Simultaneous Wavelength Coverage Research Articles

The Science Performance of the Gemini High Resolution Optical Spectrograph

The Gemini High Resolution Optical Spectrograph (GHOST) is a fiber-fed spectrograph system on the Gemini South telescope that provides simultaneous wavelength coverage from 348 to 1061 nm, and is designed for optimal performance between 363 and 950 nm. It can observe up to two objects simultaneously in a 7.′5 diameter field of regard at R ≃ 56,000 or a single object at R ≃ 75,000. The spectral resolution modes are obtained by using integral field units to image slice a 1.″2 aperture by a factor of five in width using 19 fibers in the high resolution mode and by a factor of three in width using 7 fibers in the standard resolution mode. GHOST is equipped with hardware to allow for precision radial velocity measurements, expected to approach meters per second precision. Here, we describe the basic design and operational capabilities of GHOST, and proceed to derive and quantify the key aspects of its on-sky performance that are of most relevance to its science users.

The Near Infrared Imager and Slitless Spectrograph for the James Webb Space Telescope. I. Instrument Overview and In-flight Performance

The Near-Infrared Imager and Slitless Spectrograph (NIRISS) is the science module of the Canadian-built Fine Guidance Sensor onboard the James Webb Space Telescope (JWST). NIRISS has four observing modes: (1) broadband imaging featuring seven of the eight NIRCam broadband filters, (2) wide-field slitless spectroscopy at a resolving power of ∼150 between 0.8 and 2.2 μm, (3) single-object cross-dispersed slitless spectroscopy (SOSS) enabling simultaneous wavelength coverage between 0.6 and 2.8 μm at R ∼ 700, a mode optimized for exoplanet spectroscopy of relatively bright (J < 6.3) stars and (4) aperture masking interferometry (AMI) between 2.8 and 4.8 μm enabling high-contrast (∼10−3 − 10−4) imaging at angular separations between 70 and 400 mas for relatively bright (M < 8) sources. This paper presents an overview of the NIRISS instrument, its design, its scientific capabilities, and a summary of in-flight performance. NIRISS shows significantly better response shortward of ∼2.5 μm resulting in 10%–40% sensitivity improvement for broadband and low-resolution spectroscopy compared to pre-flight predictions. Two time-series observations performed during instrument commissioning in the SOSS mode yield very stable spectro-photometry performance within ∼10% of the expected noise. The first space-based companion detection of the tight binary star AB Dor AC through AMI was demonstrated.

PyTANSPEC: A data reduction package for TANSPEC

TIFR-ARIES Near Infrared Spectrometer (TANSPEC) instrument provides simultaneous wavelength coverage from 0.55 to 2.5 $$\mu $$ m, mounted on India’s largest ground-based telescope, 3.6-m Devasthal Optical Telescope at Nainital, India. The TANSPEC offers three modes of observations, imaging with various filters, spectroscopy in the low-resolution prism mode with derived $$R\sim 100$$ –400 and the high-resolution cross-dispersed mode (XD-mode) with derived median $$R\sim 2750$$ for a slit of width 0.5 arcsec. In the XD-mode, 10 cross-dispersed orders are packed in the $$2048 \times 2048$$ pixels detector to cover the full wavelength regime. As the XD-mode is most utilized as well as for consistent data reduction for all orders and to reduce data reduction time, a dedicated pipeline is essential. In this paper, we present the code for the TANSPEC XD-mode data reduction, its workflow, input/output files and a showcase of its implementation on a particular dataset. This publicly available pipeline pyTANSPEC is fully developed in Python and includes nominal human intervention only for the quality assurance of the reduced data. Two customized configuration files are used to guide the data reduction. The pipeline creates a log file for all the fit files in a given data directory from its header, identifies correct frames (science, continuum and calibration lamps) based upon the user input, offers an option to the user for eyeballing and accepting/removing of the frames, does the cleaning of raw science frames and yields final wavelength calibrated spectra of all orders simultaneously.

