arXiv subjects

J. Freundlich

Publications and source records attributed to J. Freundlich.

At least 19 recordsLinked to original sources

arXiv2026

MUSE-DARK III: The evolution of the radial acceleration relation at intermediate redshifts

The radial acceleration relation (RAR) is a tight empirical correlation between the observed radial acceleration (a_tot) and the baryonic radial acceleration (a_bar) measured across galaxy radii: these two accelerations start to deviate significantly from each other below a characteristic acceleration scale, a0. So far, observational studies of the RAR have predominantly focused on galaxies in the local Universe, leaving its evolution with cosmic time largely unexplored. Using high signal-to-noise data from the MUSE Hubble Ultra Deep Field survey, we investigate the RAR with a sample of 79 star-forming galaxies (complete above M* >10^8.8 Msun) at intermediate redshifts (0.33 <z <1.44). We estimate the observed intrinsic acceleration and the baryonic acceleration from a disk-halo decomposition that incorporates stellar, gas, and dark matter components, with corrections for pressure support, using 3D forward modelling. We find a RAR in our intermediate-z sample offset from the local relation, with a higher characteristic acceleration scale, a0(z~1) = 2.38+/-0.1* 10^-10 m/s^2, and a larger intrinsic scatter (~0.17 dex). Dividing the sample into redshift bins and refitting the RAR in each bin, we find a characteristic acceleration scale that systematically increases with z. Parametrizing the z-dependence as a0(z)= a0(0) + a1 * z, we obtain a1 = 1.59+/-0.1 *10^-10 m/s^2, providing evidence for a z-evolution. We find similar results using various dark matter halo profiles as well as the Modified Newtonian Dynamics framework in our 3D forward modelling. Our results show that the RAR persists at intermediate redshift, with statistically significant redshift evolution of the characteristic acceleration, pointing to a possible evolution of the baryon-missing mass connection over cosmic time.

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arXiv2026

Evaluating star formation rates at z = 5

Inferring the star formation rates (SFR) in high redshift galaxies remains challenging, owing to observational limitations or uncertainties in calibration methods that link luminosities to SFRs. We utilize two state-of-the-art hydrodynamical simulations NewHorizon and NewCluster, post-processed with the radiative transfer code Skirt, to investigate the systematic uncertainties and biases in the inferred SFRs for z=5 galaxies; an epoch where galaxies build-up their stellar mass. We create synthetic observables for widely-used tracers: Halpha nebular line, [CII] 158 micron fine-structure line, total infrared (IR) continuum luminosity, and hybrid (IR + UV). We find that Halpha-inferred SFRs, time-averaged over 10 Myr, are sensitive to the choice of calibration and exhibit substantial scatter driven by dust attenuation, viewing angle, and dust-to-metal ratio. Adopting a steeper attenuation curve reduces this scatter significantly but does not fully eliminate systematic uncertainties. IR continuum-based SFRs trace intrinsic SFRs time-averaged over 100 Myr timescales when a well-sampled continuum emission between restframe 8 and 1000 micron is available and underestimate them with typical approaches when IR data are limited. Nevertheless, IR SFRs display a considerable scatter, largely due to UV photon leakage and strong variations in the star formation history. When UV data are available, hybrid (IR + UV) SFRs provide a more robust estimate, reducing scatter compared to IR-based SFRs while avoiding explicit attenuation corrections. Finally, we derive a [CII]-SFR relation finding a steeper relation than previous studies, however with significant scatter linked to gas density and metallicity. Overall, IR-, hybrid-, and [CII]-based tracers remain more robust than Halpha against variations in optical depth.

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arXiv2025

YOLO-CIANNA: Galaxy detection with deep learning in radio data: II. Winning the SKA SDC2 using a generalized 3D-YOLO network

