High-resolution Near-infrared Spectroscopy Research Articles

IN-SYNC. IV. THE YOUNG STELLAR POPULATION IN THE ORION A MOLECULAR CLOUD

ABSTRACT We present the results of the Sloan Digital Sky Survey APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC) survey of the Orion A molecular cloud. This survey obtained high-resolution near-infrared spectroscopy of about 2700 young pre-main-sequence stars on a ∼ 6 ° ?> field of view. We have measured accurate stellar parameters ( T eff ?> , log g ?> , v sin i ?> ) and extinctions and placed the sources in the Hertzsprung–Russel diagram (HRD). We have also extracted radial velocities for the kinematic characterization of the population. We compare our measurements with literature results to assess the performance and accuracy of the survey. Source extinction shows evidence for dust grains that are larger than those in the diffuse interstellar medium: we estimate an average R V = 5.5 in the region. Importantly, we find a clear correlation between HRD inferred ages and spectroscopic surface-gravity-inferred ages and between extinction and disk presence; this strongly suggests a real spread of ages larger than a few Myr. Focusing on the young population around NGC 1980/ι Ori, which has previously been suggested to be a separate, foreground, older cluster, we confirm its older (∼5 Myr) age and low A V , but considering that its radial velocity distribution is indistinguishable from Orion A’s population, we suggest that NGC 1980 is part of Orion A’s star formation activity. Based on their stellar parameters and kinematic properties, we identify 383 new candidate members of Orion A, most of which are diskless sources in areas of the region poorly studied by previous works.

INFRARED ABSORPTION LINES TOWARD NGC 7538 IRS 1: ABUNDANCES OF H2, H3+, AND CO

We report high-resolution near-infrared absorption spectroscopy of H2, H3+, and CO toward the young high mass object NGC 7538 IRS 1. The v = 1–0 H2 S(0) line and lines in the CO v = 2–0 band were detected; the v = 1–0 H2 S(1) line and the v = 1–0 H3+ lines [R(1, 1)l, R(1, 0), R(1, 1)u] were not detected. The line of sight traverses two clouds, with temperatures 45 and 259 K and with roughly equal column densities of CO. Assuming that H2 is at the same temperature as CO and that the two species are uniformly mixed, [H2]/[CO] = 3600 ± 1200. NGC 7538 is the most distant object from the Galactic center for which [H2]/[CO] has been directly measured using infrared absorption spectroscopy.

High-Resolution Near-Infrared Spectroscopy of CH2+ and Its Deuterated Isotopologues

Aiming to provide approximate rotational constants for millimeter wave spectroscopists to identify the corresponding species in space, we have recorded the near-infrared spectra of the methylene cation CH2(+) and its deuterated isotopologues, CD2(+) and CHD+, using a high resolution and high sensitivity spectrometer. Detection of CH2(+) in space will shed light on interstellar chemistry as it is the intermediate between the abundant CH+ and yet to be observed CH3(+), which is important in the formation of larger organic molecules. CH2(+) and its deuterated isotopologues are also of special interest for theoretical studies because of their unique intramolecular dynamics, i.e., the Renner–Teller interaction and quasi-linearity. This paper will discuss several new bands of CH2(+), the Ã(0,5[11],0)0 ← X̃(0,0[0],0)1 and Ã(0,4[11],0)2 ← X̃(0,0[0],0)1 bands of CD2(+), which have been identified and analyzed, and the candidate lines for the Ã(0,4[10],0)1 ← X̃(0,0[1],0)0 band of CHD+, in comparison with the theoretical predictions by Bunker and colleagues.

