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Register a new userGas reservoir of a hyper-luminous QSO at z=2.6
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Understanding the relationship between the formation and evolution of galaxies and their central super massive black holes (SMBH) is one of the main topics in extragalactic astrophysics. Links and feedback may reciprocally affect both black hole and galaxy growth. Observations of the CO line at redshifts of 2-4 are crucial to investigate the gas mass, star formation activity and accretion onto SMBHs, as well as the effect of AGN feedback. Potential correlations between AGN and host galaxy properties can be highlighted by observing extreme objects. Despite their luminosity, hyper-luminous QSOs at z=2-4 are still little studied at mm wavelengths. We targeted CO(3-2) in ULAS J1539+0557, an hyper-luminos QSO (Lbol> 10^48 erg/s) at z=2.658, selected through its unusual red colors in the UKIDSS Large Area Survey (ULAS). We find a molecular gas mass of 4.1+-0.8 10^10 Msun, and a gas fraction of 0.4-0.1, depending mostly on the assumed source inclination. We also find a robust lower limit to the star-formation rate (SFR=250-1600 Msun/yr) and star-formation efficiency (SFE=25-350 Lsun/(K km s-1 pc2) by comparing the observed optical-near-infrared spectral energy distribution with AGN and galaxy templates. The black hole gas consumption timescale, M(H_2)/dM(accretion)/dt, is ~160 Myr, similar or higher than the gas consumption timescale. The gas content and the star formation efficiency are similar to those of other high-luminosity, highly obscured QSOs, and at the lower end of the star-formation efficiency of unobscured QSOs, in line with predictions from AGN-galaxy co-evolutionary scenarios. Further measurements of the (sub)-mm continuum in this and similar sources are mandatory to obtain a robust observational picture of the AGN evolutionary sequence.
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We present an ALMA high-resolution observation of the 840 um continuum and [CII] line emission in the WISE-SDSS selected hyper-luminous (WISSH) QSO J1015+0020 at z~4.4. Our analysis reveals an exceptional overdensity of [CII]-emitting companions with a very small (<150 km/s) velocity shift with respect to the QSO redshift. We report the discovery of the closest companion observed so far in submillimetre observations of high-z QSOs. It is only 2.2 kpc distant and merging with J1015+0020, while two other [CII] emitters are found at 8 and 17 kpc. Two strong continuum emitters are also detected at <3.5 arcsec. They are likely associated to the same overdense structure of J1015+0020, as they exceed by a factor of 100 the number of expected sources, considering the Log(N)-Log(S) at 850 um. The host galaxy of J1015+0020 shows a SFR of about 100 Msun/yr while the total SFR of the QSO and its companion galaxies is a factor of 10 higher, indicating that substantial stellar mass assembly at early epochs may have taken place in the QSO satellites. For J1015+0020 we compute a SMBH mass MBH~6E9 Msun and a dynamical mass Mdyn~4E10 Msun . This translates into an extreme ratio Mdyn/MBH~7. The total stellar mass of the QSO host galaxy plus the [CII] emitters already exceeds 1E11 Msun at z~4.4. These sources will likely merge and develop into a giant galaxy of 1.3E12 Msun. Under the assumption of constant mass or Eddington accretion rate equal to the observed values, we find that the growth timescale of the host galaxy is comparable or even shorter than that inferred for the SMBH.
We present the correlations between stellar mass, star formation rate (SFR) and [NII]/Ha flux ratio as indicator of gas-phase metallicity for a sample of 222 galaxies at 0.8 < z < 2.6 and log(M*/Msun)=9.0-11.5 from the LUCI, SINS/zC-SINF and KMOS3D surveys. This sample provides a unique analysis of the mass-metallicity relation (MZR) over an extended redshift range using consistent data analysis techniques and strong-line metallicity indicator. We find a constant slope at the low-mass end of the relation and can fully describe its redshift evolution through the evolution of the characteristic turnover mass where the relation begins to flatten at the asymptotic metallicity. At fixed mass and redshift, our data do not show a correlation between the [NII]/Ha ratio and SFR, which disagrees with the 0.2-0.3dex offset in [NII]/Ha predicted by the fundamental relation between stellar mass, SFR and metallicity discussed in recent literature. However, the overall evolution towards lower [NII]/Ha at earlier times does broadly agree with these predictions.
