We present the results of observations of the very low surface brightness (VLSB) dwarf galaxy SDSS J092609.45+334304.1 with extreme parameters which indicate its unevolved status. Namely, its value of O/H, derived as an average of that in two adjacent HII regions at the NE edge of the disc, corresponds to the parameter 12+log(O/H)=7.12+-0.02, which is amongst two lowest known. The total HI flux measurement obtained with the Nancay Radio Telescope and the photometric results imply that the galaxy ratio M(HI)/L_B ~3.0, is among the top known in the Local Volume. The galaxy is situated in the region of a nearby underdense region known as the Lynx-Cancer void, where other, unevolved galaxies, including DDO 68, HS 0832+3542 and SAO 0822+3545, are known to be present. The total mass of this almost edge-on VLSB galaxy is ~8.3 times larger than its baryonic mass, implying the dynamical dominance of Dark Matter (DM) halo. The (u-g), (g-r) colours of outer parts of this galaxy are consistent with the ages of its main stellar population of 1--3 Gyr. Thanks to the galaxy isolation, the small effect of current or recent star formation (SF), its proximity and rather large HI flux (~2.5 Jy km/s), this VLSB dwarf is a good laboratory for the detailed study of DM halo properties through HI kinematics and the star formation processes in very metal-poor low surface density environment. This finding, along with the discovery of other unusual dwarf galaxies in this void, provides evidence for the relation between galaxy evolution and its very low-density environment for the baryonic mass range of 10^{8} to 10^{9} Mo. This relation seems to be consistent with that expected in the LambdaCDM models of galaxy and structure formation.
SDSS J133401.39+331534.3: A New Subarcsecond Gravitationally Lensed Quasar
z = 2.426的类星体SDSS J133401.39+331534.3是一个双像引力透镜类星体,像间距为0.833。该物体首先在斯隆数字巡天类星体透镜搜索中被确定为透镜类星体候选者,然后通过斯巴鲁和夏威夷大学2.2米望远镜的后续观测确认为透镜系统。根据类星体光谱中的吸收线以及星系的颜色,我们估计透镜星系的红移为0.557。特别是,我们观察了斯巴鲁望远镜AO188自适应光学与激光导星,以获得准确的天体测量,这很好地证明了有用的激光导星自适应光学成像研究强透镜系统。我们的质量模型与改进的天体测量意味着附近的明亮星系$\sim 4"$除了透镜星系很可能会影响透镜的潜力。
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VIII. Deconvolution of high resolution near-IR images and simple mass models for 7 gravitationally lensed quasars
A Census of Broad-Line Active Galactic Nuclei in Nearby Galaxies: Coeval Star Formation and Rapid Black Hole Growth
本文首次给出了宽线活动星系核(AGN)频率与邻近(0.01 < z < 0.11)星系的主星系颜色和恒星质量的定量统计图。斯隆数字巡天(SDSS)的孔径测光和z波段浓度测量被用来解开活动星系核和星系发射,从而估计未受污染的星系静止框架颜色,光度和恒星质量。宽线活动星系核在恒星质量一定的情况下,分布在整个蓝色星云和绿色山谷中,在静止(红色序列)星系中更为罕见。这与已发表的较弱窄线活动星系核的宿主星系性质相反,表明宽线活动星系核发生在星系演化的不同阶段。更明亮的宽线活动星系核有更蓝的宿主星系,即使在固定质量下,这表明为核活动提供燃料的过程也有效地形成了恒星。这些数据有利于同时为恒星形成活动和快速超大质量黑洞吸积提供燃料的过程。如果活动星系核对邻近宇宙中的宿主星系产生反馈,那么星系范围内的猝灭的证据必须延迟到活动星系核的宽线阶段之后。
Unveiling Electron Density Profile in Nearby Galaxies using SDSS MaNGA
Indian Institute of Technology Delhi(印度理工学院德里分校);National Centre for Radio Astrophysics, Tata Institute of Fundamental Research(塔塔基础研究所国家射电天体物理中心);Universidad Complutense de Madrid(马德里康普顿斯大学)
The Baryon Acoustic Oscillation (BAO) scale in the clustering of galaxies is a powerful standard ruler to measure cosmological distances and determine the geometry of the Universe. Past surveys have detected the BAO feature in the clustering of different galaxy samples, most of them composed of redder, quiescent galaxies and bluer, star-forming ones out to redshift $z\sim1$. Besides these targets, new upcoming surveys will observe high-redshift galaxies with bright nebular emission lines out to $z\sim2$, quasars and Lyman-$α$ quasars at $z\gt 2$. All these different galaxy targets will be used…