分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present new spectroscopic observations of Lyman-$\alpha$ (Ly$\alpha$) Blob 2 ($z \sim$ 3.1). We observed extended Ly$\alpha$ emission in three distinct regions, where the highest Ly$\alpha$ surface brightness (SB) center is far away from the known continuum sources. We searched through the MOSFIRE slits that cover the high Ly$\alpha$ SB regions, but were unable to detect any significant nebular emission near the highest SB center. We further mapped the flux ratio of the blue peak to the red peak and found it is anti-correlated with Ly$\alpha$ SB with a power-law index of $\sim$ -0.4. We used radiative transfer models with both multiphase, clumpy and shell geometries and successfully reproduced the diverse Ly$\alpha$ morphologies. We found that most spectra suggest outflow-dominated kinematics, while 4/15 spectra imply inflows. A significant correlation exists between parameter pairs, and the multiphase, clumpy model may alleviate previously reported discrepancies. We also modeled Ly$\alpha$ spectra at different positions simultaneously and found that the variation of the inferred clump outflow velocities can be approximately explained by line-of-sight projection effects. Our results support the `central powering + scattering' scenario, i.e. the Ly$\alpha$ photons are generated by a central powering source and then scatter with outflowing, multiphase HI gas while propagating outwards. The infalling of cool gas near the blob outskirts shapes the observed blue-dominated Ly$\alpha$ profiles, but its energy contribution to the total Ly$\alpha$ luminosity is less than 10%, i.e. minor compared to the photo-ionization by star-forming galaxies and/or AGNs.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Satoshi Kikuta
Yuichi Matsuda
Shigeki Inoue
Charles C. Steidel
Renyue Cen
Zheng Zheng
Hidenobu Yajima
Rieko Momose
Masatoshi Imanishi
Yutaka Komiyama
摘要： We present UV and Ly$\alpha$ radial surface brightness (SB) profiles of Ly$\alpha$ emitters (LAEs) at $z=2.84$ detected with the Hyper Suprime-Cam (HSC) on the Subaru Telescope. The depth of our data, together with the wide field coverage including a protocluster, enable us to study the dependence of Ly$\alpha$ halos (LAHs) on various galaxy properties, including Mpc-scale environments. UV and Ly$\alpha$ images of 3490 LAEs are extracted, and stacking the images yields SB sensitivity of $\sim1\times10^{-20}\mathrm{~erg~s^{-1}~cm^{-2}~arcsec^{-2}}$ in Ly$\alpha$, reaching the expected level of optically thick gas illuminated by the UV background at $z\sim3$. Fitting of the two-component exponential function gives the scale-lengths of $1.56\pm0.01$ and $10.4\pm0.3$ pkpc. Dividing the sample according to their photometric properties, we find that while the dependence of halo scale-length on environment outside of the protocluster core is not clear, LAEs in the central regions of protoclusters appear to have very large LAHs which could be caused by combined effects of source overlapping and diffuse Ly$\alpha$ emission from cool intergalactic gas permeating the forming protocluster core irradiated by active members. For the first time, we identify ``UV halos'' around bright LAEs which are probably due to a few lower-mass satellite galaxies. Through comparison with recent numerical simulations, we conclude that, while scattered Ly$\alpha$ photons from the host galaxies are dominant, star formation in satellites evidently contributes to LAHs, and that fluorescent Ly$\alpha$ emission may be boosted within protocluster cores at cosmic noon and/or near bright QSOs.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Minhee Hyun
Myungshin Im
Ian R. Smail
William D. Cotton
Jack E. Birkin
Satoshi Kikuta
Hyunjin Shim
Christopher N. A. Willmer
James J. Condon
Rogier A. Windhorst
Seth H. Cohen
Rolf A. Jansen
Chun Ly
Yuichi Matsuda
Giovanni G. Fazio
A. M. Swinbank
Haojing Yan
摘要： The James Webb Space Telescope Time-Domain Field (JWST-TDF) is an $\sim$14$'$ diameter field near the North Ecliptic Pole that will be targeted by one of the JWST Guaranteed Time Observations programs. Here, we describe our James Clerk Maxwell Telescope SCUBA-2 850 $\mu$m imaging of the JWST-TDF and present the submillimeter source catalog and properties. We also present a catalog of radio sources from Karl J. Jansky Very Large Array 3 GHz observations of the field. These observations were obtained to aid JWST's study of the dust-obscured galaxies that contribute significantly to the cosmic star formation at high redshifts. Our deep 850 $\mu$m map covers the JWST TDF at a noise level of $\sigma_{850}$ = 1.0 mJy beam$^{-1}$, detecting 83/31 sources in the main/supplementary signal-to-noise ratio (S/N $>$ 4 / S/N = 3.5 - 4) sample respectively. The 3 GHz observations cover a 24$'$ diameter field with a 1 $\sigma$ noise of 1$\mu$Jy beam$^{-1}$ at a 0$.\!\!^{\prime\prime}$7 FWHM. We identified eighty-five 3 GHz counterparts to sixty-six 850 $\mu$m sources and then matched these with multiwavelength data from the optical to the mid-infrared wave bands. We performed spectral energy distribution fitting for 61 submillimeter galaxies (SMGs) matched with optical/near-infrared data, and found that SMGs at S/N $>$ 4 have a median value of $z_{phot} = $2.22 $\pm$ 0.12, star formation rates of 300 $\pm$ 40 M$_{\odot}\,{\rm yr^{-1}}$ (Chabrier initial mass function), and typical cold dust masses of 5.9 $\pm$ 0.7 $ \times$ 10$^{8} $M$_{\odot}$, in line with bright SMGs from other surveys. The large cold dust masses indicate correspondingly large cool gas masses, which we suggest are a key factor necessary to drive the high star formation rates seen in this population
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shenli Tang
John D. Silverman
Xuheng Ding
Junyao Li
Khee-Gan Lee
Michael A. Strauss
Andy Goulding
Malte Schramm
Lalitwadee Kawinwanichakij
J. Xavier Prochaska
Joseph F. Hennawi
Masatoshi Imanishi
Kazushi Iwasawa
Yoshiki Toba
Issha Kayo
Masamune Oguri
Yoshiki Matsuoka
Kohei Ichikawa
Tilman Hartwig
Nobunari Kashikawa
摘要： We report on a spectroscopic program to search for dual quasars using Subaru Hyper Suprime-Cam (HSC) images of SDSS quasars which represent an important stage during galaxy mergers. Using Subaru/FOCAS and Gemini-N/GMOS, we identify three new physically associated quasar pairs having projected separations less than 20 kpc, out of 26 observed candidates. These include the discovery of the highest redshift ($z=3.1$) quasar pair with a separation $<$ 10 kpc. Based on the sample acquired to date, the success rate of identifying physically associated dual quasars is $19\%$ when excluding stars based on their HSC colors. Using the full sample of six spectroscopically confirmed dual quasars, we find that the black holes in these systems have black hole masses ($M_{BH} \sim 10^{8-9}M_{\odot}$) similar to single SDSS quasars as well as their bolometric luminosities and Eddington ratios. We measure the stellar mass of their host galaxies based on 2D image decomposition of the five-band ($grizy$) optical emission and assess the mass relation between supermassive black holes (SMBHs) and their hosts. Dual SMBHs appear to have elevated masses relative to their host galaxies. Thus mergers may not necessarily align such systems onto the local mass relation, as suggested by the Horizon-AGN simulation. This study suggests that dual luminous quasars are triggered prior to the final coalescence of the two SMBHs, resulting in early mass growth of the black holes relative to their host galaxies.
点击量
待评议
点击量
下载量
评论
