اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدALMA observations of HCN and HCO+ outflows in the merging galaxy NGC 3256
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We report ~2 resolution Atacama Large Millimeter/submillimeter Array observations of the HCN(1-0), HCO+(1-0), CO(1-0), CO(2-1), and CO(3-2) lines towards the nearby merging double-nucleus galaxy NGC 3256. We find that the high density gas outflow traced in HCN(1-0) and HCO+(1-0) emission is co-located with the diffuse molecular outflow emanating from the southern nucleus, where a low-luminosity active galactic nucleus (AGN) is believed to be the dominant source of the far-infrared luminosity. On the other hand, the same lines were undetected in the outflow region associated with the northern nucleus, whose primary heating source is likely related to starburst activity without obvious signs of AGN. Both HCO+(1-0)/CO(1-0) line ratio (i.e. dense gas fraction) and the CO(3-2)/CO(1-0) line ratio are larger in the southern outflow (0.20$pm$0.04 and 1.3$pm$0.2, respectively) than in the southern nucleus (0.08$pm$0.01, 0.7$pm$0.1, respectively). By investigating these line ratios for each velocity component in the southern outflow, we find that the dense gas fraction increases and the CO(3-2)/CO(1-0) line ratio decreases towards the largest velocity offset. This suggests the existence of a two-phase (diffuse and clumpy) outflow. One possible scenario to produce such a two-phase outflow is an interaction between the jet and the interstellar medium, which possibly triggers shocks and/or star formation associated with the outflow.
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We report ALMA and SMA observations of the luminous infrared merger NGC 3256, the most luminous galaxy within z=0.01. Both of the two merger nuclei separated by 5 (0.8 kpc) on the sky have a compact concentration of molecular gas, i.e., nuclear disks
with Sigma_mol > 10^3 Msun pc^-2. The one at the northern nucleus is face-on while the southern nuclear disk is almost edge-on. The northern nucleus is more massive and has molecular arcs and spiral arms around. The high-velocity molecular gas previously found in the system is resolved to two molecular outflows associated with each of the two nuclei. The molecular outflow from the northern nuclear disk is part of a starburst-driven superwind seen nearly pole on. Its maximum velocity is >750 km/s and its mass outflow rate is estimated to be > 60 Msun/yr for a conversion factor N_{H_2}/I_{CO(1-0)}=1x10^20 cm^-2/(K km/s). The outflow from the southern nucleus is a highly collimated bipolar molecular jet seen nearly edge-on. Its line-of-sight velocity increases with distance out to 300 pc from the southern nucleus. Its maximum de-projected velocity is ~2000 km/s for the estimated inclination and should exceed 1000 km/s even allowing for its uncertainty. The mass outflow rate is estimated to be >50 Msun/yr for this outflow. There are possible signs that this southern outflow has been driven by a bipolar radio jet from an AGN that became inactive very recently. The sum of these outflow rates, although subject to the uncertainty in the molecular mass estimate, either exceeds or compares to the total star formation rate in NGC 3256. The feedback from nuclear activities in the form of molecular outflows is therefore significant in the gas consumption budget, and hence evolution, of this luminous infrared galaxy. (abridged)
In external galaxies, molecular composition may be influenced by extreme environments such as starbursts and galaxy mergers. To study such molecular chemistry, we observed the luminous-infrared galaxy and merger NGC 3256 using the Atacama Large Milli
meter/sub-millimeter Array. We covered most of the 3-mm and 1.3-mm bands for a multi-species, multi-transition analysis. We first analyzed intensity ratio maps of selected lines such as HCN/HCO$^+$, which shows no enhancement at an AGN. We then compared the chemical compositions within NGC 3256 at the two nuclei, tidal arms, and positions with influence from galactic outflows. We found the largest variation in SiO and CH$_3$OH, species that are likely to be enhanced by shocks. Next, we compared the chemical compositions in the nuclei of NGC 3256, NGC 253, and Arp 220; these galactic nuclei have varying star formation efficiencies. Arp 220 shows higher abundances of SiO and HC$_3$N than NGC 3256 and NGC 253. Abundances of most species do not show strong correlation with the star formation efficiencies, although the CH$_3$CCH abundance seems to have a weak positive correlation with the star formation efficiency. Lastly, the chemistry of spiral arm positions in NGC 3256 is compared with that of W 51, a Galactic molecular cloud complex in a spiral arm. We found higher fractional abundances of shock tracers, and possibly also higher dense gas fraction in NGC 3256 compared with W 51.
We present the results of our ALMA observations of three AGN-dominated nuclei in optical Seyfert 1 galaxies (NGC 7469, I Zw 1, and IC 4329 A) and eleven luminous infrared galaxies (LIRGs) with various levels of infrared estimated energetic contributi
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We present the results of high spatial resolution HCO$^{+}$($1-0$) and HCN($1-0$) observations of N55 south region (N55-S) in the Large Magellanic Cloud (LMC), obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). N55-S is a relative
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