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Kaplan, Kyle F.,Dinerstein, Harriet L.,Oh, Heeyoung,Mace, Gregory N.,Kim, Hwihyun,Sokal, Kimberly R.,Pavel, Michael D.,Lee, Sungho,Pak, Soojong,Park, Chan,Oh, Jae Sok,Jaffe, Daniel T. American Astronomical Society 2017 The Astrophysical journal Vol.838 No.2
<P>We present a deep near-infrared spectrum of the Orion Bar Photodissociation Region (PDR) taken with the Immersion Grating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at the McDonald Observatory. IGRINS has high spectral resolution (R similar to 45,000) and instantaneous broad wavelength coverage (1.45-2.45 mu m), enabling us to detect 87 emission lines from rovibrationally excited molecular hydrogen (H-2) that arise from transitions out of 69 upper rovibration levels of the electronic ground state. These levels cover a large range of rotational and vibrational quantum numbers and excitation energies, making them excellent probes of the excitation mechanisms of H2 and physical conditions within the PDR. The Orion Bar PDR is thought to consist of cooler high density clumps or filaments (T = 50-250 K, n(H) = 10(5)-10(7) cm(-3)) embedded in a warmer lower density medium (T = 250-1000 K, n(H) = 10(4)-10(5) cm(-3)). We fit a grid of constant temperature and density Cloudy models, which recreate the observed H2 level populations well, to constrain the temperature to a range of 600-650. K and the density to n(H) = 2.5 x 10(3) -10(4) cm(-3). The best-fit model gives T = 625 K and n(H) = 5 x 10(3) cm(-3). This well-constrained warm temperature is consistent with kinetic temperatures found by other studies for the Orion Bar's lower density medium. However, the range of densities well fit by the model grid is marginally lower than those reported by other studies. We could be observing lower density gas than the surrounding medium, or perhaps a density-sensitive parameter in our models is not properly estimated.</P>
THREE-DIMENSIONAL SHOCK STRUCTURE OF THE ORION KL OUTFLOW WITH IGRINS
Oh, Heeyoung,Pyo, Tae-Soo,Kaplan, Kyle,Yuk, In-Soo,Park, Byeong-Gon,Mace, Gregory,Park, Chan,Chun, Moo-Young,Pak, Soojong,Kim, Kang-Min,Oh, Jae Sok,Jeong, Ueejeong,Yu, Young Sam,Lee, Jae-Joon,Kim, Hwi American Astronomical Society 2016 The Astrophysical journal Vol.833 No.2
<P>We report a study of the three-dimensional (3D) outflow structure of a 15 '' x 13 '' area around the H-2 peak 1 in Orion KL with slit-scan observations (13 slits) using the Immersion Grating Infrared Spectrograph. The datacubes have a high-velocity resolution (similar to 7.5 km s(-1)), provide high-contrast imaging within ultra-narrow bands, and enable the detection of the main stream of the previously reported H2 outflow fingers. We identified 31 distinct fingers in the H-2 1-0 S(1) lambda 2.122 mu m 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 similar to 4 km s(-1) arcsec(-1) agree well with the velocities inferred from large-scale proper motions, where the projected motion is proportional to the distance from a common origin. We construct a conceptual 3D map of the fingers with estimated inclination angles of 57 degrees-74 degrees. The extinction difference (Delta A(v) > 10 mag) between blueshifted and redshifted fingers indicates high internal extinction. The extinction, the overall angular spread, and the scale of the flow argue for an ambient medium with a very high density (10(5)-10(6) cm(-3)), consistent with molecular line observations of the Orion Molecular Cloud core. The radial velocity gradients and the 3D distributions of the fingers together support the hypothesis of a simultaneous radial explosion of the Orion KL outflow.</P>
Fluorescent H<sub>2</sub>Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS
Le, Huynh Anh N.,Pak, Soojong,Kaplan, Kyle,Mace, Gregory,Lee, Sungho,Pavel, Michael,Jeong, Ueejeong,Oh, Heeyoung,Lee, Hye-In,Chun, Moo-Young,Yuk, In-Soo,Pyo, Tae-Soo,Hwang, Narae,Kim, Kang-Min,Park, C American Astronomical Society 2017 The Astrophysical journal Vol.841 No.1