MIRECLE: Science Yield for a Mid-infrared Explorer-class Mission to Study Nontransiting Rocky Planets Orbiting the Nearest M Stars Using Planetary Infrared Excess

Recent investigations have demonstrated the potential for utilizing a new observational and data-analysis technique for studying the atmospheres of nontransiting exoplanets with combined light that relies on acquiring simultaneous, broad-wavelength spectra and resolving planetary infrared emission from the stellar spectrum through simultaneous fitting of the stellar and planetary spectral signatures. This new data-analysis technique, called planetary infrared excess (PIE), holds the potential to open up the opportunity for measuring mid-infrared (MIR) phase curves of nontransiting rocky planets around the nearest stars with a relatively modest telescope aperture. We present simulations of the performance and science yield for a mission and instrument concept that we call the MIR Exoplanet CLimate Explorer, a concept for a moderately sized cryogenic telescope with broad wavelength coverage (1–18 μm) and a low-resolution (R ∼ 50) spectrograph designed for the simultaneous wavelength coverage and extreme flux measurement precision necessary to detect the emission from cool rocky planets with PIE. We present exploratory simulations of the potential science yield for PIE measurements of the nearby planet Proxima Centauri b, showing the potential to measure the composition and structure of an Earth-like atmosphere with a relatively modest observing time. We also present overall science yields for several mission architecture and performance metrics, and discuss the technical performance requirements and potential telescope and instrument technologies that could meet these requirements.

Where Is the Water? Jupiter-like C/H Ratio but Strong H2O Depletion Found on τ Boötis b Using SPIRou

Abstract The present-day envelope of gaseous planets is a relic of how these giant planets originated and evolved. Measuring their elemental composition therefore presents a powerful opportunity to answer long-standing questions regarding planet formation. Obtaining precise observational constraints on the elemental inventory of giant exoplanets has, however, remained challenging owing to the limited simultaneous wavelength coverage of current space-based instruments. Here, we present thermal emission observations of the nontransiting hot Jupiter τ Boo b using the new wide wavelength coverage (0.95–2.50 μm) and high spectral resolution (R = 70,000) CFHT/SPIRou spectrograph. By combining a total of 20 hr of SPIRou data obtained over five nights in a full atmospheric retrieval framework designed for high-resolution data, we constrain the abundances of all the major oxygen- and carbon-bearing molecules and recover a noninverted temperature structure using a new free-shape, nonparametric temperature–pressure profile retrieval approach. We find a volume mixing ratio of log(CO) = − 2.46 − 0.29 + 0.25 and a highly depleted water abundance of less than 0.0072 times the expected value for a solar composition envelope. Combined with upper limits on the abundances of CH4, CO2, HCN, TiO, and C2H2, this results in a gas-phase C/H ratio of 5.85 − 2.82 + 4.44 × solar, consistent with the value of Jupiter, and an envelope C/O ratio robustly greater than 0.60, even when taking into account the oxygen that may be sequestered out of the gas phase. Combined, the inferred supersolar C/H, O/H, and C/O ratios on τ Boo b support a formation scenario beyond the water snowline in a disk enriched in CO owing to pebble drift.

Gemini Observations of Galaxies in Rich Early Environments (GOGREEN) I: survey description

We describe a new Large Program in progress on the Gemini North and South telescopes: Gemini Observations of Galaxies in Rich Early Environments (GOGREEN). This is an imaging and deep spectroscopic survey of 21 galaxy systems at $1<z<1.5$, selected to span a factor $>10$ in halo mass. The scientific objectives include measuring the role of environment in the evolution of low-mass galaxies, and measuring the dynamics and stellar contents of their host haloes. The targets are selected from the SpARCS, SPT, COSMOS and SXDS surveys, to be the evolutionary counterparts of today's clusters and groups. The new red-sensitive Hamamatsu detectors on GMOS, coupled with the nod-and-shuffle sky subtraction, allow simultaneous wavelength coverage over $\lambda\sim 0.6$--$1.05\mu$m, and this enables a homogeneous and statistically complete redshift survey of galaxies of all types. The spectroscopic sample targets galaxies with AB magnitudes $z^{\prime}<24.25$ and [3.6]$\mu$m$<22.5$, and is therefore statistically complete for stellar masses $M_\ast\gtrsim10^{10.3}M_\odot$, for all galaxy types and over the entire redshift range. Deep, multiwavelength imaging has been acquired over larger fields for most systems, spanning $u$ through $K$, in addition to deep IRAC imaging at 3.6$\mu$m. The spectroscopy is $\sim 50$ per cent complete as of semester 17A, and we anticipate a final sample of $\sim 500$ new cluster members. Combined with existing spectroscopy on the brighter galaxies from GCLASS, SPT and other sources, GOGREEN will be a large legacy cluster and field galaxy sample at this redshift that spectroscopically covers a wide range in stellar mass, halo mass, and clustercentric radius.

