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Register a new userALMA Observations of the Sub-kpc Structure of the Host Galaxy of a z= 6.5 Lensed Quasar: A Rotationally-Supported Hyper-Starburst System at the Epoch of Reionization
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We report ALMA observations of the dust continuum and {cii} emission of the host galaxy of J0439+1634, a gravitationally lensed quasar at $z=6.5$. Gravitational lensing boosts the source-plane resolution to $sim0farcs15$ $(sim0.8text{ kpc})$. The lensing model derived from the ALMA data is consistent with the fiducial model in citet{fan19} based on {it HST} imaging. The host galaxy of J0439+1634 can be well-fitted by a Sersic profile consistent with an exponential disk, both in the far-infrared (FIR) continuum and the {cii} emission. The overall magnification is $4.53pm0.05$ for the continuum and $3.44pm0.05$ for the {cii} line. The host galaxy of J0439+1634 is a compact ultra-luminous infrared galaxy, with a total star formation rate (SFR) of $1.56times10^{3}M_odot/text{year}$ after correcting for lensing and an effective radius of $0.74$ kpc. The resolved regions in J0439+1634 follow the ``{cii} deficit, where the {cii}-to-FIR ratio decreases with FIR surface brightness. The reconstructed velocity field of J0439+1634 appears to be rotation-like. The maximum line-of-sight rotation velocity of 130 km/s at a radius of 2 kpc. However, our data cannot be fit by an axisymmetric thin rotating disk, and the inclination of the rotation axis, $i$, remains unconstrained. We estimate the dynamical mass of the host galaxy to be $7.9sin^{-2}(i)times10^{9}M_odot$. J0439+1634 is likely to have a high gas-mass fraction and an oversized SMBH compared to local relations. The SFR of J0439+1634 reaches the maximum possible values, and the SFR surface density is close to the highest value seen in any star-forming galaxy currently known in the universe.
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We present ALMA 2-mm continuum and CO (2-1) spectral line imaging of the gravitationally lensed z=0.654 star-forming/quasar composite RX J1131-1231 at 240-400 mas angular resolution. The continuum emission is found to be compact and coincident with the optical emission, whereas the molecular gas forms a complete Einstein ring, which shows strong differential magnification. The de-lensed source structure is determined on 400-pc resolution using a visibility-fitting lens modelling technique. The reconstructed molecular gas velocity-field is consistent with a rotating disk with a maximum rotational velocity of 280 km/s. From dynamical model fitting we find an enclosed mass M(r<5 kpc)=(1.46+/-0.31)*10^11 M_sol. The molecular gas distribution is highly structured, with clumps that are co-incident with higher gas velocity dispersion regions 40-50 km/s and with the intensity peaks in the optical emission, which are associated with sites of on-going turbulent star-formation. The peak in the CO (2-1) distribution is not co-incident with the AGN, where there is a paucity of molecular gas emission, possibly due to radiative feedback from the central engine. The intrinsic molecular gas luminosity is L_CO=(1.2+/-0.3)*10^10 K km/s pc^2 and the inferred gas mass is M(H2)=(8.3+/-3.0)*10^10 M_sol, which given its dynamical mass is consistent with a CO-H2 conversion factor of alpha = 5.5+/-2.0 M_solar(K km/s pc^2)^-1. This suggests that the star-formation efficiency is dependent on the host galaxy morphology as opposed to the nature of the AGN. The far-infrared continuum spectral energy distribution shows evidence for heated dust, equivalent to an obscured star-formation rate of SFR=69^(+41)_(-25)*(7.3/u_IR)M_sol/yr, which demonstrates the composite star-forming/AGN nature of this system. RX J1131-1231
A significant minority of high redshift radio galaxy (HzRG) candidates show extremely red broad band colours and remain undetected in emission lines after optical `discovery spectroscopy. In this paper we present deep GTC optical imaging and spectroscopy of one such radio galaxy, 5C 7.245, with the aim of better understanding the nature of these enigmatic objects. Our g-band image shows no significant emission coincident with the stellar emission of the host galaxy, but does reveal faint emission offset by ~3 (26 kpc) therefrom along a similar position angle to that of the radio jets, reminiscent of the `alignment effect often seen in the optically luminous HzRGs. This offset g-band source is also detected in several UV emission lines, giving it a redshift of 1.609, with emission line flux ratios inconsistent with photoionization by young stars or an AGN, but consistent with ionization by fast shocks. Based on its unusual gas geometry, we argue that in 5C 7.245 we are witnessing a rare (or rarely observed) phase in the evolution of quasar hosts when stellar mass assembly, accretion onto the back hole, and powerful feedback activity has eradicated its cold gas from the central ~20 kpc, but is still in the process of cleansing cold gas from its extended halo.
