Galaxy kinematics during the peak epoch of cosmic star formation

Diese Arbeit befasst sich mit der Kinematik von Sterne bildenden Galaxien (SFGs) während der Hochzeit der kosmischen Sternentstehung, bei Rotverschiebungen 0.5<z<3. Basierend auf den genommenen Beobachtungen wird abgeleitet, welche Massenkomponenten die Galaxien dynamisch stabilisieren, und wie sich deren Beitrag im Laufe von 6 Milliarden Jahren verändert. Um einen Zusammenhang zwischen einerseits der beobachtbaren Masse in der Form von Sternen und Gas und andererseits der Dunklen Materie in Galaxien herzustellen, werden die Tully-Fisher-Beziehungen genutzt. Es zeigt sich, dass die dynamische Stabilität der SFGs bei z~2.3 durch Gas und Sterne dominiert wird, während bei z~0.9 Dunkle Materie relevanter wird. Bei gleichbleibender Kreisgeschwindigkeit haben SFGs bei z~2.3 und z~0.9 die gleiche stellare Masse, aber ihre Gasmasse ist bei höherer Rotverschiebung größer. Auf der Grundlage von vorhandenen Modellen der Galaxienentwicklung wird ein Toy-Modell entwickelt, das die zeitlichen Änderung in der stellaren und gasförmigen Masse typischer SFGs in Betracht zieht, um die beobachtete, nicht-monotone Entwicklung der Tully-Fisher-Beziehungen von z~2.3 bis z=0 zu erklären. Durch die graduelle Umwandlung von Gas zu Sternen verändert sich das interstellare Medium und dessen Einfluss auf die Galaxienkinematik. Die Entwicklung der intrinsischen Geschwindigkeitsdispersion des ionisierten Gases in typischen SFGs wird diskutiert sowie die Streuung und mögliche Ursachen dieser turbulenten Bewegungen. Durch Beobachtungsdaten sowie theoretische Überlegungen wird gezeigt, dass die galaktische Turbulenz bei z>2 höchstwahrscheinlich durch gravitative Instabilitäten dominiert wird, während diese zu späterer kosmischer Zeit weniger bedeutsam werden, und so der Einfluss von stellaren Feedbackprozessen an Relevanz gewinnen kann. Eine genauere Analyse der Kinematik individueller, massiver SFGs wird vorgenommen, um die Beiträge sichtbarer und Dunkler Materie zur Galaxiendynamik mit höherer räumlicher Auflösung und bis zu größeren galaktischen Radien zu untersuchen. Besonders bei z>2 finden sich sehr turbulente und extrem baryonisch dominierte Systeme mit fallenden Rotationskurven auf der Basis von ionisiertem Gas. In einer detaillierten Fallstudie, die Messungen des ionisierten sowie molekularen Gases kombiniert, wird gezeigt, dass die Kinematik dieser beiden Gasphasen ausgezeichnet übereinstimmt. Dieses Ergebnis ist eine wichtige Demonstration dessen, dass die Bewegungen des ionisiertes Gases das Gravitationspotential abbilden. Durch einen Vergleich der Beobachtungsdaten mit modernen kosmologischen Simulationen werden Unterschiede im Gasgehalt und in der Kinematik massiver z~2 SFGs identifiziert, die vermutlich auf Unzulänglichkeiten in den Simulationen aufgrund nicht aufgelöster physikalischer Prozesse im interstellaren Medium und deren Implementierung hinweisen.In this thesis we discuss the kinematics of star-forming galaxies (SFGs) during the peak epoch of cosmic star formation rate density, at redshifts 0.5<z<3. Based on our observations, we deduce information on their mass budget and dynamical support, and we follow its evolution over 6 billion years of cosmic history. We use the Tully-Fisher relations to connect the observable stellar and total baryonic mass to dark matter on galactic scales, and find that at z~2.3 the galactic dynamical support is dominated by gas and stellar mass, while at z~0.9 dark matter becomes more important. At fixed circular velocity, SFGs have the same amount of stellar mass at z~2.3 and z~0.9, but their gas masses are higher at higher redshift. Based on existing models of galaxy evolution, we develop a toy model taking into account changes in the stellar and gas content of typical SFGs, to explain the observed, non-monotonic evolution of the Tully-Fisher relations from z~2.6 to z=0. Through the gradual conversion of gas into stars, the dynamical state of the interstellar medium and its impact on the galaxy kinematics changes. We discuss the evolution of the intrinsic velocity dispersion of ionized gas in typical SFGs, its scatter, and possible mechanisms driving these turbulent motions. Based on both observational and theoretical evidence we conclude that at z>2 gas turbulence is likely dominated by gravitational instabilities, while towards lower redshift these mechanisms become less important and therefore the impact of stellar feedback may become comparable. We zoom in on the kinematics of individual, massive SFGs to investigate in more detail the dynamical contributions of luminous and dark matter with higher spatial resolution and out to larger galactic radii. Especially at z>2 we find very turbulent, strongly baryon-dominated systems with dropping outer rotation curves traced by ionized gas emission. In a detailed case study combining measurements from ionized and molecular gas, we show that the observed kinematics in both tracers are in excellent agreement. This result is an important demonstration that the ionized gas reliably traces the gravitational potential. Through comparison of our observations with modern cosmological simulations, we identify differences in gas content and kinematics of massive z~2 SFGs that likely point towards shortcomings in the simulations introduced by unresolved physics in the interstellar medium, and their implementation via sub-grid recipes