OVERVIEW OF THE SDSS-IV MaNGA SURVEY: MAPPING NEARBY GALAXIES AT APACHE POINT OBSERVATORY

We present an overview of a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), one of three core programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV) that began on 2014 July 1. MaNGA will investigate the internal kinematic structure and composition of gas and stars in an unprecedented sample of 10,000 nearby galaxies. We summarize essential characteristics of the instrument and survey design in the context of MaNGA's key science goals and present prototype observations to demonstrate MaNGA's scientific potential. MaNGA employs dithered observations with 17 fiber-bundle integral field units that vary in diameter from 12" (19 fibers) to 32" (127 fibers). Two dual-channel spectrographs provide simultaneous wavelength coverage over 3600-10300 A at R~2000. With a typical integration time of 3 hr, MaNGA reaches a target r-band signal-to-noise ratio of 4-8 (per A, per 2" fiber) at 23 AB mag per sq. arcsec, which is typical for the outskirts of MaNGA galaxies. Targets are selected with stellar mass greater than 1e9 Msun using SDSS-I redshifts and i-band luminosity to achieve uniform radial coverage in terms of the effective radius, an approximately flat distribution in stellar mass, and a sample spanning a wide range of environments. Analysis of our prototype observations demonstrates MaNGA's ability to probe gas ionization, shed light on recent star formation and quenching, enable dynamical modeling, decompose constituent components, and map the composition of stellar populations. MaNGA's spatially resolved spectra will enable an unprecedented study of the astrophysics of nearby galaxies in the coming 6 yr.

ACCRETION RATES FOR T TAURI STARS USING NEARLY SIMULTANEOUS ULTRAVIOLET AND OPTICAL SPECTRA

We analyze the accretion properties of 21 low mass T Tauri stars using a dataset of contemporaneous near ultraviolet (NUV) through optical observations obtained with the Hubble Space Telescope Imaging Spectrograph (STIS) and the ground based Small and Medium Aperture Research Telescope System (SMARTS), a unique dataset because of the nearly simultaneous broad wavelength coverage. Our dataset includes accreting T Tauri stars (CTTS) in Taurus, Chamaeleon I, $\eta$ Chamaeleon and the TW Hydra Association. For each source we calculate the accretion rate by fitting the NUV and optical excesses above the photosphere, produced in the accretion shock, introducing multiple accretion components characterized by a range in energy flux (or density) for the first time. This treatment is motivated by models of the magnetospheric geometry and accretion footprints, which predict that high density, low filling factor accretion spots co-exist with low density, high filling factor spots. By fitting the UV and optical spectra with multiple accretion components, we can explain excesses which have been observed in the near infrared. Comparing our estimates of the accretion rate to previous estimates, we find some discrepancies; however, they may be accounted for when considering assumptions for the amount of extinction and variability in optical spectra. Therefore, we confirm many previous estimates of the accretion rate. Finally, we measure emission line luminosities from the same spectra used for the accretion rate estimates, to produce correlations between accretion indicators (H$\beta$, Ca II K, C II] and Mg II) and accretion properties obtained simultaneously.

