Star formation in Damped Ly-Alpha Clouds

Team responsible: S. D'odorico (ESO)
Team members: N. Bouche, J. Liske, P. Moller, C. Peroux, M. Zwaan (ESO), M. Dessauges-Zavadsky (Obs. Geneve)

Finding charts: 0216+0800347-382206-192231-00152243-60

The scope of the observations is to explore the capabilities of SINFONI in imaging emission regions associated to H I -rich, high redshift Damped Lyman Systems in the line of sight to high z QSO. 2D spectroscopy in the IR has two advantages: access to the redshifted OII/OIII/H-alpha/H-beta lines from the DLA galaxy and the superior seeing quality in the IR (and eventually the AO advantage when the Laser Guide Star facility will be available) to separate the QSO from the galaxy. The targets of our mini-survey have been selected carefully according to previous observations in the optical, redshifts, expected star formation rate and metallicity to ensure that the lines in question be bright. The final science goals are the properties of these class of galaxies identified up to redshift z~5 by measuring their impact-parameter (proxy for size), absolute and relative line-flux (proxy for star-formation-rate and metallicity) and line width (proxy for mass).

Target list
NameRA(2000)DEC(2000)Plate-Scale(s)Bands(s)Exp.time(on source)
0216+08002:18:57.33+08:17:27.75250H+K2 h
0347-3803:49:43.68-38:10:31.3250H2 h
2206-1922:08:52.07-19:43:59.50100J1.5 h
2231-001522:34:09.0+00:00:01.7250H2 h
2243-603122:47:08.8-60:15:46250K2 h

Science Scope:
Damped Lyman-α (hereafter DLAs) systems seen in absorption in the spectrum of high-redshift quasars are a complementary observational tool to the study of high-redshift Universe. Some of their properties (HI gas content, metallicity, molecular content) are rather well constrained by observations in absorption but their connection to other high-redshift galaxies (i.e. LBGs)is much debated and remains to be firmly established. Since metals in a range of abundances are measured in DLAs, then star formation must be associated with the systems. Over the past few years attempts to image the galaxies responsible for DLAs have proven challenging. Previous observational methods include broad-band imaging (Le Brun et al. 1997, A & A, 321, 733; Moller et al. 1998, MNRAS 299, 661), Lyα narrow-band imaging (Lowenthal et al. 1995, ApJ, 451, 484; Bunker et al. 1999, MNRAS, 309, 875), ground-based and space-based Hα narrow-band imaging and spectroscopic surveys.

SINFONI allows to probe the IR bands where redshifted OII/OIII/Hα/Hβ lines from the z~2-3 DLA galaxies are expected to fall. Furthermore, the IFU combines the advantages of both the imaging and spectroscopy.For most of the observations the 8 x 8 arcsec field of the instrument will be used and no AO correction will be applied. The QSO with the DLAs in the line of sight are too faint for an efficient use of the SINFONI AO system. Working in the IR has however the advantage of a superior IQ in good seeing conditions, which should permit an easier detection of emission objects at small impact angle from the QSO. Depending on the result of this survey, a large exploration of the DLA could be carried out when the Laser Guide Star facility will become available. The final science goals of the program are the properties of these class of galaxies up to redshift z~5 by measuring their impact-parameter (proxy for size), absolute and relative line-fluxes (proxy for star-formation-rate and metallicity) and line width (proxy for mass)

The observational strategy is first to extend the study of emission lines in Q2206 DLA (z=1.92) for which Moller et al. (2002; ApJ 574, 51) have detected Lyα at blue wavelengths. Other targets are carefully selected so that: (1) their redshifted emission lines fall in SINFONI transmission bands and do not overlap with strong sky emission or absorption bands, (2) they have a signature for strong emission associated to star forming activity ( either from their relatively high metallicity, or absorption line ratios).