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Naomasa Nakai

Publications and source records attributed to Naomasa Nakai.

At least 37 records · Page 2Linked to original sources

ALMA [CI] observations toward the central region of a Seyfert galaxy NGC 613

We report ALMA observations of [CI]($^3P_1-^3P_0$), C$^{13}$O, and CO$^{18}$ ($J=1-0$) toward the central region of a nearby Seyfert galaxy NGC 613. The very high resolutions of $0.26"\times0.23"(=22\times20$ pc) for [CI] and $0.42"\times0.35"(=36\times30$ pc) for C$^{13}$O, and CO$^{18}$ resolve the circum-nuclear disk (CND) and star-forming ring. The distribution of [CI] in the ring resembles that of the CO emission, although [CI] is prominent in the CND. This can be caused by the low intensities of the CO isotopes due to the low optical depths under the high temperature in the CND. We found that the intensity ratios of [CI] to C$^{12}$O(3-2) ($R_{\rm CI/CO}$) and to C$^{13}$O(1-0) ($R_{\rm CI/C^{13}O}$) are high at several positions around the edge of the ring. The spectral profiles of CO lines mostly correspond each other in the spots of the ring and high $R_{\rm CI/CO}$, but those of [CI] at spots of high $R_{\rm CI/CO}$ are different from CO. These results indicate that [CI] at the high $R_{\rm CI/CO}$ traces different gas from that traced by the CO lines. The [CI] kinematics along the minor axis of NGC 613 could be interpreted as a bubbly molecular outflow. The outflow rate of molecular gas is higher than star formation rate in the CND. The flow could be mainly boosted by the AGN through its radio jets.

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Evolution of Molecular Clouds in the Superwind Galaxy NGC 1808 Probed by ALMA Observations

ALMA imaging of the cold molecular medium in the nearby starburst galaxy NGC 1808 is presented. The observations reveal the distribution of molecular gas, traced by $^{12}$CO (1-0) and $^{12}$CO (3-2), and continuum (93 and 350 GHz) across the central 1 kpc starburst region at high resolution of $\sim1$ arcsec. A molecular gas torus (radius $\sim30$ pc) is discovered in the circumnuclear disk (CND; central 100 pc), with a high CO (3-2)/CO (1-0) ratio of $\sim1$, surrounded by massive ($10^6$-$10^7$ $M_\odot$) clouds with high star formation efficiency (SFE$\sim10^{-8}$ yr$^{-1}$), molecular spiral arms, and a 500 pc pseudoring. The CND harbors a continuum core and molecular gas exhibiting peculiar motion. The new data confirm the line splitting along the minor galactic axis, interpreted as a nuclear gas outflow with average velocity $\sim180$ km s$^{-1}$, and show evidence of a velocity gradient of $\sim+0.4$ km s$^{-1}$ pc$^{-1}$ along the axis. In addition, supershells expanding from the 500 pc ring with maximum velocities of $\sim75$ km s$^{-1}$ are revealed. The distribution and CO luminosities of molecular clouds in the central 1 kpc starburst region indicate an evolutionary sequence, from gas accretion onto the 500 pc ring from the large-scale bar, to enhanced star formation in the ring, and outflow as feedback.

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Diverse nuclear star-forming activities in the heart of NGC 253 resolved with ten-pc scale ALMA images

We present an 8 pc x 5 pc resolution view of the central ~ 200 pc region of the nearby starburst galaxy NGC 253, based on ALMA Band 7 (λ ~ 0.85 mm or ν ~ 350 GHz) observations covering 11 GHz. We resolve the nuclear starburst of NGC 253 into eight dusty star-forming clumps, 10 pc in scale, for the first time. These clumps, each of which contains (4-10) x 10^4 M_sun of dust (assuming that the dust temperature is 25 K) and up to 6 x 10^2 massive (O5V) stars, appear to be aligned in two parallel ridges, while they have been blended in previous studies. Despite the similarities in sizes and dust masses of these clumps, their line spectra vary drastically from clump to clump although they are separated by only ~ 10 pc. Specifically, one of the clumps, Clump 1, exhibits line confusion-limited spectra with at least 36 emission lines from 19 molecules (including CH3OH, HNCO, H2CO, CH3CCH, H2CS, and H3O+) and a hydrogen recombination line (H26α), while much fewer kinds of molecular lines are detected in some other clumps where fragile species, such as complex organic molecules and HNCO, completely disappear from their spectra. We demonstrate the existence of hot molecular gas ($T_rot (SO2) = 90 {\pm} 11 K) in the former clump, which suggests that the hot and chemically rich environments are localized within a 10-pc scale star-forming clump.