Galaxy kinematics during the peak epoch of cosmic star formation

Diese Arbeit befasst sich mit der Kinematik von Sterne bildenden Galaxien (SFGs) während der Hochzeit der kosmischen Sternentstehung, bei Rotverschiebungen 0.5<z<3. Basierend auf den genommenen Beobachtungen wird abgeleitet, welche Massenkomponenten die Galaxien dynamisch stabilisieren, und wie sich deren Beitrag im Laufe von 6 Milliarden Jahren verändert. Um einen Zusammenhang zwischen einerseits der beobachtbaren Masse in der Form von Sternen und Gas und andererseits der Dunklen Materie in Galaxien herzustellen, werden die Tully-Fisher-Beziehungen genutzt. Es zeigt sich, dass die dynamische Stabilität der SFGs bei z~2.3 durch Gas und Sterne dominiert wird, während bei z~0.9 Dunkle Materie relevanter wird. Bei gleichbleibender Kreisgeschwindigkeit haben SFGs bei z~2.3 und z~0.9 die gleiche stellare Masse, aber ihre Gasmasse ist bei höherer Rotverschiebung größer. Auf der Grundlage von vorhandenen Modellen der Galaxienentwicklung wird ein Toy-Modell entwickelt, das die zeitlichen Änderung in der stellaren und gasförmigen Masse typischer SFGs in Betracht zieht, um die beobachtete, nicht-monotone Entwicklung der Tully-Fisher-Beziehungen von z~2.3 bis z=0 zu erklären. Durch die graduelle Umwandlung von Gas zu Sternen verändert sich das interstellare Medium und dessen Einfluss auf die Galaxienkinematik. Die Entwicklung der intrinsischen Geschwindigkeitsdispersion des ionisierten Gases in typischen SFGs wird diskutiert sowie die Streuung und mögliche Ursachen dieser turbulenten Bewegungen. Durch Beobachtungsdaten sowie theoretische Überlegungen wird gezeigt, dass die galaktische Turbulenz bei z>2 höchstwahrscheinlich durch gravitative Instabilitäten dominiert wird, während diese zu späterer kosmischer Zeit weniger bedeutsam werden, und so der Einfluss von stellaren Feedbackprozessen an Relevanz gewinnen kann. Eine genauere Analyse der Kinematik individueller, massiver SFGs wird vorgenommen, um die Beiträge sichtbarer und Dunkler Materie zur Galaxiendynamik mit höherer räumlicher Auflösung und bis zu größeren galaktischen Radien zu untersuchen. Besonders bei z>2 finden sich sehr turbulente und extrem baryonisch dominierte Systeme mit fallenden Rotationskurven auf der Basis von ionisiertem Gas. In einer detaillierten Fallstudie, die Messungen des ionisierten sowie molekularen Gases kombiniert, wird gezeigt, dass die Kinematik dieser beiden Gasphasen ausgezeichnet übereinstimmt. Dieses Ergebnis ist eine wichtige Demonstration dessen, dass die Bewegungen des ionisiertes Gases das Gravitationspotential abbilden. Durch einen Vergleich der Beobachtungsdaten mit modernen kosmologischen Simulationen werden Unterschiede im Gasgehalt und in der Kinematik massiver z~2 SFGs identifiziert, die vermutlich auf Unzulänglichkeiten in den Simulationen aufgrund nicht aufgelöster physikalischer Prozesse im interstellaren Medium und deren Implementierung hinweisen.In this thesis we discuss the kinematics of star-forming galaxies (SFGs) during the peak epoch of cosmic star formation rate density, at redshifts 0.5<z<3. Based on our observations, we deduce information on their mass budget and dynamical support, and we follow its evolution over 6 billion years of cosmic history. We use the Tully-Fisher relations to connect the observable stellar and total baryonic mass to dark matter on galactic scales, and find that at z~2.3 the galactic dynamical support is