The BarYon CYCLE Project (ByCycle): Identifying and Localizing MgII Metal Absorbers with Machine Learning

The upcoming ByCycle project on the VISTA/4MOST multi-object spectrograph will offer new prospects of using a massive sample of $\sim 1$ million high spectral resolution ($R$ = 20,000) background quasars to map the circumgalactic metal content of foreground galaxies (observed at $R$ = 4000 - 7000), as traced by metal absorption. Such large surveys require specialized analysis methodologies. In the absence of early data, we instead produce synthetic 4MOST high-resolution fibre quasar spectra. To do so, we use the TNG50 cosmological magnetohydrodynamical simulation, combining photo-ionization post-processing and ray tracing, to capture MgII ($\lambda2796$, $\lambda2803$) absorbers. We then use this sample to train a Convolutional Neural Network (CNN) which searches for, and estimates the redshift of, MgII absorbers within these spectra. For a test sample of quasar spectra with uniformly distributed properties ($\lambda_{\rm{MgII,2796}}$, $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05 - 5.15$ \AA, $\rm{SNR} = 3 - 50$), the algorithm has a robust classification accuracy of 98.6 per cent and a mean wavelength accuracy of 6.9 \AA. For high signal-to-noise spectra ($\rm{SNR > 20}$), the algorithm robustly detects and localizes MgII absorbers down to equivalent widths of $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05$ \AA. For the lowest SNR spectra ($\rm{SNR=3}$), the CNN reliably recovers and localizes EW$_{\rm{MgII,2796}}^{\rm{rest}}$ $\geq$ 0.75 \AA\, absorbers. This is more than sufficient for subsequent Voigt profile fitting to characterize the detected MgII absorbers. We make the code publicly available through GitHub. Our work provides a proof-of-concept for future analyses of quasar spectra datasets numbering in the millions, soon to be delivered by the next generation of surveys.Comment: 13 pages, 9 figures, 1 table. Accepted for publication in MNRA

ALMACAL IX: Multiband ALMA survey for dusty star-forming galaxies and the resolved fractions of the cosmic infrared background

Wide, deep, blind continuum surveys at submillimetre/millimetre (submm/mm) wavelengths are required to provide a full inventory of the dusty, distant Universe. However, conducting such surveys to the necessary depth, with sub-arcsec angular resolution, is prohibitively time-consuming, even for the most advanced submm/mm telescopes. Here, we report the most recent results from the ALMACAL project, which exploits the ‘free’ calibration data from the Atacama Large Millimetre/submillimetre Array (ALMA) to map the lines of sight towards and beyond the ALMA calibrators. ALMACAL has now covered 1001 calibrators, with a total sky coverage around 0.3 deg2, distributed across the sky accessible from the Atacama desert, and has accumulated more than 1000 h of integration. The depth reached by combining multiple visits to each field makes ALMACAL capable of searching for faint, dusty, star-forming galaxies (DSFGs), with detections at multiple frequencies to constrain the emission mechanism. Based on the most up-to-date ALMACAL data base, we report the detection of 186 DSFGs with flux densities down to S870 µm ∼ 0.2 mJy, comparable with existing ALMA large surveys but less susceptible to cosmic variance. We report the number counts at five wavelengths between 870 μm and 3 mm, in ALMA bands 3, 4, 5, 6, and 7, providing a benchmark for models of galaxy formation and evolution. By integrating the observed number counts and the best-fitting functions, we also present the resolved fraction of the cosmic infrared background (CIB) and the CIB spectral shape. Combining existing surveys, ALMA has currently resolved about half of the CIB in the submm/mm regime

