Galaxy formation and evolution

Abstract:

Near infrared instrumentation at 4 and 8 meter class telescopes has grown rapidly in the past few years with the advent of 1024(2) and 2048(2) detector arrays. We present a brief review of high resolution spectroscopic capabilities available worldwide, with an eye on new developments, e.g. spatially resolved spectroscopy offered by integral field instruments.Observing at near-infrared wavelengths has its own quirks. We discuss observing strategies to get past the limits of high background (including both thermal background and background due to OH sky emission lines), Variations in atmospheric transmission, and detector constraints. Special attention is given to the subject of OH suppression/avoidance, which can significantly increase the sensitivity in the J, EI and short K windows. This is especially important for (fainter) high redshift targets, where the rest frame visible diagnostic lines are shifted into the near infrared.

Abstract:

We estimate the contribution of galaxies to the cosmic background flux at 912 Angstrom by means of an extended semi-analytic model of galaxy formation and evolution which takes into account the absorption of Lyman-limit photons by HI and dust in the interstellar medium (ISM) of the galaxies. We find that, though the background Lyman-limit flux escaping from galaxies is negligible compared to the flux from quasars at high redshifts, these two contributions become comparable at z similar or equal to 0.

Abstract:

We present a survey of molecular hydrogen line emission in nearby starburst and Seyfert galaxies. Excitation temperatures and gas masses for loci-lying energy levels of Hz are derived from the observed pure rotational lines. The H-2 (0-0) S(1) line in Seyferts is emitted by a "warm" gas at temperature of 120-140 K. This component accounts for 0.2-20 per cent of the total gas content. In starbursts the temperature of the S(1) emitting gas is somewhat higher (up to 210 K) and contributes typically a few per cent to the total gas mass (up to 9 per cent in M82). The S(5) and S(7) lines trace a "hotter" gas component at temperatures of about 1100K (up to 1700K in IC342) both in Seyfert and starburst galaxies. The excitation of the molecular hydrogen in starbursts and some of the Seyfert galaxies is dominated by UV-fluorescence. However it cannot be excluded that a part of the "warm" H-2 gas is thermally excited. For some of the Seyferts indications for shock excitation are found.