near-IR Spectroscopic Study Research Articles

Near-IR spectroscopic studies of galaxies at z ∼ 1–3

AbstractISM comprises multiple components, including molecular, neutral, and ionized gas, and dust, which are related to each other mainly through star formation – some are fuel for star formation (molecular gas) while some are the products of it (ionized gas, dust). To fully understand the physics of star formation and its evolution throughout cosmic time, it is crucial to measure and observe different ISM components of galaxies out to high redshifts. I will review the current status of near-IR studies of galaxies during the peak of star formation activity (z ∼ 1 – 3). Using rest-frame optical emission lines, we measure dust, star formation, and gaseous properties of galaxies. JWST will advance such studies by probing lower luminosities and higher redshifts, owing to its significantly higher sensitivity. Incorporating ALMA observations of cold dust and molecular gas at z > 1 will give us a nearly complete picture of the ISM in high-redshift galaxies over a large dynamic range in mass.

High-resolution Near-IR Spectral Mapping with H2 and [Fe ii] Lines of Multiple Outflows around LkHα 234

Abstract We present a high-resolution, near-IR spectroscopic study of multiple outflows in the LkHα 234 star formation region using the Immersion GRating INfrared Spectrometer (IGRINS). Spectral mapping over the blueshifted emission of HH 167 allowed us to distinguish at least three separate, spatially overlapped outflows in H2 and [Fe ii] emission. We show that the H2 emission represents not a single jet but rather complex multiple outflows driven by three known embedded sources: MM1, VLA 2, and VLA 3. There is a redshifted H2 outflow at a low velocity, V LSR <+50 km s−1, with respect to the systemic velocity of V LSR = −11.5 km s−1, that coincides with the H2O masers seen in earlier radio observations 2″ southwest of VLA 2. We found that the previously detected [Fe ii] jet with 100 km s−1 driven by VLA 3B is also detected in H2 emission and confirm that this jet has a position angle of about 240°. Spectra of the redshifted knots at 14″–65″ northeast of LkHα 234 are presented for the first time. These spectra also provide clues to the existence of multiple outflows. We detected high-velocity (50–120 km s−1) H2 gas in the multiple outflows around LkHα 234. Since these gases move at speeds well over the dissociation velocity (>40 km s−1), the emission must originate from the jet itself rather than H2 gas in the ambient medium. Also, position–velocity and excitation diagrams indicate that emission from knot C in HH 167 comes from two different phenomena, shocks and photodissociation.

Hybrid Organo–Inorganic Clay with Nonionic Interlayers. Mid- and Near-IR Spectroscopic Studies

The intercalation of organic polymers molecules (i.e., PEGs and BRIJ) into a standard Ca-montmorillonite has been studied by XRD, TG, and IR spectroscopy. The polymer intercalation is confirmed by the increasing of the d(001) in XRD spectra as well as by the complex multisteps thermal decomposition behavior of the organo-clay materials. Mid-IR and diffuse reflectance near-IR spectra of the intercalated materials show the polymer diagnostic bands (CH stretching and deformation mode), shifted or changed in shape by the interaction with the clay matrix. Both PEG 1500 and PEG 4000 based materials are likely intercalated in an extended configuration, similar to the amorphous polymer form. BRIJ intercalated polymer spectra suggest the disordered conformation of the alkilic chain in a prevailing "gauche", poorly packed, conformation. Host montmorillonite IR bands, mainly OH and water stretching and deformation fundamentals, combination, and overtone bands, are reduced in intensity by polymer intercalation, pointing out an interaction, likely through H-bonding and/or a possible substitution of cations hydration water molecules.

HIGH-VELOCITY NEON LINE EMISSION FROM THE ULIRG IRAS F00183-7111: REVEALING THE OPTICALLY OBSCURED BASE OF A NUCLEAR OUTFLOW

We report the first mid-IR detection of highly disturbed ionized gas in the ultraluminous infrared galaxy IRAS F00183-7111. The gas, traced by the 12.81um [NeII] and 15.56um [NeIII] lines, spans a velocity range of-3500 to 3000 km/s with respect to systemic velocity. Optical and near-IR spectroscopic studies show no evidence for similarly high velocity gas components in forbidden lines at shorter wavelengths. We interpret this as the result of strong extinction (Av=10-50) on the high-velocity gas, which identifies the base of the outflow traced in 5007A [OIII] as a plausible origin. Unusual excitation conditions are implied by a comparison of the mid-infrared low-excitation neon line emission and the PAH emission for a sample of 56 ULIRGs. For IRAS F00183, the neon/PAH ratio is 8 times higher than the average ratio. Similar mid-infrared kinematic and excitation characteristics are found for only 2 other ULIRGs in our sample: IRAS 12127-1412NE and IRAS 13451+1232. Both sources have an elevated neon/PAH ratio and exhibit pronounced blue wings in their 15.56um [NeIII] line profiles. IRAS 13451 even shows a strongly blue shifted and broad 14.32um [NeV] line. While for IRAS 13451 the observed [NeIII]/[NeII] and [NeV]/[NeII] line ratios indicate exposure of the blue shifted gas to direct radiation from the AGN, for IRAS F00183 and 12127 the neon line ratios are consistent with an origin in fast shocks in a high-density environment, and with an evolutionary scenario in which strongly blue shifted [Ne II] and [Ne III] emission trace the (partial) disruption of the obscuring medium around a buried AGN. The detection of strongly blue shifted [Ne V] emission in IRAS 13451 would then indicate this process to be much further advanced in this ULIRG than in IRAS F00183 and 12127, where this line is undetected.

