Arcmin Field Of View Research Articles

CONCERTO: Instrument and status

CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn) is a low-resolution Fourier transform spectrometer dedicated to the study of star-forming galaxies and clusters of galaxies in the transparent millimeter windows from the ground. It is characterized by a wide instantaneous 18.6 arcmin field of view, operates at 130–310 GHz, and was installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5 100m above sea level. CONCERTO’s double focal planes host two arrays of 2 152 kinetic inductance detectors and represent a pioneering instrument to meet a state-of-the-art scientific challenge. This paper introduces the CONCERTO instrument and explains its status, shows the first CONCERTO spectral maps of Orion, and describes the perspectives of the project.

Optimizing the location of multiple laser guide stars in ground layer adaptive optical systems

At present, the ground layer adaptive optical systems are using multiple laser guide stars arranged in regular polygons as reference targets to measure the effects of atmospheric turbulence. Obtaining the optimal position of laser guide stars becomes an interesting problem to analyze. This paper proposes a method to obtain the optimal position of laser guide stars by using a genetic algorithm as the optimization algorithm and a simplified geometry model of the ground layer adaptive optic system as the evaluation function. Furthermore, multi-process, Numba library, and multi-thread techniques methods are used to accelerate calculation speed. Based on these methods, real atmospheric turbulence profiles are used to analyze the relationship between the optimal position of laser guide stars with different numbers and the different atmospheric turbulence profiles from the same site, through an example of a ground layer adaptive optics system with 14 arcmin field of view. The results show that the optimal position of laser guide stars in the same site is almost the same and their statistically optimal positions are all regular polygon. Besides, we also find that the spatial resolution of turbulence profiles has strong effects to positions of laser guide stars, showing that the more equivalent layers in the measurement results, the closer the position distribution of laser guide stars is to the regular polygon.

Highly sensitive polarimetric camera (B-BOP) for the SPICA mission.

The Space Infrared telescope for Cosmology and Astrophysics (SPICA) mission has just been selected by the European Space Agency as one of the three candidate missions to be further studied for the medium size mission M5. B-BOP, formerly named POL, is one of the three scientific instruments of SPICA which aims, among other scientific goals, to map the galactic filamentary structures and their associated magnetic fields. With a novel interlaced-shaped design, B-BOP will contain 1344 pixels, operating within a temperature range of 50-100mK, covering a 2.6 arcmin field of view, and delivering imaging polarimetry in three spectral bands: 100μm, 200μm, and 350μm simultaneously. In this paper, we investigate by numerical simulations the mechanical, electromagnetic, and thermoelectric behaviors of B-BOP detectors and predict for the three bands (i)a sufficient mechanical stability, (ii)a good electromagnetic absorption higher than 95%, (iii)a high response value better than 1011 V/W, and (iv)especially a very low noise equivalent power reaching 1 aW/Hz1/2 at 50mK.

ARGOS at the LBT

Having completed its commissioning phase, the Advanced Rayleigh guided Ground-layer adaptive Optics System (ARGOS) facility is coming online for scientific observations at the Large Binocular Telescope (LBT). With six Rayleigh laser guide stars in two constellations and the corresponding wavefront sensing, ARGOS corrects the ground-layer distortions for both LBT 8.4 m eyes with their adaptive secondary mirrors. Under regular observing conditions, this set-up delivers a point spread function (PSF) size reduction by a factor of 2–3 compared to a seeing-limited operation. With the two LUCI infrared imaging and multi-object spectroscopy instruments receiving the corrected images, observations in the near-infrared can be performed at high spatial and spectral resolution. We discuss the final ARGOS technical set-up and the adaptive optics performance. We show that imaging cases with ground-layer adaptive optics (GLAO) are enhancing several scientific programmes, from cluster colour magnitude diagrams and Milky Way embedded star formation, to nuclei of nearby galaxies or extragalactic lensing fields. In the unique combination of ARGOS with the multi-object near-infrared spectroscopy available in LUCI over a 4 × 4 arcmin field of view, the first scientific observations have been performed on local and high-z objects. Those high spatial and spectral resolution observations demonstrate the capabilities now at hand with ARGOS at the LBT.

