Aims. High angular resolution N-band imaging is used to discern the torus of active galactic nuclei (AGN) from its environment in order to allow a comparison of its mid-infrared properties to the expectations of the unified scenario for AGN. Methods. We present VLT-VISIR images of 25 low-redshift AGN of different Seyfert types, as well as N-band SEDs of 20 of them. In addition, we compare our results for 19 of them to Spitzer IRS spectra. Results. We find that at a resolution of ~ 0.35", all the nuclei of our observed sources are point-like, except for 2 objects whose extension is likely of instrumental origin. For 3 objects, however, we observed additional extended circumnuclear emission, even though our observational strategy was not designed to detect it. Comparison of the VISIR photometry and Spitzer spectrophotometry indicates that the latter is affected by extended emission in at least 7 out of 19 objects and the level of contamination is (0.20 ~ 0.85) * F_IRS. In particular, the 10 um silicate emission feature seen in the Spitzer spectra of 6 type I AGN, possibly 1 type II AGN and 2 LINERs, also probably originates not solely in the torus but also in extended regions. Conclusions. Our results generally agree with the expectations from the unified scenario, while the relative weakness of the silicate feature supports clumpy torus models. Our VISIR data indicate that, for low-redshift AGN, a large fraction of Spitzer IRS spectra are contaminated by extended emission close to the AGN.
There is an ongoing debate regarding the onset luminosity of dusty mass loss in population-II red giant stars. In this paper we present VISIR@VLT MIR 8.6 micron imaging of 47Tuc, centre of attention of a number of space-based Spitzer observations and studies. The VISIR high resolution (diffraction limited) observations allow excellent matching to existing optical Hubble space telescope catalogues. The optical-MIR coverage of the inner 1.15 arcmin of the cluster provide the cleanest possible, blending-free, sampling of the upper 3 magnitudes of the giant branch. Our diagrams show no evidence of…
The onset of the asymmetry of planetary nebulae (PNe) is expected to occur during the late Asymptotic Giant Branch (AGB) and early post-AGB phases of low- and intermediate-mass stars. Among all post-AGB objects, the most heavily obscured ones might have escaped the selection criteria of previous studies detecting extreme axysimmetric structures in young PNe. Since the most heavily obscured post-AGB sources can be expected to descend from the most massive PN progenitors, these should exhibit clear asymmetric morphologies. We have obtained VISIR-VLT mid-IR images of four heavily obscured post-AG…
[Abridged] Methods: We use interferometric observations in the $N$-band with VLTI/MIDI to resolve the mid-IR nucleus of IC 3639. The origin of the nuclear infrared emission is determined from: 1) the comparison of the correlated fluxes from VLTI/MIDI with the fluxes measured at subarcsec resolution (VLT/VISIR, VLT/ISAAC); 2) diagnostics based on IR fine-structure line ratios, the IR continuum emission, IR bands produced by polycyclic aromatic hydrocarbons (PAH) and silicates; and 3) the high-angular resolution spectral energy distribution. Results: The unresolved flux of IC 3639 is $90 \pm 20\…
The formation of the highest mass stars are thought to be dominated by instabilities resulting from gravitation and radiation. Instabilities due to gravitation are commonly demonstrated by observations of fragmentation, but those due to effects of radiation have thus far not been found. Here I report on the NACO adaptive optics and mid-infrared diffraction-limited VISIR imaging data of an extemely luminous ultra-compact HII region G333.6-0.2. Two infrared sources, one bright in the near-infrared(appearing point-like) and another in the mid-infrared (resolved with an elliptical shape) are uncov…
We analyze the gas and dust emission in the immediate vicinity of the supermassive black hole Sgr~A* at the Galactic center (GC) with the ESO VLT (Paranal/Chile) instruments SINFONI and VISIR. The SINFONI H+K data cubes show several emission lines with related line map counterparts. From these lines, the Br$γ$ emission is the most prominent one and appears to be shaped as a bar extending along the North-South direction. With VISIR, we find a dusty counterpart to this filamentary emission. In this work, we present evidence that this feature can be most likely connected to the mini-spiral and po…
[abridged] Our knowledge of the inner structure of embedded massive young stellar objects is still quite limited. We attempt here to overcome the spatial resolution limitations of conventional thermal infrared imaging. We employed mid-infrared interferometry using the MIDI instrument on the ESO/VLTI facility to investigate M8E-IR, a well-known massive young stellar object suspected of containing a circumstellar disk. Spectrally dispersed visibilities in the 8-13 micron range were obtained at seven interferometric baselines. We resolve the mid-infrared emission of M8E-IR and find typical sizes …
We present the first results from a mid-infrared survey of local Active Galactic Nuclei (AGN) using the CanariCam (CC) instrument on the 10.4m Gran Telescopio Canarias (GTC). We are obtaining sub-arcsecond angular resolution (0.3-0.6 arcsec) mid-IR imaging and spectroscopic observations of a sample of 100 local AGN, which are complemented with data taken with T-ReCS, VISIR, and Michelle. The full sample contains approximately 140 AGN, covers nearly six orders of magnitude in AGN luminosity, and includes low-luminosity AGN (LLAGN), Seyfert 1s and 2s, QSO, radio galaxies, and (U)LIRGs. The main …