As the scientific exploitation of the Square Kilometre Array (SKA) approaches, there is a need for new advanced data analysis and visualization tools capable of processing large high-dimensional datasets. In this study, we aim to generalize the YOLO-CIANNA deep learning source detection and characterization method for 3D hyperspectral HI emission cubes. We present the adaptations we made to the regression-based detection formalism and the construction of an end-to-end 3D convolutional neural network (CNN) backbone. We then describe a processing pipeline for applying the method to simulated 3D HI cubes from the SKA Observatory Science Data Challenge 2 (SDC2) dataset. The YOLO-CIANNA method was originally developed and used by the MINERVA team that won the official SDC2 competition. Despite the public release of the full SDC2 dataset, no published result has yet surpassed MINERVA's top score. In this paper, we present an updated version of our method that improves our challenge score by 9.5%. The resulting catalog exhibits a high detection purity of 92.3%, best-in-class characterization accuracy, and contains 45% more confirmed sources than concurrent classical detection tools. The method is also computationally efficient, processing the full ~1TB SDC2 data cube in 30 min on a single GPU. These state-of-the-art results highlight the effectiveness of 3D CNN-based detectors for processing large hyperspectral data cubes and represent a promising step toward applying YOLO-CIANNA to observational data from SKA and its precursors.

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arXiv2025

Dynamical traction and black hole orbital migration

We investigate the circumstances which allow a black hole to remain put at the galactic centre when the stellar core is anisotropic. We use N-body calculations to study the response of stellar orbit families embedded in a larger, isotropic isochrone (H\'enon) background potential. When the BH orbits in an odd f[E,Lz] velocity distribution function, they transfer angular momentum to it. We call this dynamical traction: it takes place whenever the kinetic energy drawn from f[E,Lz] has an excess of streaming motion over its (isotropic) v-dispersion. For a dynamically cold disc, the outcome depends on both the orbit of the BH and that of a Jeans-unstable stellar sub-structures. When the stellar clumps have much binding energy, a BH may scatter off of them after they formed. In the process the BH may be dislodged from the centre and migrate outward due to dynamical traction. When the stellar clumps are less bound, they may still migrate to the centre where they either dissolve or merge with the BH. The final configuration is similar to a nuclear star cluster which may yet be moving at ~10 km/s wrt the barycentre. The angular momentum transferred to a BH by dynamical traction delays the migration to the galactic centre by several hundred million years. The efficiency of angular momentum transfer is a strong function of the fragmented (cold) state of the stellar space density. In a dynamically cold environment, a BH is removed from the central region through a two-stage orbital migration instability. A criterion against this instability is proposed in the form of a threshold in isotropic velocity dispersion compared to streaming motion. For a BH to settle at the heart of a galaxy on time-scales of ~ 300 Myr or less requires that a large fraction of Lz be dissipated, or, alternatively, that the BH grows in situ in an isotropic environment devoid of sub-structures.

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arXiv2024

Predicting HCN, HCO$^+$, multi-transition CO, and dust emission of star-forming galaxies -- Extension to luminous infrared galaxies and the role of cosmic ray ionization

The specific star-formation rate of star-forming `main sequence' galaxies significantly decreased since z~1.5, due to the decreasing molecular gas fraction and star formation efficiency. However, the radio-infrared (IR) correlation has not changed significantly since z~1.5. The theory of turbulent clumpy starforming gas disks together with the scaling relations of the interstellar medium describes the large and small-scale properties of galactic gas disks. Here we extend our previous work on infrared, multi-transition molecular line, and radio continuum emission of local and high-z starforming and starburst galaxies to local and z~0.5 luminous infrared galaxies. The model reproduces the IR luminosities, CO, HCN, and HCO+ line luminosities, and the CO spectral line energy distributions of these galaxies. We derive CO(1-0) and HCN(1-0) conversion factors for all galaxy samples. The relation between the star formation rate per unit area and H2 surface density cannot be fit simply for all redshifts. There is a tight correlation between the star formation efficiency and the product of the gas turbulent velocity dispersion and the angular velocity of the galaxies. Galaxies of lower stellar masses can in principle compensate their gas consumption via star formation by radial viscous gas accretion. The limiting stellar mass increases with redshift. Whereas the radio continuum emission is directly proportional to the density of cosmic ray (CR) electrons, the molecular line emission depends on the CR ionization rate via the gas chemistry. The normalization of the CR ionization rate found for the different galaxy samples is about a factor of three to five higher than the normalization for the Solar neighborhood. This means that the mean yield of low energy CR particles for a given star formation rate per unit area is about three to ten times higher in external galaxies than observed by Voyager I.

