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Register a new userMultiwavelength characterisation of an ACT-selected, lensed dusty star-forming galaxy at z=2.64
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Guido Roberts-Borsani
Publication date
2017
fields
Physics
and research's language is
English
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We present ci,(2--1) and multi-transition $^{12}$CO observations of a dusty star-forming galaxy, ACT,J2029+0120, which we spectroscopically confirm to lie at $z$,=,2.64. We detect CO(3--2), CO(5--4), CO(7--6), CO(8--7), and ci,(2--1) at high significance, tentatively detect HCO$^{+}$(4--3), and place strong upper limits on the integrated strength of dense gas tracers (HCN(4--3) and CS(7--6)). Multi-transition CO observations and dense gas tracers can provide valuable constraints on the molecular gas content and excitation conditions in high-redshift galaxies. We therefore use this unique data set to construct a CO spectral line energy distribution (SLED) of the source, which is most consistent with that of a ULIRG/Seyfert or QSO host object in the taxonomy of the textit{Herschel} Comprehensive ULIRG Emission Survey. We employ RADEX models to fit the peak of the CO SLED, inferring a temperature of T$sim$117 K and $n_{text{H}_2}sim10^5$ cm$^{-3}$, most consistent with a ULIRG/QSO object and the presence of high density tracers. We also find that the velocity width of the ci line is potentially larger than seen in all CO transitions for this object, and that the $L_{rm C,I(2-1)}/L_{rm CO(3-2)}$ ratio is also larger than seen in other lensed and unlensed submillimeter galaxies and QSO hosts; if confirmed, this anomaly could be an effect of differential lensing of a shocked molecular outflow.
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We report the detection of a massive neutral gas outflow in the z=2.09 gravitationally lensed Dusty Star-Forming Galaxy HATLASJ085358.9+015537 (G09v1.40), seen in absorption with the OH+(1_1-1_0) transition using spatially resolved (0.5x0.4) Atacama Large Millimeter/submillimeter Array (ALMA) observations. The blueshifted OH+ line is observed simultaneously with the CO(9-8) emission line and underlying dust continuum. These data are complemented by high angular resolution (0.17x0.13) ALMA observations of CH+(1-0) and underlying dust continuum, and Keck 2.2 micron imaging tracing the stellar emission. The neutral outflow, dust, dense molecular gas and stars all show spatial offsets from each other. The total atomic gas mass of the observed outflow is 6.7x10^9 M_sun, >25% as massive as the gas mass of the galaxy. We find that a conical outflow geometry best describes the OH+ kinematics and morphology and derive deprojected outflow properties as functions of possible inclination (0.38 deg-64 deg). The neutral gas mass outflow rate is between 83-25400 M_sun/yr, exceeding the star formation rate (788+/-300 M_sun/yr) if the inclination is >3.6 deg (mass-loading factor = 0.3-4.7). Kinetic energy and momentum fluxes span 4.4-290x10^9 L_sun and 0.1-3.7x10^37 dyne, respectively (energy-loading factor = 0.013-16), indicating that the feedback mechanisms required to drive the outflow depend on the inclination assumed. We derive a gas depletion time between 29 and 1 Myr, but find that the neutral outflow is likely to remain bound to the galaxy, unless the inclination is small, and may be re-accreted if additional feedback processes do not occur.
We present a physical characterization of MMJ100026.36+021527.9 (a.k.a. ``MAMBO-9), a dusty star-forming galaxy (DSFG) at $z=5.850pm0.001$. This is the highest redshift unlensed DSFG (and fourth most distant overall) found to-date, and is the first source identified in a new 2mm blank-field map in the COSMOS field. Though identified in prior samples of DSFGs at 850$mu$m-1.2mm with unknown redshift, the detection at 2mm prompted further follow-up as it indicated a much higher probability that the source was likely to sit at $z>4$. Deep observations from the Atacama Large Millimeter and submillimeter Array (ALMA) presented here confirm the redshift through the secure detection of $^{12}$CO($J!=$6$rightarrow$5) and p-H$_{2}$O(2$_{1,1}!rightarrow$2$_{0,2}$). MAMBO-9 is comprised of a pair of galaxies separated by 6kpc with corresponding star-formation rates of 590M$_odot$yr$^{-1}$ and 220M$_odot$yr$^{-1}$ total molecular hydrogen gas mass of (1.7$pm$0.4)$times10^{11}$M$_odot$, dust mass of (1.3$pm$0.3)$times10^{9}$M$_odot$ and stellar mass of (3.2$^{+1.0}_{-1.5}$)$times10^{9}$M$_odot$. The total halo mass, (3.3$pm$0.8)$times10^{12}$M$_odot$, is predicted to exceed $>10^{15}$M$_odot$ by $z=0$. The system is undergoing a merger-driven starburst which will increase the stellar mass of the system tenfold in $tau_{rm depl}=40-80$Myr, converting its large molecular gas reservoir (gas fraction of 96$^{+1}_{-2}$%) into stars. MAMBO-9 evaded firm spectroscopic identification for a decade, following a pattern that has emerged for some of the highest redshift DSFGs found. And yet, the systematic identification of unlensed DSFGs like MAMBO-9 is key to measuring the global contribution of obscured star-formation to the star-formation rate density at $z>4$, the formation of the first massive galaxies, and the formation of interstellar dust at early times ($<$1Gyr).