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Discovery of H2O Megamasers in Obscured Active Galactic Nuclei

Recently a new method to discover obscured active galactic nuclei (AGNs) by utilizing X-ray and Infrared data has been developed. We carried out a survey of H2O maser emission toward ten obscured AGNs with the Nobeyama 45-m telescope. We newly detected the maser emission with the signal-noise-ratio (SNR) of above 4 from two AGNs, NGC 1402 and NGC 7738. We also found a tentative detection with its SNR > 3 in NGC 5037. The detection rate of 20% is higher than those of previous surveys (usually several percents).

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A Multi-Line Ammonia Survey of the Galactic Center Region with the Tsukuba 32-m Telescope - I. Observations and Data

We present survey data of the NH3 (J, K) = (1, 1)--(6, 6) lines, simultaneously observed with the Tsukuba 32-m telescope, in the main part of the central molecular zone of the Galaxy. The total number of on-source positions was 2655. The lowest three transitions were detected with S/N > 3 at 2323 positions (93% of all the on-source positions). Among 2323, the S/N of (J, K ) = (4, 4), (5, 5), and (6, 6) exceeded 3.0 at 1426 (54%), 1150 (43%), and 1359 (51%) positions, respectively. Simultaneous observations of the lines enabled us to accurately derive intensity ratios with less systematic errors. Boltzmann plots indicate there are two temperature components: cold ($\sim$ 20 K) and warm ($\sim$ 100 K). Typical intensity ratios of Tmb(2,2)/Tmb(1,1), Tmb(4,4)/Tmb(2,2), Tmb(5,5)/Tmb(4,4), and Tmb(6,6)/Tmb(3,3) were 0.71, 0.45, 0.65, and 0.17, respectively. These line ratios correspond to diversity of rotational temperature, which results from mixing of the two temperature components.

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CO Multi-line Imaging of Nearby Galaxies (COMING): I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903

We present simultaneous mappings of J=1-0 emission of 12CO, 13CO, and C18O molecules toward the whole disk (8' x 5' or 20.8 kpc x 13.0 kpc) of the nearby barred spiral galaxy NGC 2903 with the Nobeyama Radio Observatory 45-m telescope at an effective angular resolution of 20" (or 870 pc). We detected 12CO(J=1-0) emission over the disk of NGC 2903. In addition, significant 13CO(J=1-0) emission was found at the center and bar-ends, whereas we could not detect any significant C18O(J=1-0) emission. In order to improve the signal-to-noise ratio of CO emission and to obtain accurate line ratios of 12CO(J=2-1)/12CO(J=1-0) ($R_{2-1/1-0}$) and 13CO(J=1-0)/12CO(J=1-0) ($R_{13/12}$), we performed the stacking analysis for our 12CO(J=1-0), 13CO(J=1-0), and archival 12CO(J=2-1) spectra with velocity-axis alignment in nine representative regions of NGC 2903. We successfully obtained the stacked spectra of the three CO lines, and could measure averaged $R_{2-1/1-0}$ and $R_{13/12}$ with high significance for all the regions. We found that both $R_{2-1/1-0}$ and $R_{13/12}$ differ according to the regions, which reflects the difference in the physical properties of molecular gas; i.e., density ($n_{\rm H_2}$) and kinetic temperature ($T_K$). We determined $n_{\rm H_2}$ and $T_K$ using $R_{2-1/1-0}$ and $R_{13/12}$ based on the large velocity gradient approximation. The derived $n_{\rm H_2}$ ranges from ~ 1000 cm$^{-3}$ (in the bar, bar-ends, and spiral arms) to 3700 cm$^{-3}$ (at the center) and the derived $T_K$ ranges from 10 K (in the bar and spiral arms) to 30 K (at the center). We examined the dependence of star formation efficiencies (SFEs) on $n_{\rm H_2}$ and $T_K$, and found the positive correlation between SFE and $n_{\rm H_2}$ with the correlation coefficient for the least-square power-law fit $R^2$ of 0.50. This suggests that molecular gas density governs the spatial variations in SFEs.