dominated by gas and stellar mass, while at z~0.9 dark matter becomes more important. At fixed circular velocity, SFGs have the same amount of stellar mass at z~2.3 and z~0.9, but their gas masses are higher at higher redshift. Based on existing models of galaxy evolution, we develop a toy model taking into account changes in the stellar and gas content of typical SFGs, to explain the observed, non-monotonic evolution of the Tully-Fisher relations from z~2.6 to z=0. Through the gradual conversion of gas into stars, the dynamical state of the interstellar medium and its impact on the galaxy kinematics changes. We discuss the evolution of the intrinsic velocity dispersion of ionized gas in typical SFGs, its scatter, and possible mechanisms driving these turbulent motions. Based on both observational and theoretical evidence we conclude that at z>2 gas turbulence is likely dominated by gravitational instabilities, while towards lower redshift these mechanisms become less important and therefore the impact of stellar feedback may become comparable. We zoom in on the kinematics of individual, massive SFGs to investigate in more detail the dynamical contributions of luminous and dark matter with higher spatial resolution and out to larger galactic radii. Especially at z>2 we find very turbulent, strongly baryon-dominated systems with dropping outer rotation curves traced by ionized gas emission. In a detailed case study combining measurements from ionized and molecular gas, we show that the observed kinematics in both tracers are in excellent agreement. This result is an important demonstration that the ionized gas reliably traces the gravitational potential. Through comparison of our observations with modern cosmological simulations, we identify differences in gas content and kinematics of massive z~2 SFGs that likely point towards shortcomings in the simulations introduced by unresolved physics in the interstellar medium, and their implementation via sub-grid recipes

Why stellar feedback promotes disc formation in simulated galaxies

We study how feedback influences baryon infall onto galaxies using cosmological, zoom-in simulations of haloes with present mass $M_{vir}=6.9\times10^{11} M_{\odot}$ to $1.7\times10^{12} M_{\odot}$. Starting at z=4 from identical initial conditions, implementations of weak and strong stellar feedback produce bulge- and disc-dominated galaxies, respectively. Strong feedback favours disc formation: (1) because conversion of gas into stars is suppressed at early times, as required by abundance matching arguments, resulting in flat star formation histories and higher gas fractions; (2) because 50% of the stars form in situ from recycled disc gas with angular momentum only weakly related to that of the z=0 dark halo; (3) because late-time gas accretion is typically an order of magnitude stronger and has higher specific angular momentum, with recycled gas dominating over primordial infall; (4) because 25-30% of the total accreted gas is ejected entirely before z~1, removing primarily low angular momentum material which enriches the nearby inter-galactic medium. Most recycled gas roughly conserves its angular momentum, but material ejected for long times and to large radii can gain significant angular momentum before re-accretion. These processes lower galaxy formation efficiency in addition to promoting disc formation.Comment: 23 pages, 29 figures, accepted for publication in MNRA