We investigate the role of the environment in processing molecular gas in radio galaxies (RGs). We observed five RGs at $z=0.4-2.6$ in dense Mpc-scale environment with the IRAM-30m telescope. We set four upper-limits and report a tentative CO(7$rightarrow$6) detection for COSMOS-FRI 70 at $z=2.63$, which is the most distant brightest cluster galaxy (BCG) candidate detected in CO. We speculate that the cluster environment might have played a role in preventing the refueling via environmental mechanisms such as galaxy harassment, strangulation, ram-pressure, or tidal stripping. The RGs of this work are excellent targets for ALMA as well as next generation telescopes such as the James Webb Space Telescope.
We investigate the role of dense Mpc-scale environment in processing molecular gas in distant Low luminosity radio galaxies (LLRGs) in galaxy (proto-)clusters. We have selected within the COSMOS and DES surveys a sample of five LLRGs at $z=0.4-2.6$ that show evidence of ongoing star formation on the basis of their far-infrared emission. We have assembled and modeled the far-infrared-to-ultraviolet spectral energy distributions (SEDs) of the LLRGs. We have observed the sources with the IRAM-30m telescope to search for CO emission. We have then searched for dense Mpc-scale overdensities associated with the LLRGs using photometric redshifts of galaxies and the Poisson Probability Method, that we have upgraded using the wavelet-transform ($mathit{w}$PPM), to characterize the overdensity in the projected space. Color-color and color-magnitude plots have been derived for the fiducial cluster members. We set upper limits to the CO emission of the LLRGs, at $z=0.39, 0.61, 0.91, 0.97$, and $2.6$. For the most distant radio source, COSMOS-FRI 70 at $z=2.6$, a hint of CO(7$rightarrow$6) emission is found at 2.2$sigma$. The upper limits found for the molecular gas content $M({rm H}_2)/M_star<0.11$, 0.09, 1.8, 1.5, and 0.29, respectively, and depletion time $tau_{rm dep}lesssim(0.2-7)$ Gyr of the five LLRGs are overall consistent with the values of main sequence field galaxies. Our SED modeling implies large stellar masses for the LLRGs, in the range $log(M_star/M_odot)=10.9-11.5$, while the associated Mpc-scale overdensities show a complex morphology. The color-color and color-magnitude plots suggest that the LLRGs are consistent with being star forming and on the high-luminosity tail of the red sequence. The present study increases the limited statistics of distant cluster core galaxies with CO observations. The radio galaxies of this work are excellent targets for ALMA and JWST.
We present a multiwavelength study of the AGN-host starburst galaxy PKS 0529-549 at z~2.6. We use (1) new ALMA observations of the dust continuum and of the [CI] 370 um line, tracing molecular gas, (2) SINFONI spectroscopy of the [OIII] 5007 Ang line, tracing ionized gas, and (3) ATCA radio continuum images, tracing synchrotron emission. Both [CI] and [OIII] show regular velocity gradients, but their systemic velocities and position angles differ by ~300 km/s and ~30 degrees, respectively. The [CI] is consistent with a rotating disc, aligned with the dust and stellar continuum, while the [OIII] likely traces an outflow, aligned with two AGN-driven radio lobes. We model the [CI] cube using 3D disc models, which give best-fit rotation velocities V~310 km/s and velocity dispersions sigma<30 km/s. Hence, the [CI] disc has V/sigma>10 and is not particularly turbulent, similar to local galaxy discs. The dynamical mass (~10^11 Msun) is comparable to the baryonic mass within the errors. This suggests that baryons dominate the inner galaxy dynamics, similar to massive galaxies at z=0. Remarkably, PKS 0529-549 lies on the local baryonic Tully-Fisher relation, indicating that at least some massive galaxies are already in place and kinematically relaxed at z~2.6. This work highlights the potential of the [CI] line to trace galaxy dynamics at high z, as well as the importance of multiwavelength data to interpret gas kinematics.
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