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arXiv2024

YOLO-CIANNA: Galaxy detection with deep learning in radio data. I. A new YOLO-inspired source detection method applied to the SKAO SDC1

The upcoming Square Kilometer Array (SKA) will set a new standard regarding data volume generated by an astronomical instrument, which is likely to challenge widely adopted data-analysis tools that scale inadequately with the data size. The aim of this study is to develop a new source detection and characterization method for massive radio astronomical datasets based on modern deep-learning object detection techniques. For this, we seek to identify the specific strengths and weaknesses of this type of approach when applied to astronomical data. We introduce YOLO-CIANNA, a highly customized deep-learning object detector designed specifically for astronomical datasets. In this paper, we present the method and describe all the elements introduced to address the specific challenges of radio astronomical images. We then demonstrate the capabilities of this method by applying it to simulated 2D continuum images from the SKA observatory Science Data Challenge 1 (SDC1) dataset. Using the SDC1 metric, we improve the challenge-winning score by +139% and the score of the only other post-challenge participation by +61%. Our catalog has a detection purity of 94% while detecting 40 to 60% more sources than previous top-score results, and exhibits strong characterization accuracy. The trained model can also be forced to reach 99% purity in post-process and still detect 10 to 30% more sources than the other top-score methods. It is also computationally efficient, with a peak prediction speed of 500 images of 512x512 pixels per second on a single GPU. YOLO-CIANNA achieves state-of-the-art detection and characterization results on the simulated SDC1 dataset and is expected to transfer well to observational data from SKA precursors.

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arXiv2023

The ALMA-ALPINE [CII] survey: Kennicutt-Schmidt relation in four massive main-sequence galaxies at z~4.5

The Kennicutt-Schmidt (KS) relation between the gas and the star formation rate (SFR) surface density ($\Sigma_{\rm gas}$-$\Sigma_{\rm SFR}$) is essential to understand star formation processes in galaxies. So far, it has been measured up to z~2.5 in main-sequence galaxies. In this letter, we aim to put constraints at z~4.5 using a sample of four massive main-sequence galaxies observed by ALMA at high resolution. We obtained ~0.3"-resolution [CII] and continuum maps of our objects, which we then converted into gas and obscured SFR surface density maps. In addition, we produced unobscured SFR surface density maps by convolving Hubble ancillary data in the rest-frame UV. We then derived the average $\Sigma_{\rm SFR}$ in various $\Sigma_{\rm gas}$ bins, and estimated the uncertainties using a Monte Carlo sampling. Our galaxy sample follows the KS relation measured in main-sequence galaxies at lower redshift and is slightly lower than predictions from simulations. Our data points probe the high end both in terms of $\Sigma_{\rm gas}$ and $\Sigma_{\rm gas}$, and gas depletion timescales (285-843 Myr) remain similar to z~2 objects. However, three of our objects are clearly morphologically disturbed, and we could have expected shorter gas depletion timescales (~100 Myr) similar to merger-driven starbursts at lower redshifts. This suggests that the mechanisms triggering starbursts at high redshift may be different than in the low- and intermediate-z Universe.

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arXiv2023

SKA Science Data Challenge 2: analysis and results

The Square Kilometre Array Observatory (SKAO) will explore the radio sky to new depths in order to conduct transformational science. SKAO data products made available to astronomers will be correspondingly large and complex, requiring the application of advanced analysis techniques to extract key science findings. To this end, SKAO is conducting a series of Science Data Challenges, each designed to familiarise the scientific community with SKAO data and to drive the development of new analysis techniques. We present the results from Science Data Challenge 2 (SDC2), which invited participants to find and characterise 233245 neutral hydrogen (Hi) sources in a simulated data product representing a 2000~h SKA MID spectral line observation from redshifts 0.25 to 0.5. Through the generous support of eight international supercomputing facilities, participants were able to undertake the Challenge using dedicated computational resources. Alongside the main challenge, `reproducibility awards' were made in recognition of those pipelines which demonstrated Open Science best practice. The Challenge saw over 100 participants develop a range of new and existing techniques, with results that highlight the strengths of multidisciplinary and collaborative effort. The winning strategy -- which combined predictions from two independent machine learning techniques to yield a 20 percent improvement in overall performance -- underscores one of the main Challenge outcomes: that of method complementarity. It is likely that the combination of methods in a so-called ensemble approach will be key to exploiting very large astronomical datasets.

