Using the OSIRIS tunable narrow band imager on the 10.4m GTC (La Palma) we have mapped the SAB(rs)cd galaxy NGC 6946 over a 7.3x7.5 square arcminutes field in the emission lines of the [SII]\lambda\lambda, 6717, 6731 doublet, and in H\alpha. From these maps we have produced catalogs of the H\alpha luminosities and effective radii of 557 HII regions across the disk, and derived the [SII] emission line ratios of 370 of these. The H\alpha observations were used to derive the mean luminosity-weighted electron densities for the regions of the sample, while the [SII] line ratios allowed us to derive values of the in situ electron densities in the denser zones from which the major fraction of the radiation in these lines is emitted, for 58 of the regions. This is by far the largest data set of its kind for a single galaxy. A classical two phase model is used to derive the filling factors of the regions. We find that although the mean electron density decreases with the square root of the radius of the regions, the in situ density is essentially independent of this radius. Thus the filling factor falls systematically, as the radius and the luminosity of the regions increases, with a power law of exponent -2.23 between filling factor and radius. These measurements should enhance the perspectives for more refined physical models of HII regions.
It may interest you
We present the results of our spatially resolved investigation into the interplay between the ages of the stellar populations and the kinematics of the warm ionised outflows in the well-studied type II quasar Markarian 34. Utilising integral field spectroscopic (IFS) data, we determine the spatial distribution of the young stellar population (YSP; age < 100 Myr) using spectral synthesis modelling. We also employ the 5007 [OIII] emission line as a tracer of the warm ionised gas kinematics. We demonstrate a spatial correlation between the outer edges of the advancing side of the outflow and anAdvertised on
A numerical experiment conducted by two researchers at the Instituto de Astrofísica de Canarias (IAC), Daniel Nöbrega Siverio and Fernando Moreno Insertis, has allowed them to show, for the first time, how one of the most widely distributed structures in the solar atmosphere, the coronal bright points, can form and acquire energy by the action of the solar granulation. When the Sun is observed from space detectors of X-rays or the extreme-ultraviolet, its atmosphere is found to be full of bright points, both during solar active epochs when a large number of sunspots is observed, and duringAdvertised on
The confirmation of the existence of black holes is one of the most basic results in astrophysics. There is a wide range of masses of black holes, from those with stellar mass, which are the result of the catastrophic final phase of very massive stars, to the supermassive black holes at the centres of most galaxies. The mass of a black hole is up to now the only parameter which scientists are able to measure. In this work, we present an original method for measuring the masses of black holes, from those of stellar mass to the supermassive variety, based on a simple measurement of theAdvertised on