The MOSDEF Survey: Kinematic and Structural Evolution of Star-Forming Galaxies at 1.4≤z≤3.81.4\leq z\leq 3.8

We present ionized gas kinematics for 681 galaxies at $z\sim 1.4-3.8$ from the MOSFIRE Deep Evolution Field survey, measured using models which account for random galaxy-slit misalignments together with structural parameters derived from CANDELS Hubble Space Telescope (HST) imaging. Kinematics and sizes are used to derive dynamical masses. Baryonic masses are estimated from stellar masses and inferred gas masses from dust-corrected star formation rates (SFRs) and the Kennicutt-Schmidt relation. We measure resolved rotation for 105 galaxies. For the remaining 576 galaxies we use models based on HST imaging structural parameters together with integrated velocity dispersions and baryonic masses to statistically constrain the median ratio of intrinsic ordered to disordered motion, $V/\sigma_{V,0}$. We find that $V/\sigma_{V,0}$ increases with increasing stellar mass and decreasing specific SFR (sSFR). These trends may reflect marginal disk stability, where systems with higher gas fractions have thicker disks. For galaxies with detected rotation we assess trends between their kinematics and mass, sSFR, and baryon surface density ($\Sigma_{\mathrm{bar},e}$). Intrinsic dispersion correlates most with $\Sigma_{\mathrm{bar},e}$ and velocity correlates most with mass. By comparing dynamical and baryonic masses, we find that galaxies at $z\sim 1.4-3.8$ are baryon dominated within their effective radii ($R_E$), with Mdyn/Mbaryon increasing over time. The inferred baryon fractions within $R_E$, $f_{\mathrm{bar}}$, decrease over time, even at fixed mass, size, or surface density. At fixed redshift, $f_{\mathrm{bar}}$ does not appear to vary with stellar mass but increases with decreasing $R_E$ and increasing $\Sigma_{\mathrm{bar},e}$. For galaxies at $z\geq2$, the median inferred baryon fractions generally exceed 100%. We discuss possible explanations and future avenues to resolve this tension.Comment: Accepted to ApJ. Added Figure 9, corrected sample size (main results unchanged). 28 pages, 13 figure

The Kinematics and Dark Matter Fractions of TNG50 Galaxies at z=2 from an Observational Perspective

We contrast the gas kinematics and dark matter contents of $z=2$ star-forming galaxies (SFGs) from state-of-the-art cosmological simulations within the $\Lambda$CDM framework to observations. To this end, we create realistic mock observations of massive SFGs ($M_*>4\times10^{10} M_{\odot}$, SFR $>50~M_{\odot}$ yr$^{-1}$) from the TNG50 simulation of the IllustrisTNG suite, resembling near-infrared, adaptive-optics assisted integral-field observations from the ground. Using observational line fitting and modeling techniques, we analyse in detail the kinematics of seven TNG50 galaxies from five different projections per galaxy, and compare them to observations of twelve massive SFGs by Genzel et al. (2020). The simulated galaxies show clear signs of disc rotation but mostly exhibit more asymmetric rotation curves, partly due to large intrinsic radial and vertical velocity components. At identical inclination angle, their one-dimensional velocity profiles can vary along different lines of sight by up to $\Delta v=200$ km s$^{-1}$. From dynamical modelling we infer rotation speeds and velocity dispersions that are broadly consistent with observational results. We find low central dark matter fractions compatible with observations ($f_{\rm DM}^v(<R_e)=v_{\rm DM}^2(R_e)/v_{\rm circ}^2(R_e)\sim0.32\pm0.10$), however for disc effective radii $R_e$ that are mostly too small: at fixed $R_e$ the TNG50 dark matter fractions are too high by a factor of $\sim2$. We speculate that the differences in gas kinematics and dark matter content compared to the observations may be due to physical processes that are not resolved in sufficient detail with the numerical resolution available in current cosmological simulations.Comment: 25 pages, 16 figures, accepted for publication in MNRA