The impact of ELT distortions and instabilities on future astrometric observations

The paper discusses an assessment study about the impact of the distortions on the astrometric observations with the Extremely Large Telescope originated from the optics positioning errors and telescope instabilities. Optical simulations combined with Monte Carlo approach reproducing typical inferred opto-mechanical and dynamical instabilities, show RMS distortions between $\sim$ 0.1-5 mas over 1 arcmin field of view. Over minutes timescales the plate scale variations from ELT-M2 caused by wind disturbances and gravity flexures and the field rotation from ELT-M4-M5 induce distortions and PSF jitter at the edge of 1 arcmin FoV (radius 35 arcsec) up to $\sim$ 5 mas comparable to the diffraction-limited PSF size $FWHM_H = 8.5$ mas. The RMS distortions inherent to the ELT design are confined to the 1$^{st}$-3$^{rd}$ order and reduce to an astrometric RMS residual post fit of $\sim$ 10-20 $\mu as$ for higher order terms. In this paper, we study which calibration effort has to be undertaken to reach an astrometric stability close to this level of higher order residuals. The amplitude and timescales of the assumed telescope tolerances indicate the need for frequent on-sky calibrations and MCAO stabilization of the plate scale to enable astrometric observations with ELT at the level of $\leq 50 \mu as$, which is one of the core science missions for the ELT / MICADO instrument.

OUP accepted manuscript

The Chinese Large Optical/Infrared Telescope is currently undergoing design studies. A ground-layer adaptive-optics system (GLAO) has been proposed, with a 14 -arcmin field of view (FOV) and moderate adaptive-optics correction using a deformable secondary mirror, several laser guide stars (LGS) and wavefront sensors. Due to its large FOV and relatively complex structure, some important problems should be analysed to aid budget considerations for the whole telescope. In this paper, we propose a FOV-related evaluation factor to describe the GLAO performance and use an end-to-end Monte Carlo simulation to test its performance under different configurations. To accelerate the parameter space exploration speed, we split the parameter space of the GLAO system and apply a bottom-up search procedure for parameter selection. We also propose a simplified turbulence geometric model to evaluate the GLAO performance with different turbulence-profile-related parameters. With the above methods, we analyse the required number of deformable mirror (DM) actuators, the number, position and magnitude of LGS and explore the DM tilt-conjugation problem for this GLAO system.

The potential of using KMOS for multi-object massive star spectroscopy

AbstractKMOS, the “K-Band Multi-Object Spectrometer”, was built by a British-German consortium as a second generation instrument for the ESO Paranal Observatory. It is available to the user community since its successful commissioning in 2013 (Sharples et al. 2013). As a multi-object integral field spectrometer for the near infrared, KMOS offers 24 deployable IFUs of 2.8x2.8 arcsec and 14x14 spatial pixels each, which can either be placed individually within a 7.2 arcmin field of view or combined in a Mosaic mode in order to map contiguous fields on sky. The instrument covers the whole range of NIR atmospheric windows (0.8. . .2.5μm) with 5 spectral bands and a resolution of R ≈ 3000. . .4000.Although the main science driver for KMOS was to enable the study of galaxy formation and evolution through multiplexed observations of high-redshift galaxies, KMOS also already exhibited its tremendous potential for the spectroscopy of massive stars: A quantitative study of 27 RSGs in NGC 300 (Gazak et al. 2015) proves its applicability for the spectroscopy of individual stars even beyond the Local Group. A Mosaic observation of the Galactic centre (Feldmeier-Krause et al. 2015) demonstrates how spectra of early-type stars can be extracted from a contiguous field. Other applications include (but need not be limited to) velocity determinations of globular cluster stars, observations of jets/outflows of high mass protostars, or contiguous mapping of star-forming regions.We therefore aim at presenting the excellent capabilities of KMOS to a wider community and indicate potential applications.

CHIMERA: a wide-field, multi-colour, high-speed photometer at the prime focus of the Hale telescope

The Caltech HIgh-speed Multi-color camERA (CHIMERA) is a new instrument that has been developed for use at the prime focus of the Hale 200-inch telescope. Simultaneous optical imaging in two bands is enabled by a dichroic beam splitter centered at 567 nm, with Sloan u' and g' bands available on the blue arm and Sloan r', i' and z_s' bands available on the red arm. Additional narrow-band filters will also become available as required. An Electron Multiplying CCD (EMCCD) detector is employed for both optical channels, each capable of simultaneously delivering sub-electron effective read noise under multiplication gain and frame rates of up to 26 fps full frame (several 1000 fps windowed), over a fully corrected 5 x 5 arcmin field of view. CHIMERA was primarily developed to enable the characterization of the size distribution of sub-km Kuiper Belt Objects via stellar occultation, a science case that motivates the frame-rate, the simultaneous multi-color imaging and the wide field of view of the instrument. In addition, it also has unique capability in the detection of faint near-Earth asteroids and will be used for the monitoring of short duration transient and periodic sources, particularly those discovered by the intermediate Palomar Transient Factory (iPTF), and the upcoming Zwicky Transient Facility (ZTF).