Metal-Enriched Gaseous Halos around Distant Radio Galaxies: Clues to Feedback in Galaxy Formation

We present the results of an optical and near-IR spectroscopic study of giant nebular emission-line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07, and B2 0902+34. Previous deep narrowband Lyα imaging revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s^(-1) and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions >1000 km s^(-1). The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of ≈60 kpc along the radio axis. The dynamical structures traced in the Lyα line are, in most cases, closely echoed in the carbon and oxygen lines. This shows that the Lyα line is produced in a highly clumped medium of small filling factor and can therefore be used as a tracer of the dynamics of high-redshift radio galaxies (HzRGs). We conclude that these HzRGs are undergoing a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming red and dead elliptical galaxies.

Synthesis and Characterization of Water Soluble Single-Walled Carbon Nanotube Graft Copolymers

Poly(aminobenzene sulfonic acid) (PABS) and polyethylene glycol (PEG) were covalently attached to single-walled carbon nanotubes (SWNTs) to form water-soluble graft copolymers. Quantitative near-IR (NIR) spectroscopic studies of these SWNT graft copolymers indicate a water solubility of about 5 mg/mL, and atomic force microscopy studies show a fairly uniform length and diameter. On the basis of thermogravimetric analysis, the loading of SWNTs in the graft copolymers is estimated to be 30% for SWNT-PABS and 71% for SWNT-PEG. NIR spectroscopic studies of SWNT-PABS show that this graft copolymer has a ground state that is a hybrid of the electronic structures of the isolated PABS and SWNT macromolecules.

Modification of kaolinite surfaces through mechanochemical treatment—a mid-IR and near-IR spectroscopic study

The modification of kaolinite surfaces through mechanochemical treatment has been studied using a combination of mid-IR and near-IR spectroscopy. Kaolinite hydroxyls were lost after 10 h of grinding as evidenced by the decrease in intensity of the OH stretching vibrations at 3695 and 3619 cm −1 and the deformation modes at 937 and 915 cm −1. Concomitantly an increase in the hydroxyl-stretching vibrations of water is observed. The mechanochemical activation (dry grinding) causes destruction in the crystal structure of kaolinite by the rupture of the OH, AlOH, AlOSi and SiO bonds. Evidence of this destruction may be followed using near-IR spectroscopy. Two intense bands are observed in the spectral region of the first overtone of the hydroxyl-stretching vibration at 7065 and 7163 cm −1. These two bands decrease in intensity with mechanochemical treatment and two new bands are observed at 6842 and 6978 cm −1 assigned to the first overtone of the hydroxyl-stretching band of water. Concomitantly the water combination bands observed at 5238 and 5161 cm −1 increase in intensity with mechanochemical treatment. The destruction of the kaolinite surface may be also followed by the loss of intensity of the two hydroxyl combination bands at 4526 and 4623 cm −1. Infrared spectroscopy shows that the kaolinite surface has been modified by the removal of the kaolinite hydroxyls and their replacement with water adsorbed on the kaolinite surface. NIR spectroscopy enables the determination of the optimum time for grinding of the kaolinite. Further NIR allows the possibility of continual on-line analysis of the mechanochemical treatment of kaolinite.

Compositional Variability of the Serenitatis/Tranquillitatis Region of the Moon from Telescopic Multispectral Imaging and Spectroscopy

We present results from a combined CCD multispectral imaging and near-IR spectroscopic study of a region near the border between the Mare Serenitatis and Mare Tranquillitatis lunar impact basins. We have detected and spatially mapped variations in mare TiO2 abundance, in the degree of spectral maturity of impact craters and their ejecta blankets, and in the level of fresh highlands contamination within mare units. Techniques employed include color ratio images, image-oriented linear mixing models, and spectral band analyses. Specific findings include the detection of relatively fresh highlands materials in the craters Tacquet and Sulpicius Gallus and in the central peak and floor of the crater Plinius, the detection of low-TiO2 Serenitatis-like mare materials in a confined region of the ejecta from the crater Dawes, and the determination of immaturity rather than composition as the origin of the high albedo in the rectangular deposit surrounding Dawes. The combination of high spatial resolution imaging and high spectral resolution spectroscopy and the use of synthesizing techniques such as mixture modeling will provide valuable tools to optimize the scientific return from telescopic, Galileo, Clementine, and other future lunar data sets.

Visible and Near-IR Spectroscopic Studies of UCl4 in a Basic Ambient Temperature Melt: The Observation of a Possible Geometric Distorted UCl6 2− Species and the Evidence for the Hydrogen-Bond in the Melt

Visible and Near-IR Spectroscopic Studies of UCl4 in a Basic Ambient Temperature Melt: The Observation of a Possible Geometric Distorted UCl6 2− Species and the Evidence for the Hydrogen-Bond in the Melt

Luminescence from optical elements commonly used in near-IR spectroscopic studies: the photosensitized formation of singlet molecular oxygen ( 1Δ g) in solution

Upon excitation with visible light, optical elements made from silicon luminesce in the near-IR portion of the spectrum (1000 – 1300 nm). Excitation and emission spectra of optical grade silicon, recorded at 295 K, are presented in this report. The luminescence decay times depend both on the sample and on the experimental conditions. An emission spectrum of a Schott RG-850 filter is also reported. In most cases, interfering luminescence observed in time-resolved phosphorescence studies of singlet molecular oxygen (O 2( 1Δ g)), created by pulsed excitation of a sensitizer, can be attributed to the presence of optical elements which absorb visible radiation and subsequently emit in the near IR: either a silicon window, an interference filter containing a silicon blocking filter, or a standard colored glass filter.