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Gas Dynamics and Outflow in the Barred Starburst Galaxy NGC 1808 Revealed with ALMA

NGC 1808 is a nearby barred starburst galaxy with an outflow from the nuclear region. To study the inflow and outflow processes related to star formation and dynamical evolution of the galaxy, we have carried out \(^{12}\)CO (\(J=1-0\)) mapping observations of the central \(r\sim4\) kpc of NGC 1808 using the Atacama Large Millimeter/submillimeter Array (ALMA). Four distinct components of molecular gas are revealed at high spatial resolution of 2\arcsec (\(\sim100\) pc): (1) a compact (\(r<200\) pc) circumnuclear disk (CND), (2) \(r\sim500\) pc ring, (3) gas-rich galactic bar, and (4) spiral arms. Basic geometric and kinematic parameters are derived for the central 1-kpc region using tilted-ring modeling. The derived rotation curve reveals multiple mass components that include (1) a stellar bulge, (2) nuclear bar and molecular CND, and (3) unresolved massive (\(\sim10^7~M_\sun\)) core. Two systemic velocities, 998 km s\(^{-1}\) for the CND and 964 km s\(^{-1}\) for the 500-pc ring, are revealed, indicating a kinematic offset. The pattern speed of the primary bar, derived by using a cloud-orbit model, is \(56\pm11\) km s\(^{-1}\) kpc\(^{-1}\). Non-circular motions are detected associated with a nuclear spiral pattern and outflow in the central 1-kpc region. The ratio of the mass outflow rate to the star formation rate is \(\dot{M}_\mathrm{out}/SFR\sim0.2\) in the case of optically thin CO (1-0) emission in the outflow, suggesting low efficiency of star formation quenching.

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Submillimeter-HCN Diagram for an Energy Diagnostics in the Centers of Galaxies

Compiling data from literature and the ALMA archive, we show enhanced HCN(4-3)/HCO$^+$(4-3) and/or HCN(4-3)/CS(7-6) integrated intensity ratios in circumnuclear molecular gas around active galactic nuclei (AGNs) compared to those in starburst (SB) galaxies (submillimeter HCN-enhancement). The number of sample galaxies is significantly increased from our previous work. We expect this feature could potentially be an extinction-free energy diagnostic tool of nuclear regions of galaxies. Non-LTE radiative transfer modelings of the above molecular emission lines involving both collisional and radiative excitation, as well as a photon trapping effect were conducted to investigate the cause of the high line ratios in AGNs. As a result, we found that enhanced abundance ratios of HCN-to-HCO$^+$ and HCN-to-CS in AGNs as compared to SB galaxies by a factor of a few to even $>$ 10 is a plausible explanation for the submillimeter HCN-enhancement. However, a counter argument of a systematically higher gas density in AGNs than in SB galaxies can also be a plausible scenario. Although we could not fully discriminate these two scenarios at this moment due to insufficient amount of multi-transition, multi-species data, the former scenario equivalently claims for abnormal chemical composition in AGNs. Regarding the actual mechanism to realize the composition, we suggest it is difficult with conventional gas phase X-ray dominated region (XDR) ionization models to reproduce the observed high line ratios. We might have to take into account other mechanisms such as neutral-neutral reactions that are efficiently activated at high temperature environments and/or mechanically heated regions to further understand the high line ratios in AGNs.