Structural Evolution in Massive Galaxies at z ~ 2

We present 0.2arcsec-resolution Atacama Large Millimeter/submillimeter Array observations at 870 $\mu$m in a stellar mass-selected sample of 85 massive ($M_\mathrm{star}>10^{11}~M_\odot$) star-forming galaxies (SFGs) at z=1.9-2.6 in the 3D-HST/CANDELS fields of UDS and GOODS-S. We measure the effective radius of the rest-frame far-infrared (FIR) emission for 62 massive SFGs. They are distributed over wide ranges of FIR size from $R_\mathrm{e,FIR}=$0.4 kpc to $R_\mathrm{e,FIR}=$6 kpc. The effective radius of the FIR emission is smaller by a factor of 2.3$^{+1.9}_{-1.0}$ than the effective radius of the optical emission and by a factor of 1.9$^{+1.9}_{-1.0}$ smaller than the half-mass radius. Even with taking into account potential extended components, the FIR size would change by ~10%. By combining the spatial distributions of the FIR and optical emission, we investigate how galaxies change the effective radius of the optical emission and the stellar mass within a radius of 1 kpc, $M_\mathrm{1kpc}$. The compact starburst puts most of massive SFGs on the mass--size relation for quiescent galaxies (QGs) at z~2 within 300 Myr if the current star formation activity and its spatial distribution are maintained. We also find that within 300 Myr, ~38% of massive SFGs can reach the central mass of $M_\mathrm{1kpc}=10^{10.5}~M_\odot$, which is around the boundary between massive SFGs and QGs. These results suggest an outside-in transformation scenario in which a dense core is formed at the center of a more extended disk, likely via dissipative in-disk inflows. Synchronized observations at ALMA 870 $\mu$m and JWST 3-4 $\mu$m will explicitly verify this scenario.Comment: 25 pages, 15 figures, 3 tables, accepted for publication in Ap

The ionising photon production efficiency at z~6 for a sample of bright Lyman-alpha emitters using JEMS and MUSE

We study the ionising photon production efficiency at the end of the Epoch of Reionisation ($z \sim 5.4 - 6.6$) for a sample of 35 bright Lyman-$\alpha$ emitters, this quantity is crucial to infer the ionising photon budget of the Universe. These objects were selected to have reliable spectroscopic redshifts, assigned based on the profile of their Lyman-$\alpha$ emission line, detected in the MUSE deep fields. We exploit medium-band observations from the JWST extragalactic medium band survey (JEMS) to find the flux excess corresponding to the redshifted \ha\ emission line. We estimate the UV luminosity by fitting the full JEMS photometry, along with several HST photometric points, with \texttt{Prospector}. We find a median ultra-violet continuum slope of $\beta = -2.21^{+0.26}_{-0.17}$ for the sample, indicating young stellar populations with little-to-no dust attenuation. Supported by this, we derive $\xi_{ion,0}$ with no dust attenuation and find a median value of log$\frac{\xi_{ion,0}}{\text{Hz erg}^{-1}} = 26.36^{+0.17}_{-0.14}$. If we perform dust attenuation corrections and assume a Calzetti attenuation law, our values are lowered by $\sim 0.1$ dex. Our results suggest Lyman-$\alpha$ emitters at the Epoch of Reionisation have enhanced $\xi_{ion,0}$ compared to previous estimations from literature, in particular, when compared to the non-Lyman-$\alpha$ emitting population. This initial study provides a promising outlook on the characterisation of ionising photon production in the early Universe. In the future, a more extensive study will be performed on the entire dataset provided by the JWST Advanced Deep Extragalactic Survey (JADES). Thus, for the first time, allowing us toComment: 11 pages, 5 figures in main paper. 10 pages, 30 figures in appendix. Submitted to MNRA