DISCOVERY OF A VERY LOW MASS TRIPLE WITH LATE-M AND T DWARF COMPONENTS: LP 704-48/SDSS J0006–0852AB

We report the identification of the M9 dwarf SDSS J000649.16-085246.3 as a spectral binary and radial velocity variable with components straddling the hydrogen burning mass limit. Low-resolution near-infrared spectroscopy reveals spectral features indicative of a T dwarf companion, and spectral template fitting yields component types of M8.5\pm0.5 and T5\pm1. High-resolution near-infrared spectroscopy with Keck/NIRSPEC reveals pronounced radial velocity variations with a semi-amplitude of 8.2\pm0.4 km/s. From these we determine an orbital period of 147.6\pm1.5 days and eccentricity of 0.10\pm0.07, making SDSS J0006-0852AB the third tightest very low mass binary known. This system is also found to have a common proper motion companion, the inactive M7 dwarf LP 704-48, at a projected separation of 820\pm120 AU. The lack of H-alpha emission in both M dwarf components indicates that this system is relatively old, as confirmed by evolutionary model analysis of the tight binary. LP 704-48/SDSS J0006-0852AB is the lowest-mass confirmed triple identified to date, and one of only seven candidate and confirmed triples with total masses below 0.3 Msun currently known. We show that current star and brown dwarf formation models cannot produce triple systems like LP 704-48/SDSS J0006-0852AB, and we rule out Kozai-Lidov perturbations and tidal circularization as a viable mechanism to shrink the inner orbit. The similarities between this system and the recently uncovered low-mass eclipsing triples NLTT 41135AB/41136 and LHS 6343ABC suggest that substellar tertiaries may be common in wide M dwarf pairs.

DISCOVERY OF TWO L AND T BINARIES WITH WIDE SEPARATIONS AND PECULIAR PHOTOMETRIC PROPERTIES

We present spatially resolved photometric and spectroscopic observations of two wide brown dwarf binaries uncovered by the SIMP near-infrared proper motion survey. The first pair (SIMP J1619275+031350AB) has a separation of 0.691" (15.2 AU) and components T2.5+T4.0, at the cooler end of the ill-understood J-band brightening. The system is unusual in that the earlier-type primary is bluer in J-Ks than the later-type secondary, whereas the reverse is expected for binaries in the late-L to T dwarf range. This remarkable color reversal can possibly be explained by very different cloud properties between the two components. The second pair (SIMP J1501530-013506AB) consists of an L4.5+L5.5 (separation 0.96", 30-47 AU) with a surprisingly large flux ratio (Delta J =1.79 mag) considering the similar spectral types of its components. The large flux ratio could be explained if the primary is itself an equal-luminosity binary, which would make it one of the first known triple brown dwarf systems. Adaptive optics observations could not confirm this hypothesis, but it remains a likely one, which may be verified by high-resolution near-infrared spectroscopy. These two systems add to the handful of known brown dwarf binaries amenable to resolved spectroscopy without the aid of adaptive optics and constitute prime targets to test brown dwarf atmosphere models.

Age Determinations of Early-M Type Pre-Main Sequence Stars Using a High-Resolution Near-Infrared Spectroscopic Method

Abstract We present a method for determining the age of early-M type pre-main sequence (PMS) stars based on estimations of the surface gravity. The surface gravity was measured using high-resolution near-infrared K-band spectroscopy. The age of the PMS stars can be determined from the surface gravity, which correlates with the photospheric contraction. To estimate the surface gravity while avoiding veiling contamination, we developed a surface gravity indicator using equivalent width ratios (EWRs) of nearby absorption lines. We derived a relationship between the ratios of the Sc (22057.8 Å and 22071.3 Å) and Na (22062.4 Å and 22089.7 Å) absorption lines and the surface gravity by observing giants and main-sequence stars. The surface gravities of early-M type stars were determined with an accuracy of 0.1 in log$g$. The ages of target PMS stars were estimated within a factor of 1.5 by comparing the surface gravity with the evolution model of Baraffe et al. (1998, A&A, 337, 403). The ages of 4 PMS stars were estimated to be older than indicated by previous age determinations made using the photometric method. The EWR method allows estimating the age of PMS stars without contaminating the uncertainty of the distance, extinction, and veiling.