MUSE-ALMA Halos XI: Gas flows in the circumgalactic medium

The flow of gas into and out of galaxies leaves traces in the circumgalactic medium which can then be studied using absorption lines towards background quasars. We analyse 27 log(N_HI) > 18.0 HI absorbers at z = 0.2 to 1.4 from the MUSE-ALMA Halos survey with at least one galaxy counterpart within a line of sight velocity of +/-500 km s^{-1}. We perform 3D kinematic forward modelling of these associated galaxies to examine the flow of dense, neutral gas in the circumgalactic medium. From the VLT/MUSE, HST broadband imaging and VLT/UVES and Keck/HIRES high-resolution UV quasar spectroscopy observations, we compare the impact parameters, star-formation rates and stellar masses of the associated galaxies with the absorber properties. We find marginal evidence for a bimodal distribution in azimuthal angles for strong HI absorbers, similar to previous studies of the MgII and OVI absorption lines. There is no clear metallicity dependence on azimuthal angle and we suggest a larger sample of absorbers are required to fully test the relationship predicted by cosmological hydrodynamical simulations. A case-by-case study of the absorbers reveals that ten per cent of absorbers are consistent with gas accretion, up to 30 per cent trace outflows while the remainder trace gas in the galaxy disk, the intragroup medium and low-mass galaxies below the MUSE detection limit. Our results highlight that the baryon cycle directly affects the dense neutral gas required for star-formation and plays a critical role in galaxy evolution.Comment: 13 pages, 6 figures, 12 pages of appendix. Accepted for publication in MNRA

MUSE-ALMA Haloes IX: Morphologies and Stellar Properties of Gas-rich Galaxies

Understanding how galaxies interact with the circumgalactic medium (CGM) requires determining how galaxies morphological and stellar properties correlate with their CGM properties. We report an analysis of 66 well-imaged galaxies detected in HST and VLT MUSE observations and determined to be within $\pm$500 km s$^{-1}$ of the redshifts of strong intervening quasar absorbers at $0.2 \lesssim z \lesssim 1.4$ with H I column densities $N_{\rm H I}$ $>$ $10^{18}$ $\rm cm^{-2}$. We present the geometrical properties (S\'ersic indices, effective radii, axis ratios, and position angles) of these galaxies determined using GALFIT. Using these properties along with star formation rates (SFRs, estimated using the H$\alpha$ or [O II] luminosity) and stellar masses ($M_{*}$ estimated from spectral energy distribution fits), we examine correlations among various stellar and CGM properties. Our main findings are as follows: (1) SFR correlates well with $M_{*}$, and most absorption-selected galaxies are consistent with the star formation main sequence (SFMS) of the global population. (2) More massive absorber counterparts are more centrally concentrated and are larger in size. (3) Galaxy sizes and normalized impact parameters correlate negatively with $N_{\rm H I}$, consistent with higher $N_{\rm H I}$ absorption arising in smaller galaxies, and closer to galaxy centers. (4) Absorption and emission metallicities correlate with $M_{*}$ and sSFR, implying metal-poor absorbers arise in galaxies with low past star formation and faster current gas consumption rates. (5) SFR surface densities of absorption-selected galaxies are higher than predicted by the Kennicutt-Schmidt relation for local galaxies, suggesting a higher star formation efficiency in the absorption-selected galaxies.Comment: Accepted for publication in MNRAS, 25 pages, 19 figure

