In this paper, we study the characteristics of the member firms on the Korea Exchange. The member firms intermediate between the market participants and the exchange, and all the participants should trade stocks through members. To identify the chara
cteristics of member firms, all member firms are categorized into three groups, such as the domestic members similar to individuals (DIMs), the domestic members similar to institutions (DSMs), and the foreign members (FRMs), in terms of the type of investor. We examine the dynamics of the member firms. The trading characteristics of members are revealed through the directionality and trend. While FRMs tend to trade one-way and move with the price change, DIMs are the opposite. In the market, DIMs and DSMs do herd and the herding moves in the opposite direction of the price change. One the other hand, FRMs do herd in the direction of the price change. The network analysis supports that the members are clustered into three groups similar to DIMs, DSMs, and FRMs. Finally, random matrix theory and a cross-sectional regression show that the inventory variation of members possesses significant information about stock prices and that member herding helps to price the stocks.
We report Arecibo 21 cm absorption-emission observations to characterise the physical properties of neutral hydrogen (HI) in the proximity of five giant molecular clouds (GMCs): Taurus, California, Rosette, Mon OB1, and NGC 2264. Strong HI absorption
was detected toward all 79 background continuum sources in the ~60x20 square degree region. Gaussian decompositions were performed to estimate temperatures, optical depths and column densities of the cold and warm neutral medium (CNM, WNM). The properties of individual CNM components are similar to those previously observed along random Galactic sightlines and in the vicinity of GMCs, suggesting a universality of cold HI properties. The CNM spin temperature (Ts) histogram peaks at ~50K. The turbulent Mach numbers of CNM vary widely, with a typical value of ~4, indicating that their motions are supersonic. About 60% of the total HI gas is WNM, and nearly 40% of the WNM lies in thermally unstable regime 500-5000K. The observed CNM fraction is higher around GMCs than in diffuse regions, and increases with increasing column density (NHI) to a maximum of ~75%. On average, the optically thin approximation (N*(HI)) underestimates the total N(HI) by ~21%, but we find large regional differences in the relationship between N(HI) and the required correction factor, f=N(HI)/N*(HI). We examine two different methods (linear fit of f vs log10(N*(HI)) and uniform Ts) to correct for opacity effects using emission data from the GALFA-HI survey. We prefer the uniform Ts method, since the linear relationship does not produce convincing fits for all subregions.
With an aim of probing the physical conditions and excitation mechanisms of warm molecular gas in individual star-forming regions, we performed Herschel SPIRE FTS observations of 30 Doradus in the LMC. In our FTS observations, important FIR cooling l
ines in the ISM, including CO J=4-3 to 13-12, [CI] 370 micron, and [NII] 205 micron, were clearly detected. In combination with ground-based CO data, we then constructed CO spectral line energy distributions (SLEDs) on 10 pc scales over a 60 pc x 60 pc area and found that the shape of the observed CO SLEDs considerably changes across 30 Doradus, e.g., the peak transition varies from J=6-5 to 10-9, while the slope characterized by the high-to-intermediate J ratio ranges from 0.4 to 1.8. To examine the source(s) of these variations in CO transitions, we analyzed the CO observations, along with [CII] 158 micron, [CI] 370 micron, [OI] 145 micron, H2 0-0 S(3), and FIR luminosity data, using state-of-the-art models of PDRs and shocks. Our detailed modeling showed that the observed CO emission likely originates from highly-compressed (thermal pressure ~ 1e7-1e9 K cm-3) clumps on 0.7-2 pc scales, which could be produced by either UV photons (UV radiation field ~ 1e3-1e5 Mathis fields) or low-velocity C-type shocks (pre-shock medium density ~ 1e4-1e6 cm-3 and shock velocity ~ 5-10 km s-1). Considering the stellar content in 30 Doradus, however, we tentatively excluded the stellar origin of CO excitation and concluded that low-velocity shocks driven by kpc scale processes (e.g., interaction between the Milky Way and the Magellanic Clouds) are likely the dominant source of heating for CO. The shocked CO-bright medium was then found to be warm (temperature ~ 100-500 K) and surrounded by a UV-regulated low pressure component (a few (1e4-1e5) K cm-3) that is bright in [CII] 158 micron, [CI] 370 micron, [OI] 145 micron, and FIR dust continuum emission.
The local interstellar medium (ISM) is suffused with dark gas, identified by excess infrared and gamma ray emission, yet undetected by standard ISM tracers such as neutral hydrogen (HI) or carbon monoxide emission. Based on observed dust properties f
rom Planck, recent studies have argued that HI mixed with dust is strongly saturated and that dark gas is dominated by optically-thick HI. We test this hypothesis by reproducing this model using data from Planck and new 21 cm emission maps from GALFA-HI -- the first large-area 21cm emission survey with comparable angular resolution to Planck. We compare the results with those from a large sample of HI column densities based on direct observations of HI optical depth, and find that the inferred column density corrections are significantly lower than those inferred by the Planck-based model. Further, we rule out the hypothesis that the pencil-beam HI absorption sight lines preferentially miss opaque blobs with small covering fraction, as these structures require densities and pressures which are incompatible with ISM conditions. Our results support the picture that excess dust emission in the local ISM is not dominated by optically-thick HI, but is rather a combination of intrinsic changes in dust grain emissivities and H2 missed by CO observations.