We present the serendipitous ALMA detection of a faint submillimeter galaxy (SMG) lensed by a foreground z~1 galaxy. By optimizing the source detection to deblend the system, we accurately build the full spectral energy distribution of the distant galaxy from the I814 band to radio wavelengths. It is extremely red, with a I-K colour larger than 2.5. We estimate a photometric redshift of 3.28 and determine the physical parameters. The distant galaxy turns out to be magnified by the foreground lens by a factor of ~1.5, which implies an intrinsic Ks-band magnitude of ~24.5, a submillimeter flux at 870um of ~2.5 mJy and a SFR of ~150-300Msun/yr, depending on the adopted tracer. These values place our source towards the faint end of the distribution of observed SMGs, and in particular among the still few faint SMGs with a fully characterized spectral energy distribution, which allows us not only to accurately estimate its redshift but also to measure its stellar mass and other physical properties. The galaxy studied in this work is a representative of the population of faint SMGs, of which only few objects are known to date, that are undetected in optical and therefore are not typically accounted for when measuring the cosmic star formation history (SFH). This faint galaxy population thus likely represents an important and missing piece in our understanding of the cosmic SFH. Its observation and characterization is of major importance to achieve a solid picture of galaxy evolution.
We report Northern Extended Millimeter Array (NOEMA) CO($J = 3 - 2$) observations of the dusty star-forming galaxy ACT-S,J020941+001557 at $z = 2.5528$, which was detected as an unresolved source in the Atacama Cosmology Telescope (ACT) equatorial survey. Our spatially resolved spectral line data support the derivation of a gravitational lens model from 37 independent velocity channel maps using a pixel-based algorithm, from which we infer a velocity-dependent magnification factor $mu approx 7-22$ with a luminosity-weighted mean $left<muright>approx 13$. The resulting source-plane reconstruction is consistent with a rotating disk, although other scenarios cannot be ruled out by our data. After correction for lensing, we derive a line luminosity $L^{prime}_{rm CO(3-2)}= (5.53pm 0.69) times 10^{10},{rm ,K,km,s^{-1},pc^{2}}$, a cold gas mass $M_{{rm gas}}= (3.86 pm 0.33) times 10^{10},M_{odot}$, a dynamical mass $M_{rm dyn},{rm sin}^2,i = 3.9^{+1.8}_{-1.5} times 10^{10},M_{odot}$, and a gas mass fraction $f_{rm gas},{rm csc}^2,i = 1.0^{+0.8}_{-0.4}$. The line brightness temperature ratio of $r_{3,1}approx 1.6$ relative to a Green Bank Telescope CO($J=1-0$) detection may be elevated by a combination of external heating of molecular clouds, differential lensing, and/or pointing errors.
We report the discovery of a molecular wind signature from a massive intensely star-forming clump of a few $10^9$ Msun, in the strongly gravitationally lensed submillimeter galaxy the Emerald (PLCK_G165.7+49.0) at z=2.236. The Emerald is amongst the brightest high-redshift galaxies on the submillimeter sky, and was initially discovered with the Planck satellite. The system contains two magnificient structures with projected lengths of 28.5 and 21 formed by multiple, near-infrared arcs, falling behind a massive galaxy cluster at z=0.35, as well as an adjacent filament that has so far escaped discovery in other wavebands. We used HST/WFC3 and CFHT optical and near-infrared imaging together with IRAM and SMA interferometry of the CO(4-3) line and 850 $mu$m dust emission to characterize the foreground lensing mass distribution, construct a lens model with Lenstool, and calculate gravitational magnification factors between 20 and 50 in most of the source. The majority of the star formation takes place within two massive star-forming clumps which are marginally gravitationally bound and embedded in a $9 times 10^{10}$ Msun, fragmented disk with 20% gas fraction. One of the clumps shows a pronounced blue wing in the CO(4-3) line profile, which we interpret as a wind signature. The mass outflow rates are high enough for us to suspect that the clump might become unbound within a few tens of Myr, unless the outflowing gas can be replenished by gas accretion from the surrounding disk. The velocity offset of -200 km s$^{-1}$ is above the escape velocity of the clump, but not that of the galaxy overall, suggesting that much of this material might ultimately rain back onto the galaxy and contribute to fueling subsequent star formation.
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