Cool and cold gas within and surrounding galaxies

Galaxies are systems evolving through a combination of internal processes and their connection to their immediate surroundings. Mechanisms, such as Active Galactic Nuclei (AGN) feedback, stellar feedback, recycling of gas, and accretion from the cosmic web lead to a redistribution of baryons within and surrounding galaxies. These processes interact in the multi-phase Circumgalactic Medium (CGM), defined as the gas surrounding galaxies outside the disk or interstellar medium (ISM), but within the virial radius of galaxies. Thus, the CGM allows for the tracing of gas flows, which are particularly significant in the context of galaxy evolution and star formation. The removal of gas by violent feedback processes could lead to the quenching of star formation, while accretion is critical to sustaining star formation. The accreted gas mixes with the matter within galaxies and can subsequently cool down and then collapse into molecular clouds, leading to the formation of stars. Thus, the CGM, the cold gas phase, and its precursor, the cool gas phase, play key roles in how galaxies evolve across cosmic time. The goal of this thesis is to explore the cool and cold gas phases, encompassing molecular, neutral atomic, and low-ionized atomic gas within and surrounding galaxies across cosmic time. Exploiting multi-phase observations of the MUSE-ALMA Haloes survey we study the cold molecular gas of a HI-absorption-selected galaxy. Additionally, we trace gas flows in the CGM by kinematically analyzing the low-ionized and molecular gas of a galaxy at z ~ 0.4 in emission and absorption. We find that the ionized and molecular gas phases are strongly coupled within the rotating disk of the galaxy and that a two-component absorption feature at 52 kpc distance from the galaxy is consistent with being inflowing and co-rotating gas. Further, a comprehensive literature compilation of HI-absorption and emission-selected galaxies at z < 1.1 reveals that HI-absorption selection of galaxies possibly traces objects that have large molecular gas reservoirs given their star formation rate. This leads to depletion times that can be over an order of magnitude larger than the median depletion times in samples of emission-selected galaxies. Observations of the cold gas phase across cosmic time indicate a marked increase in the molecular gas mass density towards z ~ 2-3. This transformation implies an accompanied change in the global distribution of molecular hydrogen H2 column densities, which is currently not yet explored. To tackle this question, we use an approach that bridges observations (PHANGS-ALMA, SDSS) and simulations (Illustris Project, GRIFFIN Project) to explore this evolution of molecular gas column densities. This study reveals that the H2 column density contributing most to the overall molecular gas mass evolves with redshift. We find that more molecular gas is found in denser regions at z=3 compared to z=0. This finding is consistent with a higher star formation rate density at z=3, as more molecular gas in denser states is likely contributing to a higher global star formation rate. Further, comparisons of the distribution of HI and H2 column densities lead to the conclusion that HI is an important contributor to the overall cold gas mass found in the ISM of galaxies at both redshifts. Going forward, large-scale spectroscopic absorption-line surveys will offer new prospects for mapping the CGM surrounding galaxies. Such large surveys, as the upcoming VISTA/4MOST High-resolution Quasar survey (4Hi-Q), will require novel analysis tools to efficiently detect and localize these absorption lines in spectra. For this purpose, we develop such a tool based on Convolutional Neural Networks (CNN). In the absence of data, we produce synthetic normalized 4MOST high-resolution fibre quasar spectra and inject MgII (λ2796, λ2803) absorbers based on the TNG50 simulation of the Illustris Project within them. Using these synthetic spectra, we train a CNN to classify whether an MgII absorber is present within spectra and to localize them in wavelength space. The CNN has high classification (98 per cent) and localization (mean absolute error of 6.9 Å) accuracy for a sample with evenly distributed absorber and noise properties. Additionally, this method is orders of magnitude faster than traditional ones. This proof-of-concept study demonstrates that Machine Learning is a feasible tool for future large-scale surveys. In summary, with these three distinct projects, we explore the inner workings of the cosmic baryon cycle and the CGM from the scale of individual galaxies to large statistical samples using an approach that bridges observations and simulations. Additionally, we explore the feasibility of novel methods for the analysis of large-scale surveys to pave the way for the era of big data astronomy.Galaxien sind Systeme, die sich durch eine Kombination aus internen Prozessen und ihrer Verbindung zu ihrer unmittelbaren Umgebung entwickeln. Mechanismen wie die Rückkopplung aktiver galaktischer Kerne (AGN), stellare Rückkopplung, wiederverwertung von Gas und Akkretion aus dem kosmischen Netz führen zu einer Umverteilung von Baryonen innerhalb von Galaxien und in ihrer Umgebung. Diese Prozesse interagieren