Prototype of solar ground layer adaptive optics at the 1 m New Vacuum Solar Telescope

A prototype of a solar ground-layer adaptive optics (GLAO) system, which consists of a multi-direction correlating Shack–Hartmann wavefront sensor with 30 effective subapertures and about a 1 arcmin field of view (FoV) in each subaperture, a deformable mirror with 151 actuators conjugated to the telescope entrance pupil, and a custom-built real-time controller based on field-programmable gate array and multi-core digital signal processor (DSP), is implemented at the 1 m New Vacuum Solar Telescope at Fuxian Solar Observatory and saw its first light on January 12th, 2016. The on-sky observational results show that the solar image is apparently improved in the whole FoV over 1 arcmin with the GLAO correction.

Double-wedged Wollaston-type polarimeter design and integration to RTT150-TFOSC; initial tests, calibration, and characteristics

Photometric and spectroscopic observation capabilities of 1.5-m Russian–Turkish Telescope RTT150 has been broadened with the integration of presented polarimeter. The well-known double-wedged Wollaston-type dual-beam technique was preferred and applied to design and produce it. The designed polarimeter was integrated into the telescope detector TFOSC, and called TFOSC-WP. Its capabilities and limitations were attempted to be determined by a number of observation sets. Non-polarized and strongly polarized stars were observed to determine its limitations as well as its linearity. An instrumental intrinsic polarization was determined for the 1 × 5 arcmin field of view in equatorial coordinate system, the systematic error of polarization degree as 0.2 %, and position angle as 1.9∘. These limitations and capabilities are denoted as good enough to satisfy telescopes’ present and future astrophysical space missions related to GAIA and SRG projects.

First observation of the thermal Sunyaev-Zel’dovich effect with kinetic inductance detectors

Clusters of galaxies provide valuable information on the evolution of the Universe and large scale structures. Recent cluster observations via the thermal Sunyaev-Zel'dovich (tSZ) effect have proven to be a powerful tool to detect and study them. In this context, high resolution tSZ observations (~ tens of arcsec) are of particular interest to probe intermediate and high redshift clusters. Observations of the tSZ effect will be carried out with the millimeter dual-band NIKA2 camera, based on Kinetic Inductance Detectors (KIDs) to be installed at the IRAM 30-meter telescope in 2015. To demonstrate the potential of such an instrument, we present tSZ observations with the NIKA camera prototype, consisting of two arrays of 132 and 224 detectors that observe at 140 and 240 GHz with a 18.5 and 12.5 arcsec angular resolution, respectively. The cluster RX J1347.5-1145 was observed simultaneously at 140 and 240 GHz. We used a spectral decorrelation technique to remove the atmospheric noise and obtain a map of the cluster at 140 GHz. The efficiency of this procedure has been characterized through realistic simulations of the observations. The observed 140 GHz map presents a decrement at the cluster position consistent with the tSZ nature of the signal. We used this map to study the pressure distribution of the cluster by fitting a gNFW model to the data. Subtracting this model from the map, we confirm that RX J1347.5-1145 is an ongoing merger, which confirms and complements previous tSZ and X-ray observations. For the first time, we demonstrate the tSZ capability of KID based instruments. The NIKA2 camera with ~ 5000 detectors and a 6.5 arcmin field of view will be well-suited for in-depth studies of the intra cluster medium in intermediate to high redshifts, which enables the characterization of recently detected clusters by the Planck satellite.

Cosmic flows: University of Hawaii 2.2-m I-band photometry

Within the "Cosmic Flows" project, I-band photometry of 524 relatively nearby galaxies has been carried out over the course of several years with the University of Hawaii 2.2m telescope and a camera with a 7.5 arcmin field of view. The primary scientific purpose was to provide global magnitudes and inclinations for galaxies for the purpose of measuring distances through the correlation between galaxy luminosities and rotation rates. The accuracy on a total magnitude is 0.08 mag. The observations typically extend to 7-8 exponential disk scalelengths so the data are useful for studies of the structural properties of galaxies.