Airborne imaging and NIR spectroscopy of the ESA ATV spacecraft re-entry: instrument design and preliminary data description

As part of the ESA/NASA Automated Transfer Vehicle (ATV) re-entry mission, we deployed a system of five cameras for visible and near-infrared (NIR) imaging and spectroscopic observation. These instruments were mounted in NASA's DC-8 Airborne Laboratory flying over the South Pacific Ocean. The ATV re-entry occurred on 29 September 2008, at ∼13:30 UT, and was recorded at a viewing distance of approximately 400 km from the site of its fragmentation in the mesosphere. Our instruments included intensified monochrome charge coupled device (CCD) cameras for narrow-field tracking and wide-field visible spectroscopy of the re-entry, and an InGaAs camera fitted with a grism was used for high-resolution NIR spectroscopy. Examples of the acquired data sets are discussed and include detection of visible atomic line emissions, NIR molecular band emissions and tracking of small fragments during the late stages of re-entry. The ATV re-entry campaign data are the first comprehensive airborne measurements of spacecraft break-up and provide important validation and constraint for state-of-the-art re-entry break-up models.

An in-depth look at the lunar crater Copernicus: Exposed mineralogy by high-resolution near-infrared spectroscopy

Newly acquired, sequentially spaced, high-resolution near-infrared spectra across the central section of crater Copernicus’ interior have been analyzed using a range of complementary techniques and indexes. We have developed a new interpretative method based on a multiple stage normalization process that appears to both confirm and expand on previous mineralogical estimations and mapping. In broad terms, the interpreted distribution of the principle mafic species suggests an overall composition of surface materials dominated by calcium-poor pyroxenes and minor olivine but with notable exceptions: the southern rim displays strong ca-rich pyroxene absorption features and five other locations, the uppermost northern crater wall, opposite rim sections facing the crater floor, and the central peak Pk1 and at the foot of Pk3, show instead strong olivine signatures. We also propose impact glass an alternative interpretation to the source of the weak but widespread olivine-like spectral signature found in low-reflectance samples, since it probably represents a major regolith constituent and component in large craters such as Copernicus. The high quality and performance of the SIR-2 data allows for the detection of diagnostic key mineral species even when investigating spectral samples with very subdued absorption features, confirming the intrinsic high-quality value of the returned data.

GLIMPSE-CO1: the most massive intermediate-age stellar cluster in the Galaxy

The stellar cluster GLIMPSE-C01 is a dense stellar system located in the Galactic Plane. Though often referred to in the literature as an old globular cluster traversing the Galactic disk, previous observations do not rule out that it is an intermediate age (less than a few Gyr) disk-borne cluster. Here, we present high-resolution near-infrared spectroscopy of over 50 stars in the cluster. We find an average radial velocity is consistent with being part of the disk, and determine the cluster's dynamical mass to be (8 \pm 3)x10^4 Msun. Analysis of the cluster's M/L ratio, the location of the Red Clump, and an extremely high stellar density, all suggest an age of 400-800Myr for GLIMPSE-C01, much lower than for a typical globular cluster. This evidence therefore leads us to conclude that GLIMPSE-C01 is part of the disk population, and is the most massive Galactic intermediate-age cluster discovered to date.

The discovery of a very cool, very nearby brown dwarf in the Galactic plane

Abstract We report the discovery of a very cool, isolated brown dwarf, UGPS 0722−05, with the United Kingdom Infrared Telescope Deep Sky Survey (UKIDSS) Galactic Plane Survey. The near-infrared spectrum displays deeper H2O and CH4 troughs than the coolest known T dwarfs and an unidentified absorption feature at 1.275 μm. We provisionally classify the object as a T10 dwarf but note that it may in future come to be regarded as the first example of a new spectral type. The distance is measured by trigonometric parallax as d = 4.1+0.6−0.5 pc, making it the closest known isolated brown dwarf. With the aid of Spitzer/Infrared Array Camera (IRAC) we measure H − [4.5] = 4.71. It is the coolest brown dwarf presently known – the only known T dwarf that is redder in H−[4.5] is the peculiar T7.5 dwarf SDSS J1416+13B, which is thought to be warmer and more luminous than UGPS 0722−05. Our measurement of the luminosity, aided by Gemini/T-ReCS N-band photometry, is L = 9.2 ± 3.1 × 10−7 L⊙. Using a comparison with well-studied T8.5 and T9 dwarfs we deduce Teff = 520 ± 40 K. This is supported by predictions of the Saumon & Marley models. With apparent magnitude J = 16.52, UGPS 0722−05 is the brightest of the ∼90 T dwarfs discovered by UKIDSS so far. It offers opportunities for future study via high-resolution near-infrared spectroscopy and spectroscopy in the thermal infrared.