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arXiv2023

MusE GAs FLOw and Wind (MEGAFLOW) IX. The impact of gas flows on the relations between the mass, star formation rate and metallicity of galaxies

We study the link between gas flow events and key galaxy scaling relations: the relations between star formation rate (SFR) and stellar mass (the main sequence, MS), gas metallicity and stellar mass (the mass-metallicity relation, MZR) and gas metallicity, stellar mass and SFR (the fundamental metallicity relation, FMR). Using all star-forming galaxies (SFGs) in the 22 MUSE fields of the MusE GAs FLOw and Wind (MEGAFLOW) survey, we derive the MS, MZR and FMR scaling relations for 385 SFGs with $M = 10^8 - 10^{11.5}$ $M_\odot$ at redshifts 0.35 < z < 0.85. Using the MUSE data and complementary X-Shooter spectra at 0.85 < z < 1.4, we determine the locations of 21 SFGs associated with inflowing or outflowing circumgalactic gas (i.e. with strong MgII absorption in background quasar spectra) relative to these scaling relations. Compared to a control sample of galaxies without gas flows (i.e., without MgII absorption within 70 kpc of the quasar), SFGs with inflow events (i.e., MgII absorption along the major axis) are preferentially located above the MS, while SFGs with ouflow events (i.e., MgII absorption along the minor axis) are preferentially more metal rich. Our observations support the scenario in which gas accretion increases the SFR while diluting the metal content and where circumgalactic outflows are found in more metal-rich galaxies.

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arXiv2021

The phantom dark matter halos of the Local Volume in the context of modified Newtonian dynamics

We explore the predictions of Milgromian gravity (MOND) in the Local Universe by considering the distribution of the `phantom' dark matter (PDM) that would source the MOND gravitational field in Newtonian gravity, allowing an easy comparison with the dark matter framework. For this, we specifically deal with the quasi-linear version of MOND (QUMOND). We compute the `stellar-to-(phantom)halo-mass relation' (SHMR), a monotonically increasing power-law resembling the SHMR observationally deduced from spiral galaxy rotation curves in the Newtonian context. We show that the gas-to-(phantom)halo-mass relation is flat. We generate a map of the Local Volume in QUMOND, highlighting the important influence of distant galaxy clusters, in particular Virgo. This allows us to explore the scatter of the SHMR and the average density of PDM around galaxies in the Local Volume, $\Omega_{\rm pdm} \approx 0.1$, below the average cold dark matter density in a $\Lambda$CDM Universe. We provide a model of the Milky Way in its external field in the MOND context, which we compare to an observational estimate of the escape velocity curve. Finally, we highlight the peculiar features related to the external field effect in the form of negative PDM density zones in the outskirts of each galaxy, and test a new analytic formula for computing galaxy rotation curves in the presence of an external field in QUMOND. While we show that the negative PDM density zones would be difficult to detect dynamically, we quantify the weak lensing signal they could produce for lenses at $z \sim 0.3$.

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arXiv2021

Probing the radial acceleration relation and the strong equivalence principle with the Coma cluster ultra-diffuse galaxies

The tight radial acceleration relation (RAR) obeyed by rotationally supported disk galaxies is one of the most successful a priori predictions of the modified Newtonian dynamics (MOND) paradigm on galaxy scales. Another important consequence of MOND as a classical modification of gravity is that the strong equivalence principle (SEP) -- which requires the dynamics of a small, free-falling, self-gravitating system not to depend on the external gravitational field in which it is embedded -- should be broken. Multiple tentative detections of this so-called external field effect (EFE) of MOND have been made in the past, but the systems that should be most sensitive to it are galaxies with low internal gravitational accelerations residing in galaxy clusters within a strong external field. Here, we show that ultra-diffuse galaxies (UDGs) in the Coma cluster do lie on the RAR, and that their velocity dispersion profiles are in full agreement with isolated MOND predictions, especially when including some degree of radial anisotropy. However, including a breaking of the SEP via the EFE seriously deteriorates this agreement. We discuss various possibilities to explain this within the context of MOND, including a combination of tidal heating and higher baryonic masses. We also speculate that our results could mean that the EFE is screened in cluster UDGs. The fact that this would happen precisely within galaxy clusters, where classical MOND fails, could be especially relevant to the nature of the residual MOND missing mass in clusters of galaxies.

