We present high-resolution (\(\lesssim0.1\)arcsec) ALMA observations of the strongly-lensed galaxy HATLASJ113526.2-01460 at redshift \(z\sim3.1\) discovered in the Gama 12\(^{\rm th}\) field of the ...Herschel-ATLAS survey. The gravitationally lensed system is remarkably peculiar in that neither the background source nor the foreground lens show a clearly detected optical/NIR emission. We perform accurate lens modeling and source morphology reconstruction in three different (sub-)mm continuum bands, and in the CII and CO(8-7) spectral lines. The modeling indicates a foreground lensing (likely elliptical) galaxy with mass \(\gtrsim10^{11}\, M_\odot\) at \(z\gtrsim1.5\), while the source (sub-)mm continuum and line emissions are amplified by factors \(\mu\sim6-13\). We estimate extremely compact sizes \(\lesssim0.5\) kpc for the star-forming region and \(\lesssim 1\) kpc for the gas component, with no clear evidence of rotation or of ongoing merging events. We perform broadband SED-fitting and retrieve the intrinsic de-magnified physical properties of the source, which is found to feature a very high star-formation rate \(\gtrsim10^3\, M_\odot\) yr\(^{-1}\), that given the compact sizes is on the verge of the Eddington limit for starbursts; the radio luminosity at 6 cm from available EVLA observations is consistent with the star-formation activity. The galaxy is found to be extremely rich in gas \(\sim10^{11}\, M_\odot\) and dust \(\gtrsim10^9\, M_\odot\). The stellar content \(\lesssim10^{11}\, M_\odot\) places the source well above the main sequence of starforming galaxies, indicating that the starburst is rather young with estimated age \(\sim10^8\) yr. Our results indicate that the overall properties of HATLASJ113526.2-01460 are consistently explained by in-situ galaxy formation and evolution scenarios.
We report ALMA high-resolution observations of water emission lines
$p-{\rm{H_2O}} (2_{02}-1_{11}$), $o-{\rm{H_2O}} (3_{21}-3_{12})$,
$p-{\rm{H_2O}} (4_{22}-4_{13})$, in the strongly lensed galaxy
...HATLASJ113526.2-01460 at redshift z $\sim$ 3.1. From the lensing-reconstructed
maps of water emission and line profiles, we infer the general physical
properties of the ISM in the molecular clouds where the lines arise. We find
that the water vapor lines $o-{\rm{H_2O}} (3_{21}-3_{12})$, $p-{\rm{H_2O}}
(4_{22}-4_{13})$ are mainly excited by FIR pumping from dust radiation in a
warm and dense environment, with dust temperatures ranging from 70 K to $\sim
100$ K, as suggested by the line ratios. The $p-{\rm{H_2O}} (2_{02}-1_{11})$
line instead, is excited by a complex interplay between FIR pumping and
collisional excitation in the dense core of the star-forming region. This
scenario is also supported by the detection of the medium-level excitation of
CO resulting in the line emission CO (J=8-7). Thanks to the unprecedented high
resolution offered by the combination of ALMA capabilities and gravitational
lensing, we discern the different phases of the ISM and locate the hot
molecular clouds into a physical scale of $\sim$ 500 pc. We discuss the
possibility of J1135 hosting an AGN in its accretion phase. Finally, we
determine the relation between the water emission lines and the total IR
luminosity of J1135, as well as the SFR as a function of water emission
intensities, comparing the outcomes to local and high-$z$ galactic samples from
the literature.
We present HOMERUN (Highly Optimized Multi-cloud Emission-line Ratios Using photo-ionizatioN), a new approach to modelling emission lines from photoionized gas that can simultaneously reproduce all ...observed line intensities from a wide range of ionization levels and with high accuracy. Our approach is based on the weighted combination of multiple single-cloud photoionization models and, contrary to previous works, the novelty of our approach consists in using the weights as free parameters of the fit and constraining them with the observed data. One of the main applications of HOMERUN is the accurate determination of gas-phase metallicities and we show that a critical point is to allow for a variation of the N/O and S/O abundance ratios which can significantly improve the quality of the fit and the accuracy of the results. Moreover, our approach provides a major improvement compared to the single-cloud, constant-pressure models commonly used in the literature. By using high-quality literature spectra of H ii regions where 10 to 20 emission lines (including several auroral lines) are detected with high signal-to-noise ratio, we show that all lines are reproduced by the model with an accuracy better than 10%. In particular, the model is able to simultaneously reproduce O i6300, 6363, O ii3726, 3729, O iii4959, 5007, S ii6717, 6731, and S iii9069, 9532 emission lines which, to our knowledge, is an unprecedented result. Finally, we show that the gas metallicities estimated with our models for HII regions in the Milky Way are in agreement with the stellar metallicities than the estimates based on the Te-method. Overall, our method provides a new accurate tool to estimate the metallicity and the physical conditions of the ionized gas. It can be applied to many different science cases from HII regions to AGN and wherever there are emission lines from photoionized gas.