GC-IRS13E—A PUZZLING ASSOCIATION OF THREE EARLY-TYPE STARS

We present a detailed analysis of high-resolution near-infrared imaging and spectroscopy of the potential star cluster IRS13E very close to the massive black hole in the Galactic center. We detect 19 objects in IRS13E from Ks-band images, 15 of which are also detected reliably in the H band. We derive consistent proper motions for these objects from the two bands. Most objects share a similar westward proper motion. We characterize the objects using spectroscopy (1.45–2.45 μm) and (narrowband) imaging from the H (1.66 μm) to the L' band (3.80 μm). Nine of the objects detected in both the Ks and H bands are very red, and we find that they are all consistent with being warm dust clumps. The dust emission may be caused by the colliding winds of the two Wolf-Rayet stars in the cluster. Three of the six detected stars do not share the motion or spectral properties of the three bright stars. This leaves only the three bright, early-type stars as potential cluster members. It is unlikely that these stars are a chance configuration. Assuming the presence of an intermediate mass black hole (IMBH), a mass of about 14,000 M☉ follows from the velocities and positions of these three stars. However, our acceleration limits make such an IMBH nearly as unlikely as a chance occurrence of such a star association. Furthermore, there is no variable X-ray source in IRS13E despite the high density of dust and gas. Therefore, we conclude that is unlikely that IRS13E hosts a black hole massive enough to bind the three stars.

Globular clusters in the near–infrared

The study of Globular Cluster (GC) stellar populations (SPs) addresses fundamental astrophysical questions ranging from stellar structure, evolution and dynamics, to Galaxy formation. Indeed, they represent:i)fossilsfrom the remote and violent epoch of Galaxy formation,ii) test particles for studying Galaxy dynamics and stellar dynamical model, andiii) fiducial templates for studying integrated light from distant stellar systems. In particular,high resolution spectroscopyof GC SPs provides abundance patterns which are crucial for understanding the formation and chemical enrichment time–scale of the host galaxy. Here the major results on Galactic GCs based on high-resolution near-infrared (near–IR) spectroscopy are briefly reviewed. Optical and IR spectroscopy are complementary tools to investigate SPs in different environments, the latter being more suitable in the case of moderately–high extinction regions (AV≥2) and high metallicity.

Circumnuclear Gas in Seyfert 1 Galaxies: Morphology, Kinematics, and Direct Measurement of Black Hole Masses

(Abridged) The two-dimensional distribution and kinematics of the molecular, ionized, and highly ionized gas in the nuclear regions of Seyfert 1 galaxies have been measured using high spatial resolution (~0''.09) near-infrared spectroscopy from NIRSPEC with adaptive optics on the Keck telescope. Molecular hydrogen, H2, is detected in all nine Seyfert 1 galaxies and, in the majority of galaxies, has a spatially resolved flux distribution. In contrast, the narrow component of the BrG emission has a distribution consistent with that of the K-band continuum. In general, the kinematics of H2 are consistent with thin disk rotation, with a velocity gradient of over 100 km/s measured across the central 0''.5 in three galaxies, and across the central 1''.5 in two galaxies. The kinematics of BrG are in agreement with the H2 rotation, except in all four cases the central 0''.5 is either blue- or redshifted by more than 75 km/s. The highly ionized gas, measured with the [Ca VIII] and [Si VII] coronal lines, is spatially and kinematically consistent with BrG in the central 0''.5. Dynamical models have been fitted to the two-dimensional H2 kinematics, taking into account the stellar mass distribution, the emission line flux distribution, and the point spread function. For NGC 3227 the modeling indicates a black hole mass of Mbh = 2.0{+1.0/-0.4} x 10^7 Msun, and for NGC 4151 Mbh = 3.0{+0.75/-2.2} x 10^7 Msun. In NGC 7469 the best fit model gives Mbh < 5.0 x 10^7 Msun. In all three galaxies, modeling suggests a near face-on disk inclination angle, which is consistent with the unification theory of active galaxies. The direct black hole mass estimates verify that masses determined from the technique of reverberation mapping are accurate to within a factor of three with no additional systematic errors.