Use of a High-Resolution Overview Spectrometer for the Visible Range in the TEXTOR Boundary Plasma

Passive spectroscopy is a standard diagnostic to observe the boundary layer of fusion plasmas. This method of visible spectroscopy is focused on the measurement of deuterium recycling flux and on the monitoring of impurity fluxes of O, He, etc., or W, C, etc., which result from erosion of plasma-facing components. In addition, ro-vibrational analysis of molecular transitions provides information about the molecular break-up in the plasma. Spectrometers used for studying the plasma boundary have to fulfill high demands with respect to the spectral, spatial, and time resolutions, the observable wavelength range, to the sensitivity and dynamic range of the detector in order to simultaneously observe and analyze the emission of both, atomic and molecular species present in the observed region. We present an overview spectrometer system that is able (a) to simultaneously measure strong atomic lines (e.g. Dα) and weak molecular bands (e.g. C2 Swan band), (b) to resolve narrow molecular lines (e.g. D2 Fulcher-α band) and allow their ro-vibrational analysis, and (c) to provide information about the spatial distribution in the plasma boundary. A full characterization of the custom-made system in a cross-dispersion arrangement with respect to resolving power, simultaneous wavelength coverage, sensitivity, etc., is presented. Examples of spectra (“footprints”) taken from an injection of C3H4 into TEXTOR are presented.

Gemini Near-Infrared Spectroscopy of Luminousz~ 6 Quasars: Chemical Abundances, Black Hole Masses, and MgiiAbsorption

We present Gemini near-infrared spectroscopic observations of six luminous quasars at z = 5.8 to ∼6.3. Five of them were observed using Gemini South GNIRS, which provides a simultaneous wavelength coverage of 0.9-2.5 μm in cross-dispersion mode. The other source was observed in the K band with Gemini North NIRI. We calculate line strengths for all detected emission lines and use their ratios to estimate gas metallicity in the broad-line regions of the quasars. The metallicity is found to be supersolar, with a typical value of ∼4 Z⊙, and a comparison with low-redshift observations shows no strong evolution in metallicity up to z ∼ 6. The Fe II/Mg II ratio of the quasars is 4.9 ± 1.4, consistent with low-redshift measurements. We estimate central black hole masses of 109-1010 M⊙ and Eddington luminosity ratios of order unity. We identify two Mg II λλ2796, 2803 absorbers with rest equivalent width W > 1 Å at 2.2 < z < 3 and three Mg II absorbers with W > 1.5 Å at z > 3 in the spectra, with the two most distant absorbers at z = 4.8668 and 4.8823, respectively. The redshift number densities (dN/dz) of Mg II absorbers with W > 1.5 Å are consistent with no cosmic evolution up to z > 4.

REM/ROSS: a powerful tool for monitoring the prompt afterglow of γ-ray bursts

Observations of the prompt afterglow of γ-ray burst events are unanimously considered of paramount importance for GRB science and cosmology. Such observations at NIR wavelengths are even more promising allowing the monitoring of high- z Ly-α absorbed bursts as well as events occurring in dusty star-forming regions. In these pages we present rapid eye mount (REM), a fully robotized fast slewing telescope equipped with a high throughput NIR (Z, J, H, K) camera dedicated to detecting the prompt IR afterglow. REM can discover objects at extremely high redshift and trigger large telescopes to observe them. The REM telescope will simultaneously feed REM optical slitless spectrograph (ROSS) via a dichroic. ROSS will intensively monitor the prompt optical continuum of GRB afterglows. The synergy between the REM-IR camera and the ROSS spectrograph makes REM a powerful observing tool for any kind of fast transient phenomena. Beside its ambitious scientific goals, REM is also technically challenging since it represent the first attempt to locate a NIR camera on a small telescope providing, with ROSS, unprecedented simultaneous wavelength coverage on a telescope of this size.

