Sasmirala Individual Information for NGC 1386

Description

NGC 1386 is an edge-on spiral galaxy in the Fornax cluster at a distance of D = 16.5 ± 0.8 Mpc (NED redshift independent median) with a Sy 2 nucleus with broad lines in the near-infrared [reunanen_near-infrared_2002] that belongs to the nine-month BAT AGN sample. The nuclear radio source is slightly extended to the south (PA~ 170^∘; [nagar_radio_1999]), and is surrounded by a biconical north-south extended NLR, which has been extensively studied (major axis~ 6arcsec ~ 480 pc; PA~ 5^∘; e.g., [weaver_kinematics_1991, ferruit_hubble_2000, schmitt_hubble_2003, bennert_size_2006-1]). In addition, a nuclear H₂O mega-maser was detected [braatz_survey_1996, braatz_survey_1997]. The first MIR observations of NGC 1386 were performed by [phillips_infrared_1980], followed by [sparks_infrared_1986] and [devereux_spatial_1987]. Later, NGC 1386 was also observed with ISO [clavel_2.5-11_2000, ramos_almeida_mid-infrared_2007] and ESO 3.6 m/TIMMI2 [siebenmorgen_mid-infrared_2004]. The MIR nucleus appeared slightly resolved in the TIMMI2 image. The Spitzer/IRAC, IRS and MIPS images, the MIR nucleus appears nearly unresolved except in the IRAC 8.0 μm image, where the nucleus is slightly elongated along the north-south direction. In addition, faint spiral-like host emission is visible in the IRAC images. Our IRAC 5.8 and 8.0 μm nuclear photometry is ~ 25% lower than the values by [gallimore_infrared_2010] but in rough agreement with the Spitzer/IRS LR staring mode spectrum, while the MIPS 24 μm agrees with the value by [temi_spitzer_2009]. The IRS spectrum is dominated by the deep silicate 10 μm and a moderate silicate 18 μm absorption features in addition to PAH emission, prominent forbidden emission lines and a shallow spectral slope in νF_ν-space (see also [shi_9.7_2006, wu_spitzer/irs_2009, deo_mid-infrared_2009, tommasin_spitzer-irs_2010, gallimore_infrared_2010]). NGC 1386 was imaged with T-ReCS in the broad N and Q filters in 2003 [ramos_almeida_infrared_2009], and an LR N-band spectrum was presented in [gonzalez-martin_dust_2013]. and with VISIR in PAH2_2 and Q2 in 2006 [reunanen_vlt_2010] as well as in PAH1 and SIV_2 in 2010 (this work). In all but the latest two VISIR images, a ~ 1arcsec (80 pc) north-south extended nucleus is visible (PA~ 0^∘). The reason why this extended feature is not visible in the PAH1 and SIV_2 images is presumably the bad MIR seeing during these observations. On the other hand, it is possible that it is intrinsically weaker at shorter wavelengths. The extended emission is aligned with the NLR and thus presumably originates from hot optically thin dust in the NLR as already suggested by [bennert_size_2006-1]. We perform manual PSF-scaling to determine only the unresolved nuclear flux in the VISIR images and obtain values consistent with [reunanen_vlt_2010], while no matching standard star could be retrieved for the T-ReCS images. Therefore, we treat the T-ReCS measurements as upper limits. The resulting VISIR nuclear photometry is on average ~ 50% lower than the Spitzer spectrophotometry and agrees with the T-ReCS spectrum, which exhibits the same silicate 10μm absorption but no PAH emission compared to the IRS spectrum. Therefore, we use the T-ReCS spectrum to estimate the nuclear 12 μm continuum emission corrected for the silicate feature. The subarcsecond-resolution Q-band in relation to the N-band values indicate that the silicate 18 μm absorption has at least the same strength as in the IRS spectrum at subarcsecond resolution. We conclude that the nuclear obscuring structure contributes less than half of the MIR emission in the central 300 pc of NGC 1386, while the other part is caused by a dusty NLR and star formation.

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• [deo_mid-infrared_2009] Rajesh P. Deo, Gordon T. Richards, D. M. Crenshaw, and S. B. Kraemer. The mid-infrared continua of seyfert galaxies . ApJ , 705 pp. 14–31, November 2009.
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• [tommasin_spitzer-irs_2010] Silvia Tommasin, Luigi Spinoglio, Matthew A. Malkan, and Giovanni Fazio. Spitzer-IRS high-resolution spectroscopy of the 12 μm seyfert galaxies. II. results for the complete data set . ApJ , 709 pp. 1257–1283, February 2010.
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• [wu_spitzer/irs_2009] Yanling Wu, Vassilis Charmandaris, Jiasheng Huang, Luigi Spinoglio, and Silvia Tommasin. Spitzer/IRS 5-35 μm low-resolution spectroscopy of the 12 μm seyfert sample . ApJ , 701 pp. 658–676, August 2009.

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.