A MAD view of Trumpler 14

We present adaptive optics (AO) near-infrared observations of the core of the Tr 14 cluster in the Carina region obtained with the ESO multi-conjugate AO demonstrator, MAD. Our campaign yields AO-corrected observations with an image quality of about 0.2 arcsec across the 2 arcmin field of view, which is the widest AO mosaic ever obtained. We detected almost 2000 sources spanning a dynamic range of 10 mag. The pre-main sequence (PMS) locus in the colour-magnitude diagram is well reproduced by Palla & Stahler isochrones with an age of 3 to 5 1E+05 yr, confirming the very young age of the cluster. We derive a very high (deprojected) central density n0~4.5(+/-0.5) \times 10^4 pc^-3 and estimate the total mass of the cluster to be about ~4.3^{+3.3}_{-1.5} \times 10^3 Msun, although contamination of the field of view might have a significant impact on the derived mass. We show that the pairing process is largely dominated by chance alignment so that physical pairs are difficult to disentangle from spurious ones based on our single epoch observation. Yet, we identify 150 likely bound pairs, 30% of these with a separation smaller than 0.5 arcsec (~1300AU). We further show that at the 2-sigma level massive stars have more companions than lower-mass stars and that those companions are respectively brighter on average, thus more massive. Finally, we find some hints of mass segregation for stars heavier than about 10 Msun. If confirmed, the observed degree of mass segregation could be explained by dynamical evolution, despite the young age of the cluster.

STUDIES OF MILLIMETER-WAVE ATMOSPHERIC NOISE ABOVE MAUNA KEA

We report measurements of the fluctuations in atmospheric emission (atmospheric noise) above Mauna Kea recorded with Bolocam at 143 and 268 GHz from the Caltech Submillimeter Observatory (CSO). The 143 GHz data were collected during a 40 night observing run in late 2003, and the 268 GHz observations were made in early 2004 and early 2005 over a total of 60 nights. Below 0.5 Hz, the data time-streams are dominated by atmospheric noise in all observing conditions. The atmospheric noise data are consistent with a Kolmogorov-Taylor (K-T) turbulence model for a thin wind-driven screen, and the median amplitude of the fluctuations is 280 mK^2 rad^(-5/3) at 143 GHz and 4000 mK^2 rad^(-5/3) at 268 GHz. Comparing our results with previous ACBAR data, we find that the normalization of the power spectrum of the atmospheric noise fluctuations is a factor of 80 larger above Mauna Kea than above the South Pole at millimeter wavelengths. Most of this difference is due to the fact that the atmosphere above the South Pole is much drier than the atmosphere above Mauna Kea. However, the atmosphere above the South Pole is slightly more stable as well: the fractional fluctuations in the column depth of precipitable water vapor are a factor of sqrt(2) smaller at the South Pole compared to Mauna Kea. Based on our atmospheric modeling, we developed several algorithms to remove the atmospheric noise, and the best results were achieved when we described the fluctuations using a low-order polynomial in detector position over the 8 arcmin field of view (FOV). However, even with these algorithms, we were not able to reach photon-background-limited instrument photometer (BLIP) performance at frequencies below 0.5 Hz in any observing conditions.

An adaptive 2 m class telescope for a microlensing search from Antarctica

We describe the scientific rationale and the preliminary optomechanical design for a 2 m class telescope designed to achieve ground layer correction over a ≈ 15 arcmin Field of View (FoV) to be located at the Dome-C site. The proposed science case is the detection of microlensing events in and by globular clusters and nearby galaxies that, for a high probability of success, requires exceptional seeing ( ≈ 0.2 arcsec or better) and a large target density (the centre of a globular cluster with a corresponding telescope FoV of ≈ 15 arcmin). This approach can capitalise on some of the unique qualities already observed above the Dome-C site, namely that the atmospheric turbulence is largely limited to a ground layer of small thickness only, a relatively low Greenwood frequency and uniterrupted sky coverage during the winter months for objects such as the globular cluster 47-Tuc. Further to the central science case of microlensing the telescope could provide a technological testbed for future telescopes and, given the unique atmospheric properties witnessed already during previous site testing compaigns, has the chance to provide a large amount of data (based on accurate and continuous light curves lasting several months) for fields of research outside that of microlensing. Details of the specific concepts of adaptive optics to be adopted for this telescope are outlined.

