3. Estado del arte
3.4. El uso e Integración de las TIC de manera didáctica
over a FOV of 0.800×0.800, 800×800, and 3.200×3.200respectively. The spectral resolution
of the spectrometer ranges between 2000 and 4000 for the three covered atmospheric bands: J(1.1−1.4µm), H(1.45−1.85µm) and K(1.95−2.45µm). The instrument is fully cryogenic, and it is equipped with a Rockwell 2k×2k HAWAII-2RG array. Figure 1.5 shows an inside view of the main components of SPIFFI. The light enters from the top. The pre-optics with a filter wheel re-image the object plane from the AO module onto the image slicer, providing the three different image scales. The im- age slicer rearranges the two dimensional field onto a one-dimensional pseudo longslit. A grating wheel disperses the light and a short focal length camera then images the spectra on the detector. After some processing of the raw data, the outcome is a data cube with two spatial and one spectral dimensions.
1.4
The nearby AGN SINFONI sample
In order to study the characteristics of a class of galaxies such as Seyferts, ideally one would observe all members of that class. As this is impractical for many reasons, such studies rely on the analysis of a sample of sources that are chosen to be representative of the class as a whole. However, depending on the selection criteria for a sample, slight biases may be introduced. The nearby AGN SINFONI sample includes Type 1 and Type 2 Seyfert galaxies. Source selection was driven principally by technical considerations, being the primary criteria for selecting AGN that:
1. the nucleus should be bright enough for adaptive optics correction,
2. the galaxy should be close enough that small spatial scales can be resolved at the near-infrared diffraction limit of an 8-m telescope, and
3. the galaxies should be “well known” so that complementary data can be found in the literature
The resulting sample of 7 AGN is listed in Table 1.1. Thus, while the sample can- not be considered complete, it provides a representative cross-section of AGN. As an incomplete sample of Seyferts, a bias is introduced towards Type 1 objects. However, this bias can itself be considered a strength for the nuclear star formation studies, since it is exactly broad line AGN for which little is known about this issue, because as mentioned in Section 1.2.3, the glare of the AGN overshines any surrounding stellar light in the central arcsec.
This dissertation presents results of the observations of two AGN (the Circinus galaxy and NGC 1068). Remarkably but unintentionally, they are the only two Seyfert 2 galaxies in our sample. They were selected for detailed individual analysis due to their importance in the research field of AGN. It is important to point out that NGC3227 has already been studied by Davies et al. (2006), and the rest of the objects
16 CHAPTER 1. INTRODUCTION TO THE NEARBY AGN PROJECT
1.4. THE NEARBY AGN SINFONI SAMPLE 17
Object Classification Distance Observed Band Resolution Date of observation
(Mpc) (00)
Circinus Sy2 4 K 0.22 July 2004
NGC1068 Sy2 14 H+K 0.075 October 2005
NGC3227 Sy1 17 K 0.085 December 2004
NGC1097 LINER, Sy1 18 H+K 0.245 October 2005
NGC2992 Sy1 33 K 0.3 March 2005
NGC3783 Sy1 42 H+K 0.17 March 2005
NGC7469 Sy1 66 K 0.15 July 2004
Table 1.1: The Nearby AGN SINFONI Sample.
in the sample are currently being analysed. On the other hand, following a different analysis strategy, Davies et al. (2007) have studied the issue of star formation in the nuclei of these 7 Seyfert galaxies (including the results from the Circinus galaxy and NGC1068) and two more for which we have already published adaptive optics near infrared spectra (Davies et al. 2004a, Davies et al. 2004b).
Chapter 2
Case study: The Circinus Galaxy
This chapter is an almost exact reproduction of the publication:
• “SINFONI adaptive optics integral-field spectroscopy of the Circinus Galaxy” M¨uller S´anchez, F., Davies, R. I., Eisenhauer, F., Tacconi, L. J., Genzel, R., & Sternberg, A. 2006, A&A, 454, 481
20 CHAPTER 2. THE CIRCINUS GALAXY
2.1
Introduction
In the context of active galactic nuclei, star formation activity and the gas and stellar dynamics on scales of a few parsecs to a few tens of parsecs can be counted among the main debated issues. The unified model of active galaxies (see Lawrence 1987 for a review) assumes that the inner region of Seyfert 2 galaxies is comprised of a dense circumnuclear torus that hides the nucleus and the broad-line region from our line of sight at near-infrared and optical wavelengths. The size scales on which models predict the canonical torus vary from an inner edge at 1 pc out to several tens of parsecs (Pier & Krolik 1992; Nenkova et al. 2002; Schartmann et al. 2005). These crucial size scales are exactly those that can be resolved with SINFONI in the nearest AGN.
The Circinus galaxy, at a distance of 4.2±0.8 Mpc (Freeman et al. 1977), is an ideal subject to study because of its proximity (100 = 20 pc). It is a large, highly
inclined (i = 65◦ Freeman et al. 1977), spiral galaxy that hosts both a typical
Seyfert 2 nucleus and a circumnuclear starburst on scales of 100–200 pc (Maiolino et al. 1998). Evidence for an obscured Seyfert 1 nucleus is provided by the finding of a broad (FWHM = 3300 kms−1) Hα line component in polarized light (Oliva et al. 1998). Their picture is also supported by recent X-ray observations. Those above 10 keV suggest direct X-ray detection of the nucleus through a column density of 4×1024cm−2 (Matt et al. 1999). The X-ray spectrum below 10 keV exhibits a flat continuum and a very prominent iron line, indicative of Compton scattering and fluorescent emission from gas illuminated by an obscured X-ray continuum source (Matt et al. 1996). Circinus shows highly ionized gas extending along the minor axis of the galaxy, with a morphology that is reminiscent of the ionization cones seen in other Seyfert galaxies (Marconi et al. 1994a). H2O maser emission has been detected, and the masing gas traces a thin accretion disk about 0.4 pc in radius, and so does the inner 10µm dust emission from the VLTI (Tristram et al. 2007). In addition, a fraction of the masers originates outside the disk, in what appears to be an outflow within ∼1 pc of the nucleus and aligned with the ionization cone (Greenhill et al. 2003). Optical and near-infrared spectrophotometry of the nucleus show a typical Seyfert spectrum, including strong coronal lines (Oliva et al. 1994; Prieto et al. 2004). There are also lines from H2 and low-excitation ionic species, both believed to be associated with starforming regions. The distribution and kinematics of the Brγ line have been interpreted in terms of ongoing star formation activity within a few tens of parsecs of the active nucleus (Maiolino et al. 1998). A young stellar population with an age between 4×107 and 1.5×108 was found between these scales. Recent observations of the Circinus Galaxy in the range between 1−10µm (Prieto et al. 2004), resolve aKs-band source with a FWHM of ∼2 pc and a spectral energy
distribution compatible with a dust temperature of 300 K.
This chapter presents high-resolution, nearly diffraction-limited integral-field spec- troscopic data of the Circinus galaxy in theK-band observed with the adaptive optics
2.2. OBSERVATIONS AND DATA REDUCTION 21