Bar pattern speeds in CALIFA galaxies

Context. About 35% of the nearby disc galaxies host a weak bar for which different formation scenarios, including the weakening of a strong bar and tidal interaction with a companion, have been suggested. Measuring the bar pattern speeds of a sample of weakly barred galaxies is a key step in constraining their formation process, but such a systematic investigation is still missing. Aims. We investigated the formation process of weak bars by measuring their properties in a sample of 29 nearby weakly barred galaxies, spanning a wide range of morphological types and luminosities. The sample galaxies were selected to have an intermediate inclination, a bar at an intermediate angle between the disc minor and major axes, and an undisturbed morphology and kinematics to allow the direct measurement of the bar pattern speed. Combining our analysis with previous studies, we compared the properties of weak and strong bars. Methods. We measured the bar radius and strength from the r band images available in the Sloan Digital Sky Survey and bar pattern speed and corotation radius from the stellar kinematics obtained by the Calar Alto Legacy Integral Field Area Survey. We derived the bar rotation rate as the ratio between the corotation and bar radii. Results. Thirteen out of 29 galaxies (45%), which were morphologically classified as weakly barred from a visual inspection, do not actually host a bar component or their central elongated component is not in rigid rotation. We successfully derived the bar pattern speed in 16 objects. Two of them host an ultrafast bar. Using the bar strength to differentiate between weak and strong bars, we found that the weakly barred galaxies host shorter bars with smaller corotation radii than their strongly barred counterparts. Weak and strong bars have similar bar pattern speeds and rotation rates, which are all consistent with being fast. We did not observe any difference between the bulge prominence in weakly and strongly barred galaxies, whereas nearly all the weak bars reside in the disc inner parts, contrary to strong bars. Conclusions. We ruled out that the bar weakening is only related to the bulge prominence and that the formation of weak bars is triggered by the tidal interaction with a companion. Our observational results suggest that weak bars may be evolved systems exchanging less angular momentum with other galactic components than strong bars

WEAVE spectrograph cameras: the polishing of the spherical lenses

WEAVE is the new wide field multi-object and integral field survey facility for the prime focus of the 4.2 m William Herschel Telescope. WEAVE fiber-fed spectrograph offers two resolutions, R 5000 and 20,000. The dual-beam spectrograph has two cameras: the blue one optimized for the wavelength interval of 366 - 606 nm and the red one for 579 - 959 nm. Each camera is formed by eight lenses, one aspherical and seven spherical. The lenses of the red camera are identical to the lenses of the blue camera only differentiated by the anti-reflection coating wavelength range. The diameter of the largest surface is 320 mm while of the smallest is 195 mm. INAOE, as a member of the collaboration is responsible of the manufacturing of the 14 spherical lenses and the collimator mirror. Here, we describe the main characteristics of WEAVE high precision cameras lenses, the manufacturing challenges giving the combination of OHARA glasses properties, dimensions and specifications. We discuss the solutions developed to achieve the very demanding specifications

The polishing of WEAVE spectrograph collimator mirror

International audienceWEAVE is the new wide field multi-object and integral field survey facility for the prime focus of the 4.2 m William Herschel Telescope. It is located at the Observatorio Roque de los Muchachos, in La Palma, Canary Islands, Spain. WEAVE fiber-fed spectrograph offers two resolutions, R 5000 and 20,000. It has a collimator mirror and two cameras optimized for the wavelength intervals of 366 - 959 nm and 579 - 959 nm, respectively. One of the responsibilities of INAOE within the WEAVE collaboration is the polishing of the collimator mirror, made of OHARA CLEARCERAM®- Z HS. The collimator has a diameter of 660 mm, a central thickness of 44.7 mm and a weight of 56.8 kg. The main specifications are: 2 fringes irregularity in a clear aperture of 624 mm diameter and a radius of curvature of 1224.65 mm +/- 0.15. In this work, we present the polishing process and final results for the collimator. In particular, we describe the tools developed for its manufacturing, the modifications carried out to the conventional polishing machine to support the glass. Additionally, the interferometric optical irregularity measurements are presented. The collimator polishing process is finished fulfilling all the optical specifications