SCUBA-2: A large-format TES array for submillimetre astronomy

SCUBA-2, which replaces the Submillimetre Common User Bolometer Array (SCUBA) (Mon. Not. R. Astron. Soc. 303 (1999) 659) on the James Clerk Maxwell telescope in 2006, will be the first CCD-like array for submillimeter astronomy. Unlike previous detectors which have used discrete bolometers, SCUBA-2 has two DC-coupled, monolithic, filled arrays with a total of ∼10,000 bolometers. It will offer simultaneous imaging of an 8×8 arcmin field of view at wavelengths of 850 and 450μm. SCUBA-2 is expected to have a huge impact on the study of galaxy formation and evolution in the early Universe as well as star and planet formation in our own Galaxy. Mapping the sky to the same S/N up to 1000 times faster than SCUBA, it will also act as a pathfinder for the new submillimetre interferometers such as ALMA. SCUBA-2's absorber-coupled pixels use superconducting transition edge sensors (Ph.D. Thesis, Stanford, 1995) operating at ∼120mK for photon noise limited performance. The monolithic silicon detector arrays are deep-etched by the Bosch process to isolate the pixels on silicon nitride membranes (Nucl. Instr. and Meth. A, these proceedings). Electrical connections are made through indium bump bonds to a backplane that incorporates a SQUID time-domain multiplexer. We describe the key technologies that make SCUBA-2 possible and give an update on the considerable progress in the detector development and instrument design that has taken place over the last 2 years.

Total-light imager with flat spectral response for solar photometric measurements

Certain applications in imaging photometry and radiometry require a telescope-detector system with (preferably constant) response over a wide spectral range from the ultraviolet through the infrared. We describe the design and characterization of the Solar Bolometric Imager (SBI), a 30-cm-aperture Dall-Kirkham telescope combined with a gold-blacked, 80, 000-element thermal array detector. Our SBI prototype provides spectrally uniform imaging in total solar light (0.28-2.6 mum) of heat-flow inhomogeneities at the solar photosphere, with better than 5-arc sec angular resolution over a 6.5 x 13 arc min field of view. A balloon-borne SBI would avoid most atmospheric transmission variation over this spectral range, enabling accurate study of the sources of total irradiance variation.

Off-axis systems for 4-m class telescopes

We describe here an off-axis design for a 4.0-m astronomical telescope. We show that the geometric optical performance of this configuration can equal that of an on-axis conventional configuration while the diffractive performance fundamentally surpasses conventional telescopes because of the absence of pupil obstruction. The specific optical design described here uses a single off-axis primary mirror to obtain three distinct final focus ports: an f/10 port (with corrector) for wide-field imaging and spectroscopy with a field of view (FOV) of 15 arc min; a small-field, 2-reflection f/10 port suitable for polarimetry and coronagraphy; and a slower, f/16(3-reflection) port with a 7 arc min FOV. For general astronomical observations requiring high optical throughput and low scattered light, this design is superior to conventional Ritchey-Chretien optical configurations.

EIT OBSERVATIONS OF THE EXTREME ULTRAVIOLET SUN

The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 × 45 arc min field of view in four emission line groups: Fe IX, X, Fe XIIi, Fe xv, and He II. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops.

Optical signatures of high-redshift galaxy clusters

We combine an N-body and gasdynamic simulation of structure formation with an updated population synthesis code to explore the expected optical characteristics of a high-redshift cluster of galaxies. We examine a poor (2 keV) cluster formed in a biased, cold dark matter cosmology and employ simple, but plausible, threshold criteria to convert gas into stars. At z = 2, the forming cluster appears as a linear chain of very blue (g - r~0) galaxies, with 15 objects brighter than r = 25 within a 1 square arcmin field of view. After 2 Gyr of evolution, the cluster viewed at z = 1 displays both freshly infalling blue galaxies and red galaxies robbed of recent accretion by interaction with the hot intracluster medium. The range in G - R colors is ~3 mag at z = 1, with the reddest objects lying at sites of highest galaxy density. We suggest that red, high-redshift galaxies lie in the cores of forming clusters and that their existence indicates the presence of a hot intracluster medium at redshifts z~2. The simulated cluster viewed at z = 2 has several characteristics similar to the collection of faint, blue objects identified by Dressler et al. in a deep Hubble Space Telescope observation. The similarities provide some support for the interpretation of this collection as a high- redshift cluster of galaxies.