We have compared the TeV gamma-rays with the new 12CO J=2-1 data toward HESS J1745-303 in the Galactic center and confirmed that the molecular gas MG358.9-0.5 toward (l, b)=(358.9, -0.5 at VLSR=-100-0 km s-1 shows a reasonable positional agreement wi
th the primary peak (northern part) of the gamma-ray source. For the southern part of HESS J1745-303, we see no CO counterpart, whereas the HI gas in the Parkes 21 cm HI dataset shows a possible counterpart to the gamma-ray source. This HI gas may be optically thick as supported by the HI line shape similar to the optically thick 12CO. We estimate the total mass of interstellar protons including both the molecular and atomic gas to be 2x10^6 Mo and the cosmic-ray proton energy to be 6x10^{48} ergs in the hadronic scenario. We discuss possible origins of the cosmic-ray protons including the nearby SNR G359.1-0.5. The SNR may be able to explain the northern gamma-ray source but the southern source seems to be too far to be energized by the SNR. As an alternative, we argue that the second-order Fermi acceleration in the inter-clump space surrounded by randomly moving high-velocity clumps may offer a possible mechanism to accelerate protons. The large turbulent motion with velocity dispersion of ~15 km s-1 has energy density two orders of magnitude higher than in the solar vicinity and is viable as the energy source.
We have carried out 12CO(J =2-1) and 12CO(J =3-2) observations at spatial resolutions of 1.0-3.8 pc toward the entirety of loops 1 and 2 and part of loop 3 in the Galactic center with NANTEN2 and ASTE. These new results revealed detailed distribution
s of the molecular gas and the line intensity ratio of the two transitions, R3-2/2-1. In the three loops, R3-2/2-1 is in a range from 0.1 to 2.5 with a peak at ~ 0.7 while that in the disk molecular gas is in a range from 0.1 to 1.2 with a peak at 0.4. This supports that the loops are more highly excited than the disk molecular gas. An LVG analysis of three transitions, 12CO J =3-2 and 2-1 and 13CO J =2-1, toward six positions in loops 1 and 2 shows density and temperature are in a range 102.2 - 104.7 cm-3 and 15-100 K or higher, respectively. Three regions extended by 50-100 pc in the loops tend to have higher excitation conditions as characterized by R3-2/2-1 greater than 1.2. The highest ratio of 2.5 is found in the most developed foot points between loops 1 and 2. This is interpreted that the foot points indicate strongly shocked conditions as inferred from their large linewidths of 50-100 km s-1, confirming the suggestion by Torii et al. (2010b). The other two regions outside the foot points suggest that the molecular gas is heated up by some additional heating mechanisms possibly including magnetic reconnection. A detailed analysis of four foot points have shown a U shape, an L shape or a mirrored-L shape in the b-v distribution. It is shown that a simple kinematical model which incorporates global rotation and expansion of the loops is able to explain these characteristic shapes.
Fukui et al. (2006) discovered two huge molecular loops in the Galactic center located in (l, b) ~ (355 deg-359 deg, 0 deg-2 deg) in a large velocity range of -180-40 km s^-1. Following the discovery, we present detailed observational properties of t
he two loops based on NANTEN 12CO(J=1-0) and 13CO(J=1-0) datasets at 10 pc resolution including a complete set of velocity channel distributions and comparisons with HI and dust emissions as well as with the other broad molecular features. We find new features on smaller scales in the loops including helical distributions in the loop tops and vertical spurs. The loops have counterparts of the HI gas indicating that the loops include atomic gas. The IRAS far infrared emission is also associated with the loops and was used to derive an X-factor of 0.7(+/-0.1){times}10^20 cm^-2 (K km s^-1)^-1 to convert the 12CO intensity into the total molecular hydrogen column density. From the 12CO, 13CO, H I and dust datasets we estimated the total mass of loops 1 and 2 to be ~1.4 {times} 106 Msun and ~1.9 {times} 10^6 Msun, respectively, where the H I mass corresponds to ~10-20% of the total mass and the total kinetic energy of the two loops to be ~10^52 ergs. An analysis of the kinematics of the loops yields that the loops are rotating at ~47 km s-1 and expanding at ~141 km s^-1 at a radius of 670 pc from the center. Fukui et al. (2006) presented a model that the loops are created by the magnetic flotation due to the Parker instability with an estimated magnetic field strength of ~150 {mu}G. We present comparisons with the recent numerical simulations of the magnetized nuclear disk by Machida et al. (2009) and Takahashi et al. (2009) and show that the theoretical results are in good agreements with the observations. The helical distributions also suggest that some magnetic instability plays a role similarly to the solar helical features.
We have discovered a molecular dome-like feature towards $355^{circ} leq l leq 359^{circ}$ and $0^{circ} leq b leq 2^{circ}$. The large velocity dispersions of 50--100 km s$^{-1}$ of this feature are much larger than those in the Galactic disk and in
dicate that the feature is located in the Galactic center, probably within $sim1$ kpc of Sgr A$^{*}$. The distribution has a projected length of $sim600$ pc and height of $sim300$ pc from the Galactic disk and shows a large-scale monotonic velocity gradient of $sim130$ km s $^{-1}$ per $sim600$ pc. The feature is also associated with HI gas having a more continuous spatial and velocity distribution than that of $^{12}$CO. We interpret the feature as a magnetically floated loop similar to loops 1 and 2 and name it loop 3. Loop 3 is similar to loops 1 and 2 in its height and length but is different from loops 1 and 2 in that the inner part of loop 3 is filled with molecular emission. We have identified two foot points at the both ends of loop 3. HI, $^{12}$CO and $^{13}$CO datasets were used to estimate the total mass and kinetic energy of loop 3 to be $sim3.0 times 10^{6} Mo$ and $sim1.7 times 10^{52}$ ergs. The huge size, velocity dispersions and energy are consistent with the magnetic origin the Parker instability as in case of loops 1 and 2 but is difficult to be explained by multiple stellar explosions. We argue that loop 3 is in an earlier evolutionary phase than loops 1 and 2 based on the inner-filled morphology and the relative weakness of the foot points. This discovery indicates that the western part of the nuclear gas disk of $sim1$ kpc radius is dominated by the three well-developed magnetically floated loops and suggests that the dynamics of the nuclear gas disk is strongly affected by the magnetic instabilities.