We present Herschel SPIRE Fourier Transform Spectrometer (FTS) observations of N159W, an active star-forming region in the Large Magellanic Cloud (LMC). In our observations, a number of far-infrared cooling lines including CO(4-3) to CO(12-11), [CI]
609 and 370 micron, and [NII] 205 micron are clearly detected. With an aim of investigating the physical conditions and excitation processes of molecular gas, we first construct CO spectral line energy distributions (SLEDs) on 10 pc scales by combining the FTS CO transitions with ground-based low-J CO data and analyze the observed CO SLEDs using non-LTE radiative transfer models. We find that the CO-traced molecular gas in N159W is warm (kinetic temperature of 153-754 K) and moderately dense (H2 number density of (1.1-4.5)e3 cm-3). To assess the impact of the energetic processes in the interstellar medium on the physical conditions of the CO-emitting gas, we then compare the observed CO line intensities with the models of photodissociation regions (PDRs) and shocks. We first constrain the properties of PDRs by modelling Herschel observations of [OI] 145, [CII] 158, and [CI] 370 micron fine-structure lines and find that the constrained PDR components emit very weak CO emission. X-rays and cosmic-rays are also found to provide a negligible contribution to the CO emission, essentially ruling out ionizing sources (ultraviolet photons, X-rays, and cosmic-rays) as the dominant heating source for CO in N159W. On the other hand, mechanical heating by low-velocity C-type shocks with ~10 km/s appears sufficient enough to reproduce the observed warm CO.
We apply the Sternberg et al. (2014) theoretical model to analyze HI and H2 observations in the Perseus molecular cloud. We constrain the physical properties of the HI shielding envelopes and the nature of the HI-to-H2 transitions. Our analysis (Bial
y et al. 2015) implies that in addition to cold neutral gas (CNM), less dense thermally-unstable gas (UNM) significantly contributes to the shielding of the H2 cores in Perseus.
(Abridged) Using the Arecibo Observatory we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines w
ere detected in all cases allowing us to estimate spin temperature (T_s) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual HI clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium, CNM and WNM) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium HI survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have on average a higher total HI column density and the CNM fraction, suggesting an enhanced amount of cold HI relative to an average interstellar field. Our estimated optical depth and spin temperature are in stark contrast with the recent attempt at using Planck data to estimate properties of the optically thick HI. Only ~15% of lines of sight in our study have a column density weighted average spin temperature lower than 50 K, in comparison with >85% of Plancks sky coverage. The observed CNM fraction is inversely proportional to the optical-depth weighted average spin temperature, in excellent agreement with the recent numerical simulations by Kim et al. While the CNM fraction is on average higher around Perseus relative to a random interstellar field, it is generally low, 10-50%. This suggests that extended WNM envelopes around molecular clouds, and/or significant mixing of CNM and WNM throughout molecular clouds, are present and should be considered in the models of molecule and star formation.
We derive the CO-to-H2 conversion factor, X_CO = N(H2)/I_CO, across the Perseus molecular cloud on sub-parsec scales by combining the dust-based N(H2) data with the I_CO data from the COMPLETE Survey. We estimate an average X_CO ~ 3 x 10^19 cm^-2 K^-
1 km^-1 s and find a factor of ~3 variations in X_CO between the five sub-regions in Perseus. Within the individual regions, X_CO varies by a factor of ~100, suggesting that X_CO strongly depends on local conditions in the interstellar medium. We find that X_CO sharply decreases at Av < 3 mag but gradually increases at Av > 3 mag, with the transition occurring at Av where I_CO becomes optically thick. We compare the N(HI), N(H2), I_CO, and X_CO distributions with two models of the formation of molecular gas, a one-dimensional photodissociation region (PDR) model and a three-dimensional magnetohydrodynamic (MHD) model tracking both the dynamical and chemical evolution of gas. The PDR model based on the steady state and equilibrium chemistry reproduces our data very well but requires a diffuse halo to match the observed N(HI) and I_CO distributions. The MHD model generally matches our data well, suggesting that time-dependent effects on H2 and CO formation are insignificant for an evolved molecular cloud like Perseus. However, we find interesting discrepancies, including a broader range of N(HI), likely underestimated I_CO, and a large scatter of I_CO at small Av. These discrepancies likely result from strong compressions/rarefactions and density fluctuations in the MHD model.
