The Immersion Grating Infrared Spectrometer (IGRINS) is a compact high-resolution near-infrared cross-dispersed spectrograph whose primary disperser is a silicon immersion grating. IGRINS covers the entire portion of the wavelength range between 1.45 and 2.45μm that is accessible from the ground and does so in a single exposure with a resolving power of 40,000. Individual volume phase holographic (VPH) gratings serve as cross-dispersing elements for separate spectrograph arms covering the H and K bands. On the 2.7m Harlan J. Smith telescope at the McDonald Observatory, the slit size is 1ʺ x 15ʺ and the plate scale is 0.27ʺ pixel -1 . The spectrograph employs two 2048 x 2048 pixel Teledyne Scientific & Imaging HAWAII-2RG detectors with SIDECAR ASIC cryogenic controllers. The instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows the spectrograph collimated beam size to be only 25mm, which permits a moderately sized (0.96m x 0.6m x 0.38m) rectangular cryostat to contain the entire spectrograph. The fabrication and assembly of the optical and mechanical components were completed in 2013. We describe the major design characteristics of the instrument including the system requirements and the technical strategy to meet them. We also present early performance test results obtained from the commissioning runs at the McDonald Observatory.
We have analyzed the temperature, velocity and density of H 2 gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By observing NGC 7023 in the H and K bands at R ≃ 45,000 with the Immersion GRating INfrared Spectrograph (IGRINS), we detected 68 H 2 emission lines within the 1 ′′ × 15 ′′ slit. The diagnostic ratios of 2-1 S(1)/1-0 S(1) is 0.41−0.56.In addition, the estimated ortho-to-para ratios (OPR) is 1.63−1.82, indicating that the H 2 emission transitions in the observed region arises mostly from gas excited by UV fluorescence. Gradients in the temperature, velocity, and OPR within the observed area imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H 2 from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rotational J levels of ν = 1, is that the predicted formation temperature for newly-formed H 2 should be lower than that of the model predictions. To investigate the density distribution, we combine pixels in 1 ′′ × 1 ′′ areas and derive the density distribution at the 0.002 pc scale. The derived gradient of density suggests that NGC 7023 has a clumpy structure, including a high clump density of ∼10 5 cm −3 with a size smaller than ∼5 × 10 −3 pc embedded in lower density regions of 10 3 −10 4 cm −3 .
We report a study of the three-dimensional (3D) outflow structure of a 15 ′′ × 13 ′′ area around H 2 peak 1 in Orion KL with slit-scan observations (13 slits) using the Immersion Grating Infrared Spectrograph. The datacubes, with high velocity-resolution (∼ 7.5 km s −1 ) provide high contrast imaging within ultranarrow bands, and enable the detection of the main stream of the previously reported H 2 outflow fingers. We identified 31 distinct fingers in H 2 1−0 S(1) λ2.122 µm emission. The line profile at each finger shows multiple-velocity peaks with a strong low-velocity component around the systemic velocity at V LSR = +8 km s −1 and high velocity emission (|V LSR | = 45−135 km s −1 ) indicating a typical bow-shock. The observed radial velocity gradients of ∼ 4 km s
We present the results of high-resolution near-IR spectroscopy toward the multiple outflows around the Herbig Be star LkHα 234 using the Immersion Grating Infrared Spectrograph (IGRINS). Previous studies indicate that the region around LkHα 234 is complex, with several embedded YSOs and the outflows associated with them. In simultaneous H− and K−band spectra from HH 167, we detected 5 [Fe II] and 14 H 2 emission lines. We revealed a new [Fe II] jet driven by radio continuum source VLA 3B. Position-velocity diagrams of H 2 1−0 S(1) λ2.122 µm line show multiple velocity peaks. The kinematics may be explained by a geometrical bow shock model. We detected a component of H 2 emission at the systemic velocity (V LSR = −10.2 km s −1 ) along the whole slit in all slit positions, which may arise from the ambient photodissociation region. Low-velocity gas dominates the molecular hydrogen emission from knots A and 2. We newly revealed an [Fe II] jet driven by radio source VLA 3B.3. The multiple velocity peaks we observe in H 2 emission lines are consistent with a generic bow shock model. Both knots A and B show this bow shock feature. Furthermore, the positional difference (∼ 1 ′′ ) between low-and high-velocity components may be caused by a difference between the wing and apex of the bow. 4. The molecular hydrogen emission is dominant at low-velocity with a radial velocity within 50 km s −1 of the systemic velocity, while [Fe II] emission is only presnet in the higher-
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