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Large-scale CO (J=4-3) Mapping toward the Orion-A Giant Molecular Cloud

We have mapped the Orion-A Giant Molecular Cloud in the CO (J=4-3) line with the Tsukuba 30-cm submillimeter telescope.The map covered a 7.125 deg^2 area with a 9' resolution, including main components of the cloud such as Orion Nebula, OMC-2/3, and L1641-N. The most intense emission was detected toward the Orion KL region. The integrated intensity ratio between CO (J=4-3) and CO (J=1-0) was derived using data from the Columbia-Univ. de Chile CO survey, which was carried out with a comparable angular resolution. The ratio was r_{4-3/1-0} ~ 0.2 in the southern region of the cloud and 0.4-0.8 at star forming regions. We found a trend that the ratio shows higher value at edges of the cloud. In particular the ratio at the north-eastern edge of the cloud at (l, b) = (208.375 deg, -19.0 deg) shows the specific highest value of 1.1. The physical condition of the molecular gas in the cloud was estimated by non-LTE calculation. The result indicates that the kinetic temperature has a gradient from north (Tkin=80 K) to south (20 K). The estimation shows that the gas associated with the edge of the cloud is warm (Tkin~60 K), dense (n_{H_2}~10^4 cm^{-3}), and optically thin, which may be explained by heating and sweeping of interstellar materials from OB clusters.

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ALMA Observations of the Submillimeter Dense Molecular Gas Tracers in the Luminous Type-1 Active Nucleus of NGC 7469

We present ALMA Cycle 1 observations of the central kpc region of the luminous type-1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.5$"$ $\times$ 0.4$"$ = 165 pc $\times$ 132 pc) at submillimeter wavelengths. Utilizing the wide-bandwidth of ALMA, we simultaneously obtained HCN(4-3), HCO$^+$(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860 $μ$m continuum. The region consists of the central $\sim$ 1$"$ component and the surrounding starburst ring with a radius of $\sim$ 1.5$"$-2.5$"$. Several structures connect these components. Except for CO(3-2), these dense gas tracers are significantly concentrated towards the central $\sim$ 1$"$, suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anti-correlated with the optical one, indicating the existence of dust obscured star formation. The integrated intensity ratios of HCN(4-3)/HCO$^+$(4-3) and HCN(4-3)/CS(7-6) are higher at the AGN position than at the starburst ring, which is consistent to our previous findings (submm-HCN enhancement). However, the HCN(4-3)/HCO$^+$(4-3) ratio at the AGN position of NGC 7469 (1.11$\pm$0.06) is almost half of the corresponding value of the low-luminosity type-1 Seyfert galaxy NGC 1097 (2.0$\pm$0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 ($\sim$ 1.5). Based on these results, we speculate that some other heating mechanisms than X-ray (e.g., mechanical heating due to AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097.

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Local instability signatures in ALMA observations of dense gas in NGC7469

We present an unprecedented measurement of the disc stability and local instability scales in the luminous infrared Seyfert 1 host, NGC7469, based on ALMA observations of dense gas tracers and with a synthesized beam of 165 x 132 pc. While we confirm that non-circular motions are not significant in redistributing the dense interstellar gas in this galaxy, we find compelling evidence that the dense gas is a suitable tracer for studying the origin of its intensely high-mass star forming ring-like structure. Our derived disc stability parameter accounts for a thick disc structure and its value falls below unity at the radii in which intense star formation is found. Furthermore, we derive the characteristic instability scale and find a striking agreement between our measured scale of ~ 180 pc, and the typical sizes of individual complexes of young and massive star clusters seen in high-resolution images.

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No Microwave Flare of Sagittarius A* around the G2 Periastron Passing

In order to explore any change caused by the G2 cloud approaching, we have monitored the flux density of Sgr A* at 22 GHz from Feb. 2013 to Aug. 2014 with a sub-array of Japanese VLBI Network . The observation period included the expected periastron dates. The number of observation epochs was 283 days. We have observed no significant microwave enhancement of Sgr A* in the whole observation period. The average flux density in the period is $S=1.23+/-0.33$ Jy. The average is consistent with the usually observed flux density range of Sgr A* at 22 GHz.

