Sasmirala Individual Information for NGC 5995

Description

NGC 5995 is an inclined barred spiral galaxy at a redshift of z = 0.0252 (D ~117 Mpc) with a Sy 1.9 nucleus [veron-cetty_catalogue_2010], which was detected as a compact radio source [thean_high-resolution_2000]. After its detection in IRAS, this object was followed up with Palomar 5 m/MIRLIN [gorjian_10_2004] and ESO 3.6 m/TIMMI2 [galliano_mid-infrared_2005]. An unresolved nucleus at arcsecond resolution was detected in both data sets. The Spitzer/IRAC and MIPS images are also dominated by a compact nucleus without significant host emission. Our corresponding nuclear IRAC 5.8 μm photometry agrees with [gallimore_infrared_2010], while our IRAC 8.0 μm flux is ~ 30% lower than published by these authors. In comparison, our fluxes are consistent with the Spitzer/IRS spectrum. Not surprisingly, our MIPS 24 μm flux is significantly higher than the star-formation subtracted nuclear flux from [shi_unobscured_2010]. The Spitzer/IRS LR mapping-mode spectrum exhibits silicate 10 μm absorption, PAH emission and a flat spectral slope in νFν-space (see also [wu_spitzer/irs_2009, tommasin_spitzer-irs_2010, shi_unobscured_2010, gallimore_infrared_2010]). Thus, the arcsecond-scale MIR SED seems to be affected by star formation. We observed the nuclear region of NGC 5995 with VISIR in three narrow N-band filters in 2006 [horst_mid_2008, horst_mid-infrared_2009] and another two in 2010 (unpublished, to our knowledge), and also obtained a LR N-band spectrum in 2009 [honig_dusty_2010-1]. A compact MIR nucleus was detected in all images, and the diffraction-limited high-S/N images from 2010 show that the nucleus is unresolved, which has not been clear form the 2006 images. Our nuclear photometry is consistent with the previously published values, yet systematically higher by ~ 10% compared to the VISIR spectrum. However, this offset is well within the calibration uncertainties. The corresponding nuclear MIR SED has on average ~ 13% lower flux levels than the arcsecond-scale MIR SED as traced by Spitzer, while exhibiting the same silicate 10 μm absorption and much weaker PAH emission. Therefore, we conclude that the silicate feature is generic to the (projected) central ~ 200 pc of NGC 5995, and star-formation contribution towards the nuclear MIR SED is presumably very low. The nuclear MIR emission of NGC 5995 could be resolved with MIDI interferometric observations and was modelled as two approximately equally bright components, one extending for ~ 20 pc, and the other one remaining unresolved (< 5 pc; [burtscher_diversity_2013]).

Images

Optical image (DSS, red filter). Displayed are the central 4 arcmin with North being up and East to the left. The colour scaling is linear with white corresponding to the median background (BG) and black to the 0.01% pixels with the highest intensity.

Spitzer MIR images. Displayed are the inner 40 arcsec with North being up and East to the left. The colour scaling is logarithmic with white corresponding to median BG and black to the 0.1% pixels with the highest intensity. The label in the bottom left states instrument and central wavelength of the filter in micron (I: IRAC, M: MIPS).

Subarcsecond-resolution MIR images sorted by increasing filter central wavelength. Displayed are the inner 4 arcsec with North being up and East to the left. The colour scaling is logarithmic with white corresponding to median BG and black to the 75% of the highest intensity of all images in units of sig_bg. The inset image (where present; either bottom or top right) shows the central arcsecond of the PSF from the calibrator star, scaled to match the science target. The labels in the bottom left state instrument and filter names (C: COMICS, M: Michelle, T: T-ReCS, V: VISIR).

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.

Photometry details and reduced FITS files

ObjectRA
[deg]
Dec
[deg]
FilterImageInfoλ_c
[um]
HWHM
[um]
InstrPix. size
[arcsec/pix]
T_exp
[s]
ModeChop Throw
[arcsec]
Chop Angle
[deg]
Rot
[deg]
Prog IdCal. StarCal. DateDate Obs.Factor
[mJy/ct]
Err. Factor
[mJy/ct]
Cal. Flux
[mJy]
Upper Lim. Gauss?F_Gauss
[mJy]
E(F_Gauss)
[mJy]
Upper Lim. PSF?F_PSF
[mJy]
E(F_PSF)
[mJy]
Cal. Maj.
[arcsec]
Cal. Min.
[arcsec]
Cal. PA.
[deg]
Maj. Ax
[arcsec]
Min. Ax
[arcsec]
Pos. Ang.
[deg]
NGC 5995237.104167-13.757778NEIINGC5995_NEII_2006-04-14T04-57.fits[Details]12.810.21VISIR0.075179.0PARA8.045.00.0077.B-0137(A)HD1337742006-04-14T05:48:29Z2006-04-14T04:56:38Z0.061720.001687421.1False384.623.1False375.526.50.460.3484.00.440.3691.0
NGC 5995237.104167-13.757778PAH2NGC5995_PAH2_2006-04-14T04-52.fits[Details]11.250.59VISIR0.075181.0PARA8.045.00.0077.B-0137(A)HD1337742006-04-14T05:45:36Z2006-04-14T04:52:19Z0.015520.000359558.7False326.410.1False259.110.20.390.385.00.450.33100.0
NGC 5995237.104167-13.757778PAH2NGC5995_PAH2_2010-07-26T00-19.fits[Details]11.250.59VISIR0.0752175.0PERP8.00.00.0085.B-0251(C)HD1337742010-07-26T00:05:46Z2010-07-26T00:18:43Z0.013620.000469558.7False314.311.0False324.011.60.330.31147.00.330.31154.0
NGC 5995237.104167-13.757778PAH2_2NGC5995_PAH2_2_2010-07-26T00-40.fits[Details]11.880.37VISIR0.0752167.0PERP8.00.00.0085.B-0251(C)HD1337742010-07-26T00:11:31Z2010-07-26T00:40:19Z0.021110.000618247.1False323.59.5False316.311.50.370.33160.00.360.3373.0
NGC 5995237.104167-13.757778SIVNGC5995_SIV_2006-04-14T04-48.fits[Details]10.490.16VISIR0.075177.0PARA8.045.00.0077.B-0137(A)HD1337742006-04-14T05:48:29Z2006-04-14T04:48:00Z0.052030.0017410771.5False270.510.1False271.919.90.480.3183.00.470.3398.0