<P>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 similar or equal to 45,000 with the Immersion GRating INfrared Spectrograph, we detected 68 H-2 emission lines within the 1 '' x 15 '' slit. The diagnostic ratio of 2-1 S(1)/1-0 S(1) is 0.41-0.56. In addition, the estimated ortho-to-para ratio (OPR) is 1.63-1.82, indicating that the H-2 emission transitions in the observed region arise 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 v = 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 '' x 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 similar to 10(5) cm(-3) with a size smaller than similar to 5 x 10(- 3) pc embedded in lower-density regions of 10(3)-10(4) cm(-3).</P>
The Spectrum of SS 433 in the<i>H</i>and<i>K</i>Bands
Robinson, Edward L.,Froning, Cynthia S.,Jaffe, Daniel T.,Kaplan, Kyle F.,Kim, Hwihyun,Mace, Gregory N.,Sokal, Kimberly R.,Lee, Jae-Joon American Astronomical Society 2017 The Astrophysical journal Vol.841 No.2
<P>SS 433 is an X-ray binary and the source of sub-relativistic, precessing, baryonic jets. We present high-resolution spectrograms of SS. 433 in the infrared H and K bands. The spectrum is dominated by hydrogen and helium emission lines. The precession phase of the emission lines from the jet continues to be described by a constant period, P-jet = 162.375 days. The limit on any secularly changing period is |P| less than or similar to 10(-5). The He I lambda 2.0587 mu m line has complex and variable P-Cygni absorption features produced by an inhomogeneous wind with a maximum outflow velocity near 900 km s(-1). The He II emission lines in the spectrum also arise in this wind. The higher members of the hydrogen Brackett lines show a double-peaked profile with symmetric wings extending more than +/- 1500 km s(-1) from the line center. The lines display radial velocity variations in phase with the radial velocity variation expected of the compact star, and they show a distortion during disk eclipse that we interpret as a rotational distortion. We fit the line profiles with a model in which the emission comes from the surface of a symmetric, Keplerian accretion disk around the compact object. The outer edge of the disk has velocities that vary from 110 to 190 km s(-1). These comparatively low velocities place an important constraint on the mass of the compact star: its mass must be less than 2.2 M-circle dot and is probably less than 1.6 M-circle dot</P>
THE CHEMICAL COMPOSITIONS OF VERY METAL-POOR STARS HD 122563 AND HD 140283: A VIEW FROM THE INFRARED
Afş,ar, Melike,Sneden, Christopher,Frebel, Anna,Kim, Hwihyun,Mace, Gregory N.,Kaplan, Kyle F.,Lee, Hye-In,Oh, Heeyoung,Oh, Jae Sok,Pak, Soojong,Park, Chan,Pavel, Michael D.,Yuk, In-Soo,Jaffe, Dan American Astronomical Society 2016 The Astrophysical journal Vol.819 No.2
<P>From high resolution (R similar or equal to 45,000), high signal-to-noise ratio (S/N > 400) spectra gathered with the Immersion Grating Infrared Spectrograph (IGRINS) in the H and K photometric bands, we have derived elemental abundances of two bright, well-known metal-poor halo stars: the red giant HD 122563 and the subgiant HD 140283. Since these stars have metallicities approaching [Fe/H] = -3, their absorption features are generally very weak. Neutral-species lines of Mg, Si, S and Ca are detectable, as well as those of the light odd-Z elements Na and Al. The derived IR-based abundances agree with those obtained from optical-wavelength spectra. For Mg and Si the abundances from the infrared transitions are improvements to those derived from shorter wavelength data. Many useful OH and CO lines can be detected in the IGRINS HD 122563 spectrum, from which derived O and C abundances are consistent to those obtained from the traditional [O I] and CH features. IGRINS high resolutions Hand K-band spectroscopy offers promising ways to determine more reliable abundances for additional metal-poor stars whose optical features are either not detectable, or too weak, or are based on lines with analytical difficulties.</P>