im mehrphasigen zirkumgalaktischen Medium (CGM), definiert als das Gas, das Galaxien außerhalb der Scheibe oder des interstellaren Mediums (ISM), aber innerhalb des Virialradius der Galaxien umgibt. Das CGM ermöglicht somit die Verfolgung von Gasströmen, die im Zusammenhang mit der Entwicklung von Galaxien und der Sternentstehung von besonderer Bedeutung sind. Die Entfernung von Gas durch gewaltsame Rückkopplungsprozesse könnte zum Erlöschen der Sternentstehung in Galaxien führen, während die Akkretion für die Aufrechterhaltung der Sternentstehung entscheidend ist. Das akkretierte Gas vermischt sich mit der Materie innerhalb der Galaxien und kann anschließend abkühlen und zu Molekülwolken kollabieren, was zur Sternentstehung führt. Somit spielen das CGM, die kalte Gasphase, und ihr Vorläufer, die kühle Gasphase, eine Schlüsselrolle bei der Entwicklung von Galaxien im Laufe der kosmischen Zeit. Ziel dieser Arbeit ist es, die kalte und kühle Gasphase, die das molekulare, neutrale atomare und schwach ionisierte atomare Gas umfasst, in und rundum Galaxien über die kosmische Zeit hinweg zu studieren. Mithilfe von mehrphasigen Beobachtungen der MUSE-ALMA Haloes Survey untersuchen wir das kalte molekulare Gas einer anhand von HI-Absorption selektierten Galaxie bei z ~ 0.4. Zusätzlich verfolgen wir Gasflüsse im CGM durch kinematische Analysen des niedrig ionisierten und molekularen Gases dieser Galaxie, welches in Emission und Absorption beobachtet wurde. Wir stellen fest, dass die Phasen des ionisierten und des molekularen Gases innerhalb der rotierenden Scheibe der Galaxie stark gekoppelt sind, und dass ein zwei komponentiges Absorptionssystem in 52 kpc Entfernung von der Galaxie mit einströmendem und mitrotierendem Gas vereinbar ist. Darüber hinaus zeigt eine umfassende Literaturzusammenstellung von Galaxien (z < 1.1) die einerseits anhand von HI-Absorption und andererseits anhand von Emission selektiert wurden, dass die Auswahl von Galaxien anhand HI-Absorption möglicherweise Objekte aufspürt, die über größere molekulare Gasreservoirs verfügen als andere Galaxien mit vergleichbaren Sternentstehungsraten. Dies führt zu Erschöpfungszeiten des molekularen Gases, die mehr als eine Größenordnung größer sein können als die mittleren Erschöpfungszeiten in Stichproben die anhand von Emission selektiert wurden. Beobachtungen der kalten Gasphase über die kosmische Zeit hinweg deuten auf eine deutliche Zunahme der Massendichte des molekularen Gases in Richtung z ~2-3 hin. Diese Entwicklung impliziert eine damit einhergehende Änderung der globalen Verteilung der Säulendichte von molekularem Wasserstoff (H2) die derzeit noch nicht erforscht ist. Um dieser Frage nachzugehen, verwenden wir einen Ansatz, der Beobachtungen (PHANGS-ALMA, SDSS) und Simulationen (Illustris-Project, GRIFFIN-Project) miteinander verbindet, um die Entwicklung der Säulendichten von molekularem Gas zu untersuchen. Diese Studie zeigt, dass die H2-Säulendichte, die am meisten zur Gesamtmasse des molekularen Gases beiträgt, sich mit der Rotverschiebung entwickelt. Bei z=3 ist mehr molekulares Gas in dichteren Regionen zu finden als bei z=0. Dies steht im Einklang mit einer höheren Dichte der Sternentstehungsrate bei z=3, da mehr molekulares Gas in dichteren Zuständen wahrscheinlich zu einer höheren globalen Sternentstehungsrate beiträgt. Vergleiche der Verteilung der HI und H2-Säulendichten deuten außerdem an, dass HI einen großen Anteil zur Gesamtmasse des kalten Gases im ISM von Galaxien beiträgt. Künftig werden groß angelegte spektroskopische Absorptionslinien-Durchmusterungen neue Perspektiven für die Kartierung des CGM bieten. Solche großen Durchmusterungen, wie die bevorstehende VISTA/4MOST High-resolution Quasar Survey (4Hi-Q), erfordern neuartige Analysewerkzeuge, um diese Absorptionslinien in den Spektren effizient zu erkennen und zu lokalisieren. Zu diesem Zweck entwickeln wir ein solches Werkzeug, das auf Convolutional Neural Networks (CNN) basiert. In Ermangelung von Daten erstellen wir auf dem 4MOST Instrument basierende synthetische normalisierte Quasarspektren und injizieren MgII (λ2796, λ2803) Absorber, die auf der TNG50-Simulation des Illustris-Projects basieren, in diese Spektren. Anhand dieser synthetischen Spektren trainieren wir ein CNN, um zu klassifizieren, ob ein MgII-Absorber in den Spektren vorhanden ist und um deren Wellenlängenposition zu bestimmen. Das CNN hat eine hohe Klassifizierungs- (98 Prozent) und Lokalisierungsgenauigkeit (mittlerer absoluter Fehler von 6.9 Å) für eine Stichprobe mit gleichmäßig verteilten Absorber- und Rauscheigenschaften. Außerdem ist diese Methode um Größenordnungen schneller als herkömmliche Methoden. Diese Machbarkeitsstudie zeigt, dass Machine Learning ein praktikables Werkzeug für zukünftige groß angelegte Durchmusterungen ist. In Zusammenfassung erforschen wir mit diesen drei verschiedenen Projekten das Innenleben des kosmischen Baryonenkreislaufs und des CGM auf einer Skala einzelner Galaxien bis hin zu großen statistischen Stichproben und verfolgen dabei einen Ansatz, der Beobachtungen und Simulationen miteinander verbindet. Außerdem, erproben wir die Verwendbarkeit von Machine Learning für die Analyse groß angelegter Durchmusterungen, um den Weg für die Ära der Big-Data-Astronomie zu ebnen

