We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise HST data, and spectra of six SNe Ia that were discovered during 2001 are presented. Additionally, for the two SNe with z > 1, we present groundbased J-band photometry from Gemini and the VLT. These are among the most distant SNe Ia for which ground based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation (Kowalski et al. 2008). We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 supernovae, the Union2

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SPECTRA AND HUBBLE SPACE TELESCOPE LIGHT CURVES OF SIX TYPE Ia SUPERNOVAE AT 0.511 <z< 1.12 AND THE UNION2 COMPILATION ∗

Context: Lyman-alpha (Lyα) radiation is now widely used to investigate the galaxy formation and evolution in the high redshift universe However, without a rigorous understanding of the processes regulating the Lyα escape fraction, physical interpretations of high-z observations remain questionable Aims: We examine six nearby star forming galaxies to disentangle the role of the dust from other parameters such as gas kinematics, geometry, and ISM morphology in the obscuration of Lyα Thereby, we attempt to understand the Lyα escape physics and infer the implications for high-redshift studies Methods: We use HST/ACS imaging to produce continuum-subtracted Lyα maps, and ground-based observations (ESO/NTT and NOT) to map the Hα emission and the extinction E(B-V) in the gas phase derived from the Balmer decrement Hα/Hβ Results: When large outflows are present, the Lyα emission does not appear to be correlated with the dust content, confirming the role of the Hi kinematics in the escape of Lyα photons In the case of a dense, static Hi covering, we observe a damped absorption with a negative correlation between Lyα and E(B-V) We found that the Lyα escape fraction does not exceed 10% in all our galaxies and is mostly about 3% or below Finally, because of the radiative transfer complexity of the Lyα line, star formation rate based on Lyα luminosity is underestimated with respect to that derived from UV luminosity Simple reddening correction does not reconcile SFR(Lyα) with the total star formation rate Conclusions: The dust is not necessarily the main Lyα escape regulatory factor ISM kinematics and geometry may play a more significant role The failure of simple dust correction to recover the intrinsic Lyα/Hα ratio or the total star formation rate should prompt us to be more cautious when interpreting high-z observations and related properties, such as SFRs based on Lyα alone To this end, we propose a more realistic calibration for SFR(Lyα), which accounts for dust attenuation and resonant scattering effects via the Lyα escape fraction

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On the Detectability of Lyman-alpha Emission in Star-forming Galaxies: The Role of Dust

We present Very Large Telescope (VLT) and Magellan spectroscopy and New Technology Telescope photometry of nine faint cataclysmic variables (CVs) which were spectroscopically identified by the Sloan Digital Sky Survey (SDSS). We measure orbital periods for five of these from the velocity variations of the cores and wings of their H alpha emission lines. Four of the five have orbital periods shorter than the 2-3 h period gap observed in the known population of CVs. SDSS J004335.14-003729.8 has an orbital period of P-orb = 82.325 +/- 0.088 min; Doppler maps show emission from the accretion disc, bright spot and the irradiated inner face of the secondary star. In its light curve, we find a periodicity which may be attributable to pulsations of the white dwarf. SDSS J163722.21-001957.1 has P-orb = 99.75 +/- 0.86 min. By combining this new measurement with a published superhump period, we estimate a mass ratio of q approximate to 0.16 and infer the physical properties and orbital inclination of the system. For SDSS J164248.52+134751.4, we find P-orb = 113.60 +/- 1.5 min. The Doppler map of this CV shows an unusual brightness distribution in the accretion disc which would benefit from further observations. SDSS J165837.70+184727.4 had spectroscopic characteristics which were very different between the SDSS spectrum and our own VLT observations, despite only a small change in brightness. We measure P-orb = 98.012 +/- 0.065 min from its narrow H alpha emission line. Finally, SDSS J223843.84+ 010820.7 has a comparatively longer period of P-orb = 194.30 +/- 0.16 min. It contains a magnetic white dwarf and, with g = 18.15, is brighter than the other objects studied here. These results continue the trend for the fainter CVs identified by the SDSS to be almost exclusively shorter period objects with low mass transfer rates.