We present Atacama Large Millimeter/submillimeter Array (ALMA) Band 5
observations of a galaxy at $z=1.91$, GDS24569, in search of molecular gas in
its vicinity via the C I $^3$P$_1$-$^3$P$_0$ line. ...GDS24569 is a massive
($\log M_*/M_\odot=11$) passively evolving galaxy, and characterized by compact
morphology with an effective radius of $\sim0.5$ kpc. We apply two blind
detection algorithms to the spectral data cubes, and find no promising
detection in or around GDS24569 out to projected distance of $\sim320$ kpc,
while a narrow tentative line ($4.1 \sigma$) is identified at $+1200$ km/s by
one of the algorithms. From the non-detection of C I, we place a $3\sigma$
upper limit on molecular hydrogen mass, $\sim 7.1 \times 10^9 M_\odot$, which
converts to an extremely low gas-to-stellar mass fraction, $< 5 \%$. We conduct
a spectral energy distribution modeling by including optical-to-far-infrared
data, and find a considerably high ($\sim0.1\%$) dust-to-stellar mass ratio,
$\sim10$-$100\times$ higher than those of local early-type galaxies. In
combination with a previous result of an insufficient number of surrounding
satellite galaxies, it is suggested that GDS24569 is unlikely to experience
significant size evolution via satellite mergers. We discuss possible physical
mechanisms that quenched GDS24569.
We investigate the radio-far infrared (FIR) correlation for a sample of \(28\) bright high-redshift (\(1 \lesssim z \lesssim 4\)) star-forming galaxies selected in the FIR from the Herschel-ATLAS ...fields as candidates to be strongly gravitationally lensed. The radio information comes either from high sensitivity dedicated ATCA observations at \(2.1\) GHz or from cross-matches with the FIRST survey at \(1.4\) GHz. By taking advantage of source brightness possibly enhanced by lensing magnification, we identify a weak evolution with redshift out to \(z\lesssim 4\) of the FIR-to-radio luminosity ratio \(q_{\rm FIR}\). We also find that the \(q_{\rm FIR}\) parameter as a function of the radio power \(L_{1.4\,\rm GHz}\) displays a clear decreasing trend, similarly to what is observed for optically/radio selected lensed quasars found in literature, yet covering a complementary region in the \(q_{\rm FIR}-L_{1.4\,\rm GHz}\) diagram. We interpret such a behavior in the framework of an in-situ galaxy formation scenario, as a result of the transition from an early dust-obscured star-forming phase (mainly pinpointed by our FIR selection) to a late radio-loud quasar phase (preferentially sampled by the optical/radio selection).
In this work we performed a spectral energy distribution (SED) analysis in the optical/infrared band of the host galaxy of a proto-brightest cluster galaxy (BCG, NVSS J103023+052426) in a ...proto-cluster at z = 1.7. We found that it features a vigorous star formation rate (SFR) of \({\sim}\)570 \(\mathrm{M_{\odot}}\)/yr and a stellar mass of \(M_{\ast} \sim 3.7 \times 10^{11}\) \(\mathrm{M_{\odot}}\); the high corresponding specific SFR = \(1.5 \pm 0.5\) \(\mathrm{Gyr^{-1}}\) classifies this object as a starburst galaxy that will deplete its molecular gas reservoir in \(\sim\) \(3.5 \times 10^8\) yr. Thus, this system represents a rare example of a proto-BCG caught during the short phase of its major stellar mass assembly. Moreover, we investigated the nature of the host galaxy emission at 3.3 mm. We found that it originates from the cold dust in the interstellar medium, even though a minor non-thermal AGN contribution cannot be completely ruled out. Finally, we studied the polarized emission of the lobes at 1.4 GHz. We unveiled a patchy structure where the polarization fraction increases in the regions in which the total intensity shows a bending morphology; in addition, the magnetic field orientation follows the direction of the bendings. We interpret these features as possible indications of an interaction with the intracluster medium. This strengthens the hypothesis of positive AGN feedback, as inferred in previous studies of this object on the basis of X-ray/mm/radio analysis. In this scenario, the proto-BCG heats the surrounding medium and possibly enhances the SFR in nearby galaxies.