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Hot Ammonia in the Center of the Seyfert 2 galaxy NGC 3079

We present the results of ammonia observations toward the center of NGC 3079. The NH3(J, K) = (1, 1) and (2, 2) inversion lines were detected in absorption with the Tsukuba 32-m telescope, and the NH3(1,1) through (6,6) lines with the VLA, although the profile of NH3(3,3) was in emission in contrast to the other transitions. The background continuum source, whose flux density was ~50 mJy, could not be resolved with the VLA beam of ~< 0."09 x 0."08. All ammonia absorption lines have two distinct velocity components: one is at the systemic velocity and the other is blueshifted, and both components are aligned along the nuclear jets. For the systemic components, the relatively low temperature gas is extended more than the high temperature gas. The blueshifted NH3(3,3) emission can be regarded as ammonia masers associated with shocks by strong winds probably from newly formed massive stars or supernova explosions in dense clouds in the nuclear megamaser disk. Using para-NH3(1,1), (2,2), (4,4) and (5,5) lines with VLA, we derived the rotational temperature Trot = 120 +- 12 K and 157 +- 19 K for the systemic and blueshifted components, respectively. The total column densities of NH3(0,0)-(6,6), assuming Tex ~Trot, were (8.85+-0.70) x 10^16 cm^-2 and (4.47+-0.78) x 10^16 cm-2 for the systemic and blueshifted components, respectively. The fractional abundance of NH3 relative to molecular hydrogen H2 for the systemic and blueshifted was [NH3]/[H2]=1.3x10^-7 and 6.5 x 10^-8, respectively. We also found the F = 4-4 and F = 5-5 doublet lines of OH 2{Pi}3/2 J = 9/2 in absorption, which could be fitted by two velocity components, systemic and redshifted components. The rotational temperature of OH was estimated to be Trot,OH >~ 175 K, tracing hot gas associated with the interaction of the fast nuclear outflow with dense molecular material around the nucleus.

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Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 1097

We present the first 100 pc scale view of the dense molecular gas in the central ~ 1.3 kpc region of the type-1 Seyfert NGC 1097 traced by HCN (J=4-3) and HCO+ (J=4-3) lines afforded with ALMA band 7. This galaxy shows significant HCN enhancement with respect to HCO+ and CO in the low-J transitions, which seems to be a common characteristic in AGN environments. Using the ALMA data, we study the characteristics of the dense gas around this AGN and search for the mechanism of HCN enhancement. We find a high HCN (J=4-3) to HCO+ (J=4-3) line ratio in the nucleus. The upper limit of the brightness temperature ratio of HCN (v2=1^{1f}, J=4-3) to HCN (J=4-3) is 0.08, which indicates that IR pumping does not significantly affect the pure rotational population in this nucleus. We also find a higher HCN (J=4-3) to CS (J=7-6) line ratio in NGC 1097 than in starburst galaxies, which is more than 12.7 on the brightness temperature scale. Combined from similar observations from other galaxies, we tentatively suggest that this ratio appears to be higher in AGN-host galaxies than in pure starburst ones similar to the widely used HCN to HCO+ ratio. LTE and non-LTE modeling of the observed HCN and HCO+ lines using J=4-3 and 1-0 data from ALMA, and J=3-2 data from SMA, reveals a high HCN to HCO+ abundance ratio (5 < [HCN]/[HCO+] < 20: non-LTE analysis) in the nucleus, and that the high-J lines (J=4-3 and 3-2) are emitted from dense (10^{4.5} < n_H2 [/cc] < 10^6), hot (70 < Tkin [K] < 550) regions. Finally we propose that the high temperature chemistry is more plausible to explain the observed enhanced HCN emission in NGC 1097 than the pure gas phase PDR/XDR chemistry.

