We present Expanded Very Large Array and Arecibo observations of two lensed submm galaxies at z~2.5, in order to search for redshifted 22.235 GHz water megamaser emission. Both SMM J14011+0252 and SMM J16359+6612 have multi-wavelength characteristics consistent with ongoing starburst activity, as well as CO line emission indicating the presence of warm molecular gas. Our observations do not reveal any evidence for H2O megamaser emission in either target, while the lensing allows us to obtain deep limits to the H_2O line luminosities, L(H2O) < 7470 Lsun (3-sigma) in the case of SMM J14011+0252, and L(H2O) < 1893 Lsun for SMM J16359+6612, assuming linewidths of 80 km/s. Our search for, and subsequent non-detection of H2O megamaser emission in two strongly lensed starburst galaxies, rich in gas and dust, suggests that such megamaser emission is not likely to be common within the unlensed population of high-redshift starburst galaxies. We use the recent detection of strong H2O megamaser emission in the lensed quasar, MG J0414+0534 at z = 2.64 to make predictions for future EVLA C-band surveys of H2O megamaser emission in submm galaxies hosting AGN.
A Chandra observation of the ultraluminous infrared galaxy IRAS 19254--7245 (the Superantennae): X-ray emission from the Compton-thick AGN and the diffuse starburst
我们提出了一个IRAS 19254- 7245的{ \it Chandra}观测,它是一个邻近的ULIRG,也被称为{ \it the Superantennas}。高空间分辨率的{ \it钱德拉}使我们能够解开第一次从嵌入康普顿厚的活动星系核的弥漫星暴辐射。活动星系核的2-10 keV辐射谱符合平坦的幂律($Γ=1.3$)和类He的Fe K $α$谱线,EW $\sim$ 1.5 keV,与以前的观测结果一致。Fe K $α$谱线轮廓可以被解析为中性6.4 keV谱线和电离6.7 keV(类He)或6.9 keV(类H)谱线的混合。与以前的{ \it XMM-Newton}和{ \it suzaku}观测相比,检测到了变化,证明了铁谱线发射的紧凑尺寸。我们拟合的光谱的星系尺度扩展发射不包括活动星系核和其他亮点源的软热分量与kT~0.8 keV。扩展辐射的亮度比活动星系核的亮度低一个数量级。扩展辐射的基本物理和结构性质与星暴驱动的星系风完全一致(不需要AGN的反馈)。在南核以南8 \arcsec处检测到候选超亮X射线源。如果发射是各向同性的,并且与超天线有关,那么这个离核点源的0.3-10 keV光度为~ $6\times 10^{40}$ erg s $^{-1}$。
The Complex Structure of the Multi-Phase Galactic Wind in a Starburst Merger
通过Na I D $λλ5890, 5896$吸收线偶线,在许多超亮红外星系(ULIRGs)中观测到了中性外流。首次利用Gemini North上的积分场单元(IFU)对ULIRG(F10565+2448)中的冷中性外流进行了二维运动学分析,并观测了Na I D特征。同时,我们用[NII]和H $α$的发射线绘制了电离流出图。我们发现一个系统的旋转曲线,这是一致的分子盘从以前的CO观测确定的旋转。吸收线显示出核流出的证据,径向范围至少为3千秒差距,与以前的观测结果一致。Na I D线的强度有很强的,空间分辨的相关性与变红,这表明尘埃是存在于流出。令人惊讶的是,中性气体的流出速度显示出强烈的不对称性,其形式为与盘旋转符号相反的主轴梯度。这与随星系旋转的夹带物质或倾斜的短轴流出不一致。我们假设这种不寻常的行为是由于周围气体分布的不对称性。我们还看到不对称的电离流出的证据,在发射线速度图,这似乎是从中性流出解耦。我们的研究结果加强了这样一个假设,即ULIRG外流在形态上不同于那些在更安静的盘星系。
We present radio observations of ultraluminous infrared galaxies (ULIRGs) using the Giant Metrewave Radio Telescope (GMRT) and combine them with archival multi-frequency observations to understand whether ULIRGs are the progenitors of the powerful radio loud galaxies in the local Universe. ULIRGs are characterized by large infrared luminosities ($L_{IR}>$10$^{12}$L$\odot$), large dust masses ($\sim10^{8}M_{\odot}$) and vigorous star formation (star formation rates $\sim$10-100 $M_{\odot}~$yr$^{-1}$). Studies show that they represent the end stages of mergers of gas-rich spiral galaxies. Their …