Super Star Cluster Velocity Dispersions and Virial Masses in the M82 Nuclear Starburst

We use high-resolution near-infrared spectroscopy from Keck Observatory to measure the stellar velocity dispersions of 19 super star clusters (SSCs) in the nuclear starburst of M82. The clusters have ages on the order of 10 Myr, which is many times longer than the crossing times implied by their velocity dispersions and radii. We therefore apply the Virial Theorem to derive the kinematic mass for 15 of the SSCs. The SSCs have masses of 2 x 10^5 to 4 x 10^6 solar masses, with a total population mass of 1.4 x 10^7 solar masses. Comparison of the loci of the young M82 SSCs and old Milky Way globular clusters in a plot of radius versus velocity dispersion suggests that the SSCs are a population of potential globular clusters. We present the mass function for the SSCs, and find a power law fit with an index of gamma = -1.91 +/- 0.06. This result is nearly identical to the mass function of young SSCs in the Antennae galaxies.

Evaluation of Nonstarch Polysaccharides and Oligosaccharide Content of Different Soybean Varieties (Glycine max) by Near-Infrared Spectroscopy and Proteomics

A total of 832 samples of soybeans were screened by near-infrared (NIR) reflectance spectroscopy, to identify soybean samples with a lower content of oligosaccharides and nonstarch polysaccharides (NSP). Of these, 38 samples were identified on the basis of variation in protein content and agronomic value and submitted to high-resolution NIR spectroscopy. On the basis of the NIR data, 12 samples were further selected for chromatographic characterization of carbohydrate composition (mono-, di-, and oligosaccharides and NSP). Their soluble proteins were separated by two-dimensional gel electrophoresis (2DE). Using partial least-squares regression (PLSR), it was possible to predict the content of total NSP from the high-resolution NIR spectra, suggesting that NIR is a suitable and rapid nondestructive method to determine carbohydrate composition in soybeans. The 2DE analyses showed varying intensities of several proteins, including the glycinin G1 precursor. PLSR analysis showed a negative correlation between this protein and insoluble NSP and total uronic acid (UA).

The Double-lined Spectrum of LBV 1806-20

Despite much theoretical and observational progress, there is no known firm upper limit to masses of stars. Our understanding of interplay between immense radiation pressure produced by massive stars in formation and opacity of infalling material is subject to theoretical uncertainties, and many observational claims of the most massive have failed singularity test. LBV 1806-20 is a particularly luminous object, L ~ 106 L⊙, for which some have claimed very high mass estimates (Minitial > 200 M⊙), based in part on its similarity to Pistol star. We present high-resolution near-infrared spectroscopy of LBV 1806-20, showing that it is possibly a binary system with components separated in velocity by ~70 km s-1. If correct, then this system is not most massive star known, yet it is a massive binary system. We argue that a binary, or merged, system is more consistent with ages of nearby stars in LBV 1806-20 cluster. In addition, we find that velocity of VLSR = 36 km s-1 is consistent with a distance of 11.8 kpc, a luminosity of 106.3 L⊙, and a system mass of ~130 M⊙.

Carbon Isotope Ratio in12CO/13CO toward Local Molecular Clouds with Near‐Infrared High‐Resolution Spectroscopy of Vibrational Transition Bands

We report the carbon monoxide isotope ratio in local molecular clouds toward LkHα 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of 12CO ν = 2 ← 0 and 13CO ν = 1 ← 0 were observed with high-resolution near-infrared spectroscopy (R = 23,000) to measure the 12CO/13CO ratio. The isotopic ratios are 12CO/13CO = 137 ± 9 (LkHα 101), 86 ± 49 (AFGL 490), and 158 (Mon R2 IRS 3), which are 1.5-2.8 times higher than the local interstellar medium value of 12CO/13CO = 57 ± 5 from millimeter C18O emission observations. This is not easily explained by saturation of the 13CO absorption. It is also questionable whether the selective photodestruction of 13CO can account for the difference between the Galactic trend and the present observation, because the molecular clouds are with high visible extinction (AV = 10-70 mag), well shielded from destructive FUV radiation. The molecular gas associated with AFGL 490 and Mon R2 IRS 3 consists of multiple temperature components lying in the lines of sight. In the cool component (Tex < 100 K), the excitation temperature of 12CO is twice that of 13CO. We attribute the temperature discrepancy to the photon-trapping effect, which makes the radiative cooling of the main isotopomer less effective.