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arXiv2020

Molecular gas in CLASH brightest cluster galaxies at $z\sim0.2-0.9$

Brightest cluster galaxies (BCGs) are excellent laboratories to study galaxy evolution in dense Mpc-scale environments. We have observed in CO(1-0), CO(2-1), CO(3-2), or CO(4-3), with the IRAM-30m, 18 BCGs at $z\sim0.2-0.9$ that are drawn from the CLASH survey. Our sample includes RX1532, which is our primary target, being among the BCGs with the highest star formation rate (SFR$\gtrsim100~M_\odot$/yr) in the CLASH sample. We unambiguously detected both CO(1-0) and CO(3-2) in RX1532, yielding a large reservoir of molecular gas, $M_{H_2}=(8.7\pm1.1)\times10^{10}~M_\odot$, and a high level of excitation $r_{31}=0.75\pm0.12$. A morphological analysis of the HST I-band image of RX1532 reveals the presence of clumpy substructures both within and outside the half-light radius $r_e=(11.6\pm0.3)$ kpc, similarly to those found independently both in ultraviolet and in H$_\alpha$ in previous work. We tentatively detected CO(1-0) or CO(2-1) in four other BCGs, with molecular gas reservoirs in the range $M_{H_2}=2\times10^{10-11} M_\odot$. For the remaining 13 BCGs we set robust upper limits of $M_{H_2}/M_\star\lesssim0.1$, which are among the lowest molecular gas to stellar mass ratios found for distant ellipticals and BCGs. By comparison with distant cluster galaxies observed in CO our study shows that RX1532 ($M_{H_2}/M_\star = 0.40\pm0.05$) belongs to the rare population of star forming and gas-rich BCGs in the distant universe. By using available X-ray based estimates of the central intra-cluster medium entropy, we show that the detection of large reservoirs of molecular gas $M_{H_2}\gtrsim10^{10}~M_\odot$ in distant BCGs is possible when the two conditions are met: i) high SFR and ii) low central entropy, which favors the condensation and the inflow of gas onto the BCGs themselves, similarly to what has been previously found for some local BCGs.

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arXiv2019

Molecular gas in distant brightest cluster galaxies

The stellar mass assembly of brightest cluster galaxies (BCGs) is still debated. We have observed in CO with the IRAM-30m two star forming BCGs belonging to SpARCS clusters, 3C 244.1 ($z=0.4$) and SDSS J161112.65+550823.5 ($z=0.9$), and compared their molecular gas and star formation properties with those of a compilation of $\sim100$ distant cluster galaxies, including nine additional distant BCGs at ${z\sim0.4-3.5}$. We have set robust upper limits of $M_{{\rm H}_2}<1.0\times10^{10}~M_\odot$ and $<2.8\times10^{10}~M_\odot$ to their molecular gas content, respectively, as well as to the molecular gas to stellar mass ratio $M({\rm H}_2)/M_\star\lesssim0.2$ and depletion time $\tau_{\rm dep}\lesssim40$ Myr of the two targeted BCGs. They are thus among the distant cluster galaxies with the lowest gas fractions and shortest depletion times. The majority, $64\%\pm15\%$ and $73\%\pm18\%$, of the 11 BCGs with observations in CO have lower $M({\rm H}_2)/M_\star$ and $\tau_{\rm dep}$, respectively, than those estimated for main sequence galaxies. Statistical analysis tentatively suggests that the values of $M({\rm H}_2)/M_\star$ and $\tau_{\rm dep}$ for the 11 BCGs deviates, with a significance of $\sim2\sigma$, from those of the comparison sample of cluster galaxies. A morphological analysis for a subsample of seven BCGs with archival HST observations reveals that $71\%\pm17\%$ of the BCGs are compact or show star-forming substructures/components. Our results suggest a scenario where distant star forming BCGs assemble a significant fraction $\sim16\%$ of their stellar mass in the relatively short timescale $\tau_{\rm dep}$, while environmental mechanisms might prevent the replenishment of gas feeding the star formation. We speculate that compact components favor the rapid exhaustion of molecular gas and help to quench the BCGs. Distant star forming BCGs are excellent targets for ALMA and JWST.

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arXiv2018

Molecular gas in radio galaxies in dense Mpc-scale environments at $z=0.4-2.6$

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.

