS and red for VISIR data. Darker-coloured solid lines mark spectra of the corresponding instrument. The black filled circles mark the nuclear 12 and 18 micron continuum emission estimate from the data (where present). The ticks on the top axis mark positions of common MIR emission lines, while the light grey horizontal bars mark wavelength ranges affected by the silicate 10 and 18 micron features.