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Orbital periods of cataclysmic variables identified by the SDSS – V. VLT, NTT and Magellan observations of nine equatorial systems

Context. The region of the Small Magellanic Cloud (SMC) with which this paper is concerned contains the highest concentration of IRAS/Spitzer sources, H i emission, and molecular clouds in this neighboring galaxy. However, it has been the target of very few studies, despite this evidence of star formation. Aims. We present the first detailed study of the compact H ii region N33 in the SMC by placing it in a wider context of massive star formation. Moreover, we show that N33 is a particularly interesting candidate for isolated massive star formation. Methods. This analysis is based mainly on optical ESO NTT observations, both imaging and spectroscopy, coupled with other archive data, notably Spitzer images (IRAC 3.6, 4.5, 5.8, and 8.0 μm) and 2MASS observations. Results. We derive a number of physical characteristics of the compact H ii region N33 for the first time. This gas and dust formation of 7. �� 4 (2.2 pc) in diameter is powered by a massive star of spectral type O6.5-O7 V. The compact H ii region belongs to a rare class of H ii regions in the Magellanic Clouds, called high-excitation blobs (HEBs). We show that this H ii region is not related to any star cluster. Specifically, we do not find any traces of clustering around N33 on scales larger than 10 �� (∼3 pc). On smaller scales, there is a marginal stellar concentration, the low density of which, below the 3σ level, does not classify it as a real cluster. We also verify that N33 is not a member of any large stellar association. Under these circumstances, N33 is also therefore attractive because it represents a remarkable case of isolated massive-star formation in the SMC. Various aspects of the relevance of N33 to the topic of massive-star formation in isolation are discussed.

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An interesting candidate for isolated massive-star formation in the Small Magellanic Cloud

We present time-series VLT spectroscopy and NTT photometry of the cataclysmic variable SDSS J220553.98+115553.7, which contains a pulsating white dwarf. We determine a spectroscopic orbital period of Porb = 82.825± 0.089 min from velocity measurements of the Ha emission line. A period analysis of the light curves reveals a dominant periodicity at Pphot = 44.779± 0.038 min which is not related to the spectroscopic period. However, the light curves do not exhibit a variation at any frequency which is attributable to GW Lib-type pulsations, to a detection limit of 5 mmag. This non-detection is in contrast to previous studies which have found three pulsation frequencies with amplitudes of 9‐11 mmag at optical wavelengths. Destructive interference and changes to the thermal properties of the driving layer in direct response to accretion can be ruled out as causes of the non-detection. Alternatively, it is feasible that the object has cooled out of the instability strip since a previous (unobserved) dwarf nova superoutburst. This would be the first time this behaviour has been seen in a cataclysmic variable pulsator. Another possibility is that changes in the surface characteristics, possibly induced by accretion phenomena, have modified the surface visibility of the pulsation modes. Further observations, particularly improved constraints on the timescale for changes in the mode spectrum, are needed to distinguish among possible explanations.

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Orbital periods of cataclysmic variables identified by the SDSS - IV. SDSS J220553.98+115553.7 has stopped pulsating

We present the characteristics of the new CCD imager, SUSI2, installed at the ESO 3.5 m NTT. The instrument shares the Nasmyth focus A with the new infrared imager-spectrograph SOFI. The focal plane array of USSI2 is a mosaic of 2 EEV44- 82, 2k X 4k, 15 micrometer pixels, thinned, anti-reflection coated CCDs, which are placed at the direct focus of the telescope (scale 0.08 arcsec/pixel, field of view 5.5 X 5.5 arcmin). The average QE for the two devices is 76, 90, 85, 80, 68, 49, 23% at 350, 400, 500, 600, 700, 800, 900 nm respectively. The overall instrument efficiency, including the three mirrors of the telescope and the detector but without filters, is computed to be 46, 55, 51, and 48% at the central wavelengths of the U, B, V and R bands. The CCDs are driven by the new ESO CCD controller FIERA. The system performance was measured during the commissioning of the instrument at the telescope in February 98. The mosaic is read in 16 seconds in the standard operating mode (2 X 2 binning of the CCDs) with a read-out-noise of 4.7 e-/pixel. The other CCD parameters such as CTE, dark current and linearity, were also found to comply with the requirements. The FWHM of stellar sources in images obtained in good seeing conditions were measured to be 0.49 arcsec, with no significant variation over the field of view.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Commissioning of a 4Kx4K CCD mosaic and the new ESO FIERA CCD controller at the SUSI-2 imager of the NTT

VIMOS is the visible (360 to 1000 nm) wide-field imager and multi-object spectrograph mounted on the Nasmyth focus B of Melipal (UT3) (Le Fevre et al. 003). The instrument is comprised of four identical arms each with a field of view of 7; × 8; with a 0. 05? pixel size and a gap between each quadrant of ~ ;. Each arm is equipped with six grisms providing a spectral resolution range from ~ 00– 500 and with an EEV 44-8 , thinned, anti-reflection coated, 4k × k pixel CCD. VIMOS operates in three different modes: Imaging (IMG), Multi-Object Spectroscopy (MOS), and with Integral Field Unit (IFU). For a summary of the instrument capability and performance, see http:// www.eso.org/instruments/vimos/

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Gianni Marconi

Papers

Commissioning of a 4Kx4K CCD mosaic and the new ESO FIERA CCD controller at the SUSI-2 imager of the NTT

New, Efficient High-Resolution Red VPH Grisms in VIMOS