The Smallest Mass Ratio Young Star Spectroscopic Binaries

Using high-resolution near-infrared spectroscopy with the Keck Telescope, we have detected the radial velocity signatures of the cool secondary components in four optically identified pre-main-sequence, single-lined spectroscopic binaries. All are weak-lined T Tauri stars with well-defined center-of-mass velocities. The mass ratio for one young binary, NTTS 160905-1859, is M2/M1 = 0.18 ± 0.01, the smallest yet measured dynamically for a pre-main-sequence spectroscopic binary. These new results demonstrate the power of infrared spectroscopy for the dynamical identification of cool secondaries. Visible-light spectroscopy, to date, has not revealed any pre-main-sequence secondary stars with masses <0.5 M☉, while two of the young systems reported here are in that range. We compare our targets with a compilation of the published young, double-lined spectroscopic binaries and discuss our unique contribution to this sample.

IRAS F10214+4724: the inner 100 pc

We use new high-resolution near-infrared spectroscopy and our previously published optical spectroscopy of the gravitationally lensed Seyfert 2 galaxy F10214+4724 to study both the links between the starburst and AGN in this object and the properties of the line-emitting clouds in the inner narrow-line region. Close inspection of the rest frame UV spectrum reveals interstellar or stellar absorption features consistent with a compact, moderately reddened starburst providing about half the UV light, and explaining the dilution of the UV continuum polarization relative to the broad emission lines. Spectroscopy of the Hα/[N ii] line blend has enabled us to assess the relative contributions of the emission from the narrow-line region of the Seyfert 2, and a moderately reddened emission-line region which we argue is associated with the starburst activity. Estimates of the star formation rate from the unpolarized UV continuum flux and the Hα flux are consistent to within their associated uncertainties. We find we can plausibly explain the unusual emission-line properties of F10214+4724 in terms of conventional models for nearby Seyfert 2 galaxies if lensing is preferentially magnifying the side of the inner narrow-line region between the AGN and the observer, and the other side is both less magnified and partially obscured by the torus. The hydrogen densities of clouds in this region are high enough to make the Balmer lines optically thick and to suppress forbidden emission lines with low critical densities. From the emission-line spectrum we have deduced the column density of both ionized and neutral gas in the narrow-line clouds, and the density of the ionized gas. Using these we have been able to estimate the mass of the inner narrow-line clouds to be ∼ 1 M, and show that the gas:dust ratio NH/E(B−V) in these clouds must be ∼ 1.3 × 1027 m−2 mag−1, significantly higher than the average value in the Milky Way, ∼ 4.5 × 1025 m−2 mag−1. The column density and low dust content of a typical cloud are consistent with the properties of the warm absorbers seen in the X-ray spectra of Seyfert 1 galaxies. Our results thus favour models in which the narrow-line clouds start life close to the nucleus and flow out. An emission line from the lensing system has allowed us to confirm its redshift as z ≈ 0.9.

Molecular Gas and Star Formation in the Host Galaxy of the QSO I Zw 1

We have investigated the ISM of the I Zw 1 QSO host galaxy with Plateau de Bure mm-interferometry and high angular resolution near-infrared imaging spectroscopy. We have detected a circumnuclear gas ring of diameter ~ 1.5'' (1.8 kpc) in its millimetric CO line emission and have mapped the disk and the spiral arms of the host galaxy in the ^{12}CO(1-0) line at 115 GHz as well as in the H (1.65 um) and K (2.2 um) band . Combining our new mm- and NIR-data with available estimates of the radio- and far-infrared contributions to the nuclear emission, we find strong evidence for a nuclear starburst ring. A comparison to other sources with nuclear activity indicates that these rings may be a common phenomenon and contribute a large fraction of the central luminosity.