We present deep L-Band observations of the equatorial field centered on the z=6.3 SDSS QSO, reaching a 1 sigma sensitivity of ~2.5 uJy at the center of the field. We extracted a catalog of 1489 radio ...sources down to a flux density of ~12.5 uJy (5 sigma) over a field of view of ~ 30' diameter. We derived the source counts accounting for catalog reliability and completeness, and compared them with others available in the literature. Our source counts are among the deepest available so far, and, overall, are consistent with recent counts' determinations and models. We detected for the first time in the radio band the SDSS J1030+0524 QSO (26 +/- 5 uJy). We derived its optical radio loudness R_O = 0.62 +/- 0.12, which makes it the most radio quiet AGN at z >~ 6 discovered so far and detected at radio wavelengths. We unveiled extended diffuse radio emission associated with the lobes of a bright FRII radio galaxy located close to the center of the J1030 field, which is likely to become the future BCG of a protocluster at z=1.7. The lobes' complex morphology, coupled with the presence of X-ray diffuse emission detected around the FRII galaxy lobes, may point toward an interaction between the radio jets and the external medium. We also investigated the relation between radio and X-ray luminosity for a sample of 243 X-ray-selected objects obtained from 500 ks Chandra observations of the same field, and spanning a wide redshift range (0 ~< z ~< 3). Focused on sources with a spectroscopic redshift and classification, we found that sources hosted by ETG and AGN follow Log(L_R)/Log(L_X) linear correlations with slopes of ~0.6 and ~0.8, respectively. This is interpreted as a likely signature of different efficiency in the accretion process. Finally, we found that most of these sources (>~87%) show a radio-to-X-ray radio loudness R_X < -3.5, classifying these objects as radio quiet.
Measurements of the size of dust continuum emission are an important tool for constraining the spatial extent of star formation and hence the build-up of stellar mass. Compact dust emission has ...generally been observed at Cosmic Noon (z~2-3). However, at earlier epochs, toward the end of the Reionization (z~4-6), only the sizes of a handful of IR-bright galaxies have been measured. In this work, we derive the dust emission sizes of main-sequence galaxies at z~5 from the ALPINE survey. We measure the dust effective radius r_e,FIR in the uv-plane in Band 7 of ALMA for seven ALPINE galaxies with resolved emission and we compare it with rest-frame UV and CII158\(\mu\)m measurements. We study the r_e,FIR-L_IR scaling relation by considering our dust size measurements and all the data in literature at z~4-6. Finally, we compare our size measurements with predictions from simulations. The dust emission in the selected ALPINE galaxies is rather extended (r_e,FIR~1.5-3 kpc), similar to CII158 um but a factor of ~2 larger than the rest-frame UV emission. Putting together all the measurements at z~5, spanning 2 decades in luminosity from L_IR ~ 10^11 L_sun to L_IR ~ 10^13 L_sun, the data highlight a steeply increasing trend of the r_e,FIR-L_IR relation at L_IR< 10^12 L_sun, followed by a downturn and a decreasing trend at brighter luminosities. Finally, simulations that extend up to the stellar masses of the ALPINE galaxies considered in the present work predict a sub-set of galaxies (~25% at 10^10 M_sun < M_star < 10^11 M_sun) with sizes as large as those measured.
We combine results from deep ALMA observations of massive (\(M_*>10^{10}\;M_{\odot}\)) galaxies at different redshifts to show that the column density of their inter stellar medium (ISM) rapidly ...increases towards early cosmic epochs. Our analysis includes objects from the ASPECS and ALPINE large programs, as well as individual observations of \(z\sim 6\) QSO hosts. When accounting for non-detections and correcting for selection effects, we find that the median surface density of the ISM of the massive galaxy population evolves as \(\sim(1+z)^{3.3}\). This means that the ISM column density towards the nucleus of a \(z>3\) galaxy is typically \(>100\) times larger than locally, and it may reach values as high as Compton-thick at \(z\gtrsim6\). Remarkably, the median ISM column density is of the same order of what is measured from X-ray observations of large AGN samples already at \(z\gtrsim2\). We develop a simple analytic model for the spatial distribution of ISM clouds within galaxies, and estimate the total covering factor towards active nuclei when obscuration by ISM clouds on the host scale is added to that of pc-scale circumnuclear material (the so-called 'torus'). The model includes clouds with a distribution of sizes, masses, and surface densities, and also allows for an evolution of the characteristic cloud surface density with redshift, \(\Sigma_{c,*}\propto(1+z)^\gamma\). We show that, for \(\gamma=2\), such a model successfully reproduces the increase of the obscured AGN fraction with redshift that is commonly observed in deep X-ray surveys, both when different absorption thresholds and AGN luminosities are considered. Our results suggest that 80-90\% of supermassive black holes in the early Universe (\(z>6-8\)) are hidden to our view, primarily by the ISM in their hosts. abridged
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