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arXiv2018

PHIBSS2: survey design and z=0.5-0.8 results. Molecular gas reservoirs during the winding-down of star formation

Following the success of the Plateau de Bure high-z Blue Sequence Survey (PHIBSS), we present the PHIBSS2 legacy program, a survey of the molecular gas properties of star-forming galaxies on and around the star formation main sequence (MS) at different redshifts using NOEMA. This survey significantly extends the existing sample of star-forming galaxies with CO molecular gas measurements, probing the peak epoch of star formation (z=1-1.6) as well as its building-up (z=2-3) and winding-down (z=0.5-0.8) phases. The targets are drawn from the GOODS, COSMOS, and AEGIS deep fields and uniformly sample the MS in the stellar mass (M*) - star formation rate (SFR) plane with log(M*/Msun) = 10-11.8. We describe the survey strategy and sample selection before focusing on the results obtained at z=0.5-0.8, where we report 60 CO(2-1) detections out of 61 targets. We determine their molecular gas masses and separately obtain disc sizes and bulge-to-total (B/T) luminosity ratios from HST I-band images. The median molecular gas-to-stellar mass ratio, gas fraction, and depletion time as well as their dependence with M* and offset from the MS follow published scaling relations for a much larger sample of galaxies spanning a wider range of redshifts. The galaxy-averaged Kennicutt-Schmidt (KS) relation between molecular gas and SFR surface densities is strikingly linear, pointing towards similar star formation timescales within galaxies at any given epoch. In terms of morphology, the molecular gas content, the SFR, the disc stellar mass, and the disc molecular gas fraction do not seem to correlate with B/T and the stellar surface density, which suggests an ongoing supply of fresh molecular gas to compensate for the build-up of the bulge. Our measurements do not yield any significant variation of the depletion time with B/T and hence no strong evidence for morphological quenching within the scatter of the MS.

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arXiv2018

Molecular gas in radio galaxies at $z=0.4-2.6$ in (proto-)cluster environment

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.

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arXiv2018

The Molecular and Ionized Gas Phases of an AGN-driven Outflow in a Typical Massive Galaxy at z=2

Nuclear outflows driven by accreting massive black holes are one of the main feedback mechanisms invoked at high-z to reproduce the distinct separation between star-forming, disk galaxies and quiescent spheroidal systems. Yet, our knowledge of feedback at high-z remains limited by the lack of observations of the multiple gas phases in galaxy outflows. In this work we use new deep, high-spatial resolution ALMA CO(3-2) and archival VLT/SINFONI H$\alpha$ observations to study the molecular and ionized components of the AGN-driven outflow in zC400528 ---a massive, main sequence galaxy at z=2.3 in the process of quenching. We detect a powerful molecular outflow that shows a positive velocity gradient and extends for at least ~10 kpc from the nuclear region, about three times the projected size of the ionized wind. The molecular gas in the outflow does not reach velocities high enough to escape the galaxy and is therefore expected to be reaccreted. Keeping in mind the various assumptions involved in the analysis, we find that the mass and energetics of the outflow are dominated by the molecular phase. The AGN-driven outflow in zC400528 is powerful enough to deplete the molecular gas reservoir on a timescale at least twice shorter than that needed to exhaust it by star formation. This suggests that the nuclear outflow is one of the main quenching engines at work in the observed suppression of the central star-formation activity in zC400528.

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arXiv2017

PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions

This paper provides an update of our previous scaling relations (Genzel et al.2015) between galaxy integrated molecular gas masses, stellar masses and star formation rates, in the framework of the star formation main-sequence (MS), with the main goal to test for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ~1mm dust photometry, in a large sample of 1444 star forming galaxies (SFGs) between z=0 and 4. The sample covers the stellar mass range log(M*/M_solar)=9.0-11.8, and star formation rates relative to that on the MS, delta_MS=SFR/SFR(MS), from 10^{-1.3} to 10^{2.2}. Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time t_depl, defined as the ratio of molecular gas mass to star formation rate, scales as (1+z)^{-0.6}x(delta_MS)^{-0.44}, and is only weakly dependent on stellar mass. The ratio of molecular-to-stellar mass mu_gas depends on (1+z)^{2.5}x (delta_MS)^{0.52}x(M*)^{-0.36}, which tracks the evolution of the specific star formation rate. The redshift dependence of mu_gas requires a curvature term, as may the mass-dependences of t_depl and mu_gas. We find no or only weak correlations of t_depl and mu_gas with optical size R or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high-z.

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