The column densities of molecular gas across cosmic time: bridging observations and simulations

International audienceObservations of the cosmic evolution of different gas phases across time indicate a marked increase in the molecular gas mass density towards z ~ 2-3. Such a transformation implies an accompanied change in the global distribution of molecular hydrogen column densities ($N_{\rm {H_2}}$). Using observations by PHANGS-ALMA/SDSS and simulations by GRIFFIN/IllustrisTNG we explore the evolution of this H2 column density distribution function [$f(N_{\rm {H}_2})$]. The H2 (and H I) column density maps for TNG50 and TNG100 are derived in post-processing and are made available through the IllustrisTNG online API. The shape and normalization of $f(N_{\rm {H}_2})$ of individual main-sequence star-forming galaxies are correlated with the star formation rate (SFR), stellar mass (M*), and H2 mass ($M_{\rm {H}_2}$) in both observations and simulations. TNG100, combined with H2 post-processing models, broadly reproduces observations, albeit with differences in slope and normalization. Also, an analytically modelled f(N), based on exponential gas discs, matches well with the simulations. The GRIFFIN simulation gives first indications that the slope of $f(N_{\rm {H}_2})$ might not majorly differ when including non-equilibrium chemistry in simulations. The $f(N_{\rm {H}_2})$ by TNG100 implies that higher molecular gas column densities are reached at z = 3 than at z = 0. Further, denser regions contribute more to the molecular mass density at z = 3. Finally, H2 starts dominating compared to H I only at column densities above log($N_{\rm {H}_2} / \rm {cm}^{-2}) \sim 21.8\!-\!22$ at both redshifts. These results imply that neutral atomic gas is an important contributor to the overall cold gas mass found in the ISM of galaxies including at densities typical for molecular clouds at z = 0 and 3

MUSE-ALMA haloes VI: coupling atomic, ionized, and molecular gas kinematics of galaxies

International audienceABSTRACT We present results of MUSE-ALMA haloes, an ongoing study of the circumgalactic medium (CGM) of galaxies (z ≤ 1.4). Using multiphase observations we probe the neutral, ionized, and molecular gas in a subsample containing six absorbers and nine associated galaxies in the redshift range z ∼ 0.3–0.75. Here, we give an in-depth analysis of the newly CO-detected galaxy Q2131−G1 (z = 0.42974), while providing stringent mass and depletion time limits for the non-detected galaxies. Q2131−G1 is associated with an absorber with column densities of log(NH i/cm−2) ∼ 19.5 and $\textrm {log}(N_{\textrm {H}_2}/\textrm {cm}^{-2}) \sim 16.5$, and has a star formation rate of SFR = 2.00 ± 0.20 M⊙yr−1, a dark matter fraction of fDM(r1/2) = 0.24–0.54, and a molecular gas mass of $M_\textrm {mol} = 3.52 ^{+3.95}_{-0.31} \times 10^9 \,\, \textrm {M}_{\odot }$ resulting in a depletion time of τdep &lt; 4.15 Gyr. Kinematic modelling of both the CO (3–2) and [O iii] λ5008 emission lines of Q2131−G1 shows that the molecular and ionized gas phases are well aligned directionally and that the maximum rotation velocities closely match. These two gas phases within the disc are strongly coupled. The metallicity, kinematics, and orientation of the atomic and molecular gas traced by a two-component absorption feature are consistent with being part of the extended rotating disc with a well-separated additional component associated with infalling gas. Compared to emission-selected samples, we find that H i-selected galaxies have high molecular gas masses given their low star formation rate. We consequently derive high depletion times for these objects

