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Register a new userA fresh view on Henize 2-10 with VLT/NAOS-CONICA
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We present high-resolution observations of Henize 2-10 in Ks (2.2um), L (3.8um), M (4.8um) bands. These allow for the first time to track accurately the structures at the heart of the galaxy from the optical to the radio. All radio knots previously observed can now be associated with L and Ks emitting regions. This implies a revision of their physical nature. Instead of highly extinguished ultra-dense HII regions, we propose that two of the 5 radio knots are either supernova remnants or normal HII regions, while the remaining three are bona fide ultra-dense HII regions, although less obscured than was previously thought.
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We report on Galactic Center L-band observations made during NAOS/CONICA Science Verification. Colors of the inner 2 stars reveal an infrared excess of S2, the closest star to the black hole, that could sign the first thermal infrared detection of Sgr A*. A multi-wavelength maximum likelihood analysis has allowed us to eliminate all but two of the candidates for gravitational lensing proposed by Alexander (2001). Our observations of the thin and intersecting structures of the Northern Arm could trace several shocks heating the neighbooring dust rather than a stream of matter in orbit around the central mass as previously thought.
Adaptive optics (AO) allows one to derive the point spread function (PSF) simultaneously to the science image, which is a major advantage in post-processing tasks such as astrometry/photometry or deconvolution. Based on the algorithm of citet{veran97}, PSF reconstruction has been developed for four different AO systems so far: PUEO, ALFA, Lick-AO and Altair. A similar effort is undertaken for NAOS/VLT in a collaboration between the group PHASE (Onera and Observatoire de Paris/LESIA) and ESO. In this paper, we first introduce two new algorithms that prevent the use of the so-called $U_{ij}$ functions to: (1) avoid the storage of a large amount of data (for both new algorithms), (2) shorten the PSF reconstruction computation time (for one of the two) and (3) provide an estimation of the PSF variability (for the other one). We then identify and explain issues in the exploitation of real-time Shack-Hartmann (SH) data for PSF reconstruction, emphasising the large impact of thresholding in the accuracy of the phase residual estimation. Finally, we present the data provided by the NAOS real-time computer (RTC) to reconstruct PSF ({em (1)} the data presently available, {em (2)} two NAOS software modifications that would provide new data to increase the accuracy of the PSF reconstruction and {em (3)} the tests of these modifications) and the PSF reconstruction algorithms we are developing for NAOS on that basis.
We report on the first results obtained using adaptive optics measurements of the Galactic Centre done with NAOS/CONICA.
We present ALMA CO(3-2) observations at 0.3 arcsec resolution of He2-10, a starburst dwarf galaxy and possible high-z galaxy analogue. The warm dense gas traced by CO(3--2) is found in clumpy filaments that are kinematically and spatially distinct. The filaments have no preferred orientation or direction; this may indicate that the galaxy is not evolving into a disk galaxy. Filaments appear to be feeding the active starburst; the velocity field in one filament suggests acceleration onto an embedded star cluster. The relative strengths of CO(3-2) and radio continuum vary strongly on decaparsec scales in the starburst. There is no CO(3--2) clump coincident with the non-thermal radio source that has been suggested to be an AGN, nor unusual kinematics. The kinematics of the molecular gas show significant activity apparently unrelated to the current starburst. The longest filament, east of the starburst, has a pronounced shear of FWHM $sim40$~kms across its $sim$50~pc width over its entire $approx 0.5$ kpc length. The cause of the shear is not clear. This filament is close in projection to a `dynamically distinct CO feature previously seen in CO(1--0). The most complex region and the most highly disturbed gas velocities are in a region 200~pc south of the starburst. The CO(3--2) emission there reveals a molecular outflow, of linewidth FWZI $sim$ 120-140 kms, requiring an energy $gtrsim 10^{53} rm~ erg/s$. There is at present {it no} candidate for the driving source of this outflow.
The rate of star formation both in the Galaxy and in external galaxies should be related to the physical properties of the molecular clouds from which stars form. This is expected for the starbursts found both in irregular galaxies and in some mergers. The dwarf galaxy Henize 2-10 is particularly interesting in this context as it shows a number of newly formed Super Star Clusters (SSCs) associated with a very rich molecular environment. We present a high angular resolution study of the molecular gas associated with the SSCs with the aim of deriving the physical properties of the parent molecular clouds. The final goal is to test the expectation that the formation of SSCs requires exceptionally dense and massive clouds. We have used the Submillimeter Array with an angular resolution of 1.9 X 1.3 to map the J=2-1 transition of CO in Henize 2-10. Supplementary measurements of HCN(J=1-0), 13CO(J=2-1) and millimeter continuum were obtained with the APEX, IRAM-30m and SEST single dish telescopes. Our single dish observations confirm the association of the newly formed SSCs in Henize 2-10 with dense molecular gas. Our interferometric observations resolve the CO(2-1) emission in several giant molecular clouds. Overall the molecular gas accounts for approximately half of the mass in the central regions of Henize 2-10. Although we find indications that the molecular clouds associated with the formation of SSCs in Henize 2-10 are massive and dense, the tracer we used (CO) and the linear resolution of our observations (60 X 80 pc) are still not adequate to test the expectation that exceptionally dense and massive cores are required for SSCs formation.
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