Spectroscopy of T Tauri stars with UVES

We present the first results of our observations of classical T Tauri Stars with UVES/VLT. The data consists of high signal-to-noise (150) and high spectral resolution (R 60 000) spectra. A large simultaneous wavelength coverage throughout most of the visible spectrum and comparatively short integration times allow us to study variability on short time-scales, using a number of diagnostics reflecting a wide range of physical processes. In particular we concentrate on the properties and geometry of the accretion process in the strongly accreting and highly variable CTTS RU Lup. We use the evolution of the level of veiling, the shapes of absorption and emission lines, and correlations between these diagnostics, to make new measurements of the fundamental stellar parameters as well as constraints on the accretion process and its geometry. We also derive the shortest time-scale of incoherent changes, which has implications for the nature of the accretion process in RU Lup. Since their discovery one of the most intriguing properties of the classical T Tauri stars (CTTS) has been their apparently chaotic variability visible with nearly all observational tech- niques, from broad-band photometry to high-resolution spec- troscopy. The spectra of these low-mass pre-main sequence objects are densely populated with emission lines including hydrogen, permitted and forbidden metallic lines and lines of helium (for a complete compilation of observational proper- ties see e.g. Bertout 1989). The CTTS phase in the evolution of low-mass stars is rather short - a few million years. In the same age interval one finds, apart from CTTS, a group of weak line T Tauri stars (WTTS), with very weak or absent emission spectra. The characteristic properties of CTTS are attributed to the presence of an accretion disk while WTTS apparently lack such a disk. Whether there exists an evolutionary connection between the two groups is still unclear. CTTS represent a real challenge for both modelling and ob- servations. In this paper we will concentrate on the observa- tional signatures of CTTS, on their variability and the plausible connection to the accretion processes. The observational picture of CTTS is very complex. Photometry reveals a high level of variability on timescales from minutes to years with changes in brightness by a factor of two or more. CTTS show an excess of radiation in the IR

Extended optical spectroscopic monitoring of wind structure in HD 152408

New perspectives are provided on signicant spatial structure and temporal variability in the near- star wind regions (i.e. < 3 R?) of the massive luminous star HD 152408 (classied as O8:Iafpe or WN9ha). This study is primarily based on the analysis of high-quality echelle spectra secured during 21 nights between 1999 July to August, using the Landessternwarte-developed (bre-fed) FEROS instrument on the ESO 1.52-m telescope. These extended time-series data, with a total simultaneous wavelength coverage of 3600 9200 A, were exploited to monitor absorption and emission fluctuations (of5{10% of the line flux) in several He i and Balmer lines, together with more deep-seated (near-photosphere) disturbances in weaker metallic emission and absorption lines. Organised large-scale wind structure in HD 152408 is principally betrayed by sequential episodes of discrete absorption and emission features, which migrate from near zero velocity to almost the wind terminal velocity. This evolution is extremely slow, however, typically spanning 4 days for an individual episode. We demonstrate that the blue-shifted absorption episodes in He i are very closely mirrored (in velocity and time) by absorption features (i.e. reduced not enhanced flux) in the blue wings of the mainly recombination formed broad H emission line. The implication is that there is detailed balancing between ground state photoionization and recombination in the substantially optically thick Balmer lines. Surprisingly, the velocity behaviour of the red-ward and blue-ward migrating features is highly asymmetric, such that the mean acceleration of the former is less than 50% of the latter. Fourier analysis reveals a modulation time-scale for the wind activity of7.7 days, plus its harmonic at 3.9 days. The longer period is28 times greater than the characteristic radial wind flow time of HD 152408. We also detect a1.5 day periodic variation in the radial velocity of the weak C iv 5801, 5812 absorption lines, which are the closest approximation to \pure photospheric lines in the optical spectrum of HD 152408. The wind-formed optical lines of HD 152408 are also aected by fluctuations in the central peak emission, particularly evident in H where the equivalent width may vary by up to 20%. Data secured between 1995 and 1999 reveal, however, that the epoch-to-epoch mean proles are remarkably similar. Non-LTE steady- state stellar atmosphere models are used to synthesis proles to match representative H and He i 5876 line proles. Only a slow (tailored) velocity law (compared to =1 ) provides ag ood match to the H emission peak and wings, but the models predict excess He i absorption. The observed extreme H emission variations can be reproduced by the synthetic proles with an implied 10% variation in mass-loss rate. The results on optical line prole variability in HD 152408 are discussed in the context of models for co-rotating interaction regions (CIRs) in the wind. Several constraints are provided that argue against simple velocity elds in such streams, including (i) the slow acceleration of features to high velocities, within3 R?, (ii) the strong asymmetry in projected acceleration of the approaching and receding stream material, (iii) Balmer line absorption eects in the approaching material, (iv) the rise of localised features from very low velocities, and (v) the stability of the large-scale CIRs against turbulent small-scale wind structure. We suggest that it may be worth exploring hydrodynamic simulations of CIRs that incorporate dierent velocity elds on the leading (faster accelerating; blue-ward absorption) and trailing (slower accelerating; red-ward emission) edges of the spiral structures.