We present ALMA band-7 data of the [CII] $lambda157.74,mu{rm m}$ emission line and underlying far-infrared (FIR) continuum for twelve luminous quasars at $z simeq 4.8$, powered by fast-growing supermassive black holes (SMBHs). Our total sample consists of eighteen quasars, twelve of which are presented here for the first time. The new sources consists of six Herschel/SPIRE detected systems, which we define as FIR-bright sources, and six Herschel/SPIRE undetected systems, which we define as FIR-faint sources. We determine dust masses for the quasars hosts of $M_{dust} le 0.2-25.0times 10^8 M_{odot}$, implying ISM gas masses comparable to the dynamical masses derived from the [CII] kinematics. It is found that on average the MgII line is blueshifted by $sim 500,{rm km,s}^{-1}$ with respect to the [CII] emission line, which is also observed when complementing our observations with data from the literature. We find that all of our FIR-bright subsample and most of the FIR-faint objects lie above the main sequence of star forming galaxies at $z sim 5$. We detect companion sub-millimeter galaxies (SMGs) for two sources, both FIR-faint, with a range of projected distances of $sim20-60$ kpc and with typical velocity shifts of $left|Delta vright| lesssim200,{rm km,s}^{-1}$ from the quasar hosts. Of our total sample of eighteen quasars, 5/18 are found to have dust obscured starforming companions.
Strong gravitational lensing provides a powerful probe of the physical properties of quasars and their host galaxies. A high fraction of the most luminous high-redshift quasars was predicted to be lensed due to magnification bias. However, no multiple imaged quasar was found at z>5 in previous surveys. We report the discovery of J043947.08+163415.7, a strongly lensed quasar at z=6.51, the first such object detected at the epoch of reionization, and the brightest quasar yet known at z>5. High-resolution HST imaging reveals a multiple imaged system with a maximum image separation theta ~ 0.2, best explained by a model of three quasar images lensed by a low luminosity galaxy at z~0.7, with a magnification factor of ~50. The existence of this source suggests that a significant population of strongly lensed, high redshift quasars could have been missed by previous surveys, as standard color selection techniques would fail when the quasar color is contaminated by the lensing galaxy.
We present the detection at 89 $mu$m (observed frame) of the {it Herschel}-selected gravitationally lensed starburst galaxy HATLASJ1429-0028 (also known as G15v2.19) in 15 minutes with the High-resolution Airborne Wideband Camera-plus (HAWC+) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). The spectacular lensing system consists of an edge-on foreground disk galaxy at $z$ = 0.22 and a nearly complete Einstein ring of an intrinsic ultra-luminous infrared galaxy at $z$ = 1.03. Is this high IR luminosity powered by pure star formation (SF) or also an active galactic nucleus (AGN)? Previous nebular line diagnostics indicate that it is star-formation dominated. We perform a 27-band multi-wavelength spectral energy distribution modeling (SED) including the new SOFIA/HAWC+ data to constrain the fractional AGN contribution to the total IR luminosity. The AGN fraction in the IR turns out to be negligible. In addition, J1429-0028 serves as a testbed for comparing SED results from different models/templates and SED codes (MAGPHYS, SED3FIT, and CIGALE). We stress that star formation history is the dominant source of uncertainty in the derived stellar mass (as high as a factor of $sim$ 10) even in the case of extensive photometric coverage. Furthermore, the detection of a source at $z$ $sim$ 1 with SOFIA/HAWC+ demonstrates the potential of utilizing this facility for distant galaxy studies including the decomposition of SF/AGN components, which cannot be accomplished with other current facilities.
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