Antireflective coatings for the red camera of WEAVE spectrograph

International audienceIn this work we present the coatings of the spectrograph red camera of WEAVE -the new multiobject survey facility for the 4.2m William Herschel Telescope. The initial requirements of WEAVE red camera lenses, with reflectances as low as 0.4% through the wavelength interval from 590 nm to 959 nm at angles of incidence of 18° +/- 17° represented a challenge for both design and production. Based on initial requirements, several solutions to the same problem were achieved and tested. The customized designs have been continuously improved through theoretical and experimental approximations. From transmittance measurements at normal incidence we developed a method to determine the reflectance at different angles of incidence. We show the designs and coating transmittance obtained for the four glasses on test runs to guarantee that the designs were achievable experimentally. Additionally, we present the reflectance obtained on the lenses of the the first four lenses of WEAVE red camera

WEAVE spectrograph cameras: the polishing of the spherical lenses

International audienceWEAVE is the new wide field multi-object and integral field survey facility for the prime focus of the 4.2 m William Herschel Telescope. WEAVE fiber-fed spectrograph offers two resolutions, R 5000 and 20,000. The dual-beam spectrograph has two cameras: the blue one optimized for the wavelength interval of 366 - 606 nm and the red one for 579 - 959 nm. Each camera is formed by eight lenses, one aspherical and seven spherical. The lenses of the red camera are identical to the lenses of the blue camera only differentiated by the anti-reflection coating wavelength range. The diameter of the largest surface is 320 mm while of the smallest is 195 mm. INAOE, as a member of the collaboration is responsible of the manufacturing of the 14 spherical lenses and the collimator mirror. Here, we describe the main characteristics of WEAVE high precision cameras lenses, the manufacturing challenges giving the combination of OHARA glasses properties, dimensions and specifications. We discuss the solutions developed to achieve the very demanding specifications

Thermal and mechanical design and test of the CCD mount for the WEAVE spectrograph cryostats

International audienceWEAVE is the new multi-object spectrograph for the William Herschel Telescope on La Palma. The culmination of prime focus, the large number of fibers and the wide resolution range has required a stringent optical design, which in turn demands a spectrograph with tight positional tolerances and large final focal plane. To capture this focal plane each of the two cryostats has two e2v 6k × 6k CCDs mounted as a mosaic. As well as being cooled to 150K via liquid nitrogen, the positional tolerances for the sensitive areas are flatness 60μm p-v over the entire image area, rotation around X and Y axis +/-50 arcmin, translation in X, Y and Z +/- 50 micron. We have used a Stil confocal measuring head mounted on two Thorlab translation stages to create a X,Y mount, controlled by a Raspberry Pi that is capable of recording measurements in Z to better than 1μm accuracy. This is used to measure the flatness and deformation of the image area under vacuum, and when cooled to 150K and the overall tip and tilt of the image plane to ensure they meet specification and are repeatable. In addition to this measuring system, we use a Thorlabs CMOS camera with a Navitar 50mm lens to ensure each CCDs image area is within specification with regards X and Y translation. In order to satisfy the above requirements, we designed the CCD mount to be adjustable (on initial setup), correctly constrained, isolated from liquid nitrogen boil-off vibration, and thermally insulating

The WEAVE prime focus correction: from design to integration

International audienceWEAVE is a new wide-field multi-object spectroscopy (MOS) facility proposed for the prime focus of the 4.2m William Herschel Telescope (WHT), situated on the island of La Palma, Canary Islands, Spain. To allow for the compensation of the effects of temperature-induced and gravity-induced image degradation, the WEAVE prime focus assembly will be translated along the telescope optical axis. The assembly comprises the prime focus corrector (PFC), a central mount for the corrector known as FTS[1], an instrument rotator and a twin-focal-plane fibre positioner. SENER, that manufactured and delivered the FTS, is also responsible for the final design, manufacturing, integration, alignment and testing of the PFC and its ancillary equipment. This manuscript describes the final design of the PFC along with the analyses and simulations performed and presents the procedures for the integration and alignment of the lenses in the corrector