The key ingredient of active galactic nuclei (AGN) unification, the dusty obscuring torus was so far held responsible for the observed mid-infrared (MIR) emission of AGN. However, the best studied objects with VLTI/MIDI show that instead a polar dusty wind is dominating these wavelengths, leaving little room for a torus contribution. But is this wind an ubiquitous part of the AGN? To test this, we conducted a straightforward detection experiment, using the upgraded VLT/VISIR for deep subarcsecond resolution MIR imaging of a sample of nine [O IV]-bright, obscured AGN, all of which were predicte…
We investigate the surroundings of the hypercompact HII region M17 UC1 to probe the physical properties of the associated young stellar objects and the environment of massive star formation. Five of the seven point sources in this region show $L$-band excess emission. Geometric match is found between the H_2 emission and near-IR polarized light in the vicinity of IRS5A, and between the diffuse mid-IR emission and near-IR polarization north of UC1. The H_2 emission is typical for dense PDRs, which are FUV pumped initially and repopulated by collisional de-excitation. The spectral types of IRS5A…
Recent high angular resolution observations resolved for the first time the mid-infrared (MIR) structure of nearby active galactic nuclei (AGN). Surprisingly, they revealed that a major fraction of their MIR emission comes from the polar regions. This is at odds with the expectation based on AGN unification, which postulates a dusty torus in the equatorial region. The nearby, archetypical AGN in the Circinus galaxy offers one of the best opportunities to study the MIR emission in greater detail. New, high quality MIR images obtained with the upgraded VISIR instrument at the Very Large Telescop…
Mid-Infrared (MIR) images of the Galactic center show extended gas and dust features along with bright IRS sources. Some of these dust features are a part of ionized clumpy streamers orbiting Sgr~A*, known as the mini-spiral. We present their proper motions over 12 year time period and report their flux densities in $N$-band filters {and derive their spectral indices}. The observations were carried out by VISIR at ESO VLT. High-pass filtering led to the detection of several resolved filaments and clumps along the mini-spiral. Each source was fit by a 2-D Gaussian profile to determine the offse…
This paper reports measurements of Sgr A* made with NACO in L' -band (3.80 um), Ks-band (2.12 um) and H-band (1.66 um) and with VISIR in N-band (11.88 um) at the ESO VLT, as well as with XMM-Newton at X-ray (2-10 keV) wavelengths. On 4 April, 2007, a very bright flare was observed from Sgr A* simultaneously at L'-band and X-ray wavelengths. No emission was detected using VISIR. The resulting SED has a blue slope (beta > 0 for nuL_nu ~ nu^beta, consistent with nuL_nu ~ nu^0.4) between 12 micron and 3.8 micron. For the first time our high quality data allow a detailed comparison of infrared and …
The QSO HE0450-2958 was brought to the front scene by the non-detection of its host galaxy and strong upper limits on the latter's luminosity. The QSO is also a powerful infrared emitter, in gravitational interaction with a strongly distorted UltraLuminous InfraRed companion galaxy. We investigate the properties of the companion galaxy, through new near- and mid-infrared observations of the system obtained with NICMOS onboard HST, ISAAC and VISIR on the ESO VLT. The companion galaxy is found to harbour a point source revealed only in the infrared, in what appears as a hole or dark patch in the…
Herbig-Haro flows are signposts of recent major accretion and outflow episodes. We aim to determine the nature and properties of the little-known outflow source HH 250-IRS, which is embedded in the Aquila clouds. We have obtained adaptive optics-assisted L-band images with the NACO instrument on the Very Large Telescope (VLT), together with N- and Q-band imaging with VISIR also on the VLT. Using the SINFONI instrument on the VLT we carried out H- and K-band integral field spectroscopy of HH 250-IRS, complemented with spectra obtained with the SpeX instrument at the InfraRed Telescope Facility …
The nature of circumstellar envelopes (CSE) around Cepheids is still a matter of debate. The physical origin of their infrared (IR) excess could be either a shell of ionized gas, or a dust envelope, or both. This study aims at constraining the geometry and the IR excess of the environment of the long-period Cepheid $\ell$ Car (P=35.5 days) at mid-IR wavelengths to understand its physical nature. We first use photometric observations in various bands and Spitzer Space Telescope spectroscopy to constrain the IR excess of $\ell$ Car. Then, we analyze the VLTI/MATISSE measurements at a specific ph…
In principle, the MID-infrared Interferometric instrument (MIDI) at the Very Large Telescope Array (VLTI) should always measure the same calibrated total flux spectrum for a specific source, independent of the instrument settings and the baseline geometry. In the data on the Circinus galaxy, however, there is (a) a general offset of the flux values for 2009 and (b) a slow drift of the total fluxes at short wavelengths during two nights (2008-04-17 and 2009-04-14). The latter seems to depend on the hour angle of the observation. In this document, a more detailed analysis of these two effects is…
We present new photometry of 16 local Seyferts including 6 Compton-thick sources in N-band filters around 12-microns, obtained with the VISIR instrument on the 8-m Very Large Telescope. The near-diffraction-limited imaging provides the least-contaminated core fluxes for these sources to date. Augmenting these with our previous observations and with published intrinsic X-ray fluxes, we form a total sample of 42 sources for which we find a strong mid-infrared:X-ray (12.3 micron:2-10 keV) luminosity correlation. Performing a physically-motivated sub-selection of sources in which the Seyfert torus…