The BarYon CYCLE Project (ByCycle): Identifying and Localizing MgII Metal Absorbers with Machine Learning

International audienceThe upcoming ByCycle project on the VISTA/4MOST multi-object spectrograph will offer new prospects of using a massive sample of $\sim 1$ million high spectral resolution ($R$ = 20,000) background quasars to map the circumgalactic metal content of foreground galaxies (observed at $R$ = 4000 - 7000), as traced by metal absorption. Such large surveys require specialized analysis methodologies. In the absence of early data, we instead produce synthetic 4MOST high-resolution fibre quasar spectra. To do so, we use the TNG50 cosmological magnetohydrodynamical simulation, combining photo-ionization post-processing and ray tracing, to capture MgII ($\lambda2796$, $\lambda2803$) absorbers. We then use this sample to train a Convolutional Neural Network (CNN) which searches for, and estimates the redshift of, MgII absorbers within these spectra. For a test sample of quasar spectra with uniformly distributed properties ($\lambda_{\rm{MgII,2796}}$, $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05 - 5.15$Å, $\rm{SNR} = 3 - 50$), the algorithm has a robust classification accuracy of 98.6 per cent and a mean wavelength accuracy of 6.9 Å. For high signal-to-noise spectra ($\rm{SNR > 20}$), the algorithm robustly detects and localizes MgII absorbers down to equivalent widths of $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05$Å. For the lowest SNR spectra ($\rm{SNR=3}$), the CNN reliably recovers and localizes EW$_{\rm{MgII,2796}}^{\rm{rest}}$$\geq$ 0.75 Å absorbers. This is more than sufficient for subsequent Voigt profile fitting to characterize the detected MgII absorbers. We make the code publicly available through GitHub. Our work provides a proof-of-concept for future analyses of quasar spectra datasets numbering in the millions, soon to be delivered by the next generation of surveys

The BarYon CYCLE Project (ByCycle): Identifying and Localizing MgII Metal Absorbers with Machine Learning

International audienceThe upcoming ByCycle project on the VISTA/4MOST multi-object spectrograph will offer new prospects of using a massive sample of $\sim 1$ million high spectral resolution ($R$ = 20,000) background quasars to map the circumgalactic metal content of foreground galaxies (observed at $R$ = 4000 - 7000), as traced by metal absorption. Such large surveys require specialized analysis methodologies. In the absence of early data, we instead produce synthetic 4MOST high-resolution fibre quasar spectra. To do so, we use the TNG50 cosmological magnetohydrodynamical simulation, combining photo-ionization post-processing and ray tracing, to capture MgII ($\lambda2796$, $\lambda2803$) absorbers. We then use this sample to train a Convolutional Neural Network (CNN) which searches for, and estimates the redshift of, MgII absorbers within these spectra. For a test sample of quasar spectra with uniformly distributed properties ($\lambda_{\rm{MgII,2796}}$, $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05 - 5.15$Å, $\rm{SNR} = 3 - 50$), the algorithm has a robust classification accuracy of 98.6 per cent and a mean wavelength accuracy of 6.9 Å. For high signal-to-noise spectra ($\rm{SNR > 20}$), the algorithm robustly detects and localizes MgII absorbers down to equivalent widths of $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05$Å. For the lowest SNR spectra ($\rm{SNR=3}$), the CNN reliably recovers and localizes EW$_{\rm{MgII,2796}}^{\rm{rest}}$$\geq$ 0.75 Å absorbers. This is more than sufficient for subsequent Voigt profile fitting to characterize the detected MgII absorbers. We make the code publicly available through GitHub. Our work provides a proof-of-concept for future analyses of quasar spectra datasets numbering in the millions, soon to be delivered by the next generation of surveys