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ALMA follows streaming of dense gas down to 40 pc from the supermassive black hole in NGC1097

We present a kinematic analysis of the dense molecular gas in the central 200 parsecs of the nearby galaxy NGC1097, based on Cycle 0 observations with the Atacama Large Millimeter/sub-millimeter Array (ALMA). We use the HCN(4-3) line to trace the densest interstellar molecular gas, and quantify its kinematics, and estimate an inflow rate for the molecular gas. We find a striking similarity between the ALMA kinematic data and the analytic spiral inflow model that we have previously constructed based on ionized gas velocity fields on larger scales. We are able to follow dense gas streaming down to 40 pc distance from the supermassive black hole in this Seyfert 1 galaxy. In order to fulfill marginal stability, we deduce that the dense gas is confined to a very thin disc, and we derive a dense gas inflow rate of 0.09 Msun/yr at 40 pc radius. Combined with previous values from the Ha and CO gas, we calculate a combined molecular and ionized gas inflow rate of 0.2 Msun/yr at 40 pc distance from the central supermassive black hole of NGC1097.

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Water-Vapor Maser Disk at the Nucleus of the Seyfert 2 Galaxy IC 2560 and its Distance

We present the results of single-dish and VLBI observations for the water-vapor masers at the nucleus of the Seyfert 2, IC 2560. We monitored velocities of the maser features with the 45-m telescope of the Nobeyama Radio Observatory. Using the data of 1995--2006, the velocity drift rate was detected to be a = +2.57 +/- 0.04 km/s/yr on the average for 6 systemic features. The Very Long Baseline Array (VLBA) with the Very Large Array (VLA) firstly detected a red-shifted and a blue-shifted maser features of IC 2560, in addition to systemic maser features and a continuum component. We propose a maser disk in the nuclear region. The systemic and red-shifted features are emitted from a nearly edge-on disk with the position angle of PA = -46 deg, which is almost perpendicular to the galactic disk. Assuming the Keplerian rotation, the radii of the maser disk are r = 0.087--0.335 pc, and the thickness is 2H <= 0.025 pc. The binding mass is 3.5 x 10^6 Msun at a distance of D = 26 Mpc, and the mean volume density within the inner radius is 1.3 x 10^9 Msun/pc^3, strongly suggesting a massive black hole at the center. A continuum component was detected at the 0.2 pc southwest of the disk center, and considered as a jet ejected from the nucleus, with an angle of 70 deg from the disk. The blue-shifted maser feature is located on the continuum component, being interpreted to be a "jet maser". The distance to IC 2560 is estimated to be D = 31^{+12}_{-14} Mpc from the geometry of the maser disk and the velocity drift rate.

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AGN disks and black holes on the weighting scales

We exploit our formula for the gravitational potential of finite size, power-law disks to derive a general expression linking the mass of the black hole in active galactic nuclei (AGN), the mass of the surrounding disk, its surface density profile (through the power index s), and the differential rotation law. We find that the global rotation curve v(R) of the disk in centrifugal balance does not obey a power law of the cylindrical radius R (except in the confusing case s = -2 that mimics a Keplerian motion), and discuss the local velocity index. This formula can help to understand how, from position-velocity diagrams, mass is shared between the disk and the black hole. To this purpose, we have checked the idea by generating a sample of synthetic data with different levels of Gaussian noise, added in radius. It turns out that, when observations are spread over a large radial domain and exhibit low dispersion (standard deviation less than 10% typically), the disk properties (mass and s-parameter) and black hole mass can be deduced from a non linear fit of kinematic data plotted on a (R, Rv 2)-diagram. For a deviation higher than 10%, masses are estimated fairly well from a linear regression (corresponding to the zeroth-order treatment of the formula), but the power index s is no longer accessible. We have applied the model to 7 AGN disks whose rotation has already been probed through water maser emission. For NGC3393 and UGC3789, the masses seem well constrained through the linear approach. For IC1481, the power-law exponent s can even be deduced. Because the model is scale-free, it applies to any kind of star/disk system. Extension to disks around young stars showing deviation from Keplerian motion is thus straightforward.

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VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars

We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey (SDSS) Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network (JVN). We aimed at selecting BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 10^5 K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four inverted-spectrum sources, which are interpreted as Doppler-beamed, pole-on-viewed relativistic jet sources or young radio sources: single edge-on geometry cannot describe all BAL quasars. We discuss the implications of the OCTAVE observations for investigations for the orientation and evolutionary stage of BAL quasars.

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