A massive black hole in a low-metallicity AGN at z∼5.55z\sim5.55 revealed by JWST/NIRSpec IFS

We present JWST/NIRSpec Integral Field Spectrograph rest-frame optical data of the compact $z=5.55$ galaxy GS_3073. Its prominent broad components in several hydrogen and helium lines (while absent in the forbidden lines), and the detection of a large equivalent width of He II $\lambda4686$, EW(He II) $\sim20$ Angstrom, unambiguously identify it as an active galactic nucleus (AGN). We measure a gas-phase metallicity of $Z_{\rm gas}/Z_\odot\sim0.21^{+0.08}_{-0.04}$, lower than what has been inferred for both more luminous AGN at similar redshift and lower redshift AGN. We empirically show that classical emission line ratio diagnostic diagrams cannot be used to distinguish between the primary ionisation source (AGN or star formation) for such low-metallicity systems, whereas different diagnostic diagrams involving He II$\lambda4686$ prove very useful, independent of metallicity. We measure the central black hole mass to be $\log(M_{\rm BH}/M_\odot)\sim8.20^{+0.11}_{-0.16}$. While this places GS_3073 at the lower end of known high-redshift black hole masses, it still appears to be over-massive compared to its host galaxy properties. We detect an outflow with projected velocity $\gtrsim700$~km/s and an ionised gas mass outflow rate of about $100\ M_\odot/$yr, suggesting that GS_3073 is able to enrich the intergalactic medium with metals one billion years after the Big Bang.Comment: 15 pages, 10 figures; comments are welcome. Submitted to A&

GA-NIFS: Black hole and host galaxy properties of two z≃\simeq6.8 quasars from the NIRSpec IFU

Integral Field Spectroscopy (IFS) with JWST NIRSpec will significantly improve our understanding of the first quasars, by providing spatially resolved, infrared spectroscopic capabilities which cover key rest-frame optical emission lines that have been previously unobservable. Here we present our results from the first two z>6 quasars observed as a part of the Galaxy Assembly with NIRSpec IFS (GA-NIFS) GTO program, DELS J0411-0907 at z=6.82 and VDES J0020-3653 at z=6.86. By observing the H$\beta$, [OIII], and H$\alpha$ emission lines in these high-z quasars for the first time, we measure accurate black hole masses, $M_{\rm{BH}}=1.85e9$ and $2.9e9$M$_\odot$, corresponding to Eddington ratios of $\lambda_{\rm{Edd}}=0.8$ and 0.4 for DELS J0411-0907 and VDES J0020-3653 respectively. These provide a key comparison for existing estimates from the more uncertain MgII line. We perform quasar-host decomposition using models of the quasars' broad lines to measure the underlying host galaxies. We also discover multiple emission line regions surrounding each of the host galaxies, which are likely companion galaxies undergoing mergers with these hosts. We measure the star formation rates, excitation mechanisms, and dynamical masses of the hosts and companions, measuring the $M_{\rm{BH}}/M_{\rm{dyn}}$ ratios at high-z using these estimators for the first time. DELS J0411-0907 and VDES J0020-3653 both lie above the local black hole--host mass relation, and are consistent with the existing observations of $z\gtrsim6$ quasar host galaxies with ALMA. We detect ionized outflows in [OIII] and H$\beta$ from both quasars, with mass outflow rates of 58 and 525 M$_{\odot}$/yr for DELS J0411-0907 and VDES J0020-3653, much larger than their host star formation rates of <33 and <54 M$_\odot$/yr. This work highlights the exceptional capabilities of the JWST NIRSpec IFU for observing quasars in the early Universe.Comment: 27 pages, 10 figures. Resubmitted to A&A after significant revisions. If you have cited values from our first version, please check this version and update accordingly, as many values have changed slightly thanks to improvements in our analysi

JADES. The diverse population of infant Black Holes at 4<z<11: merging, tiny, poor, but mighty

We present 12 new AGN at 4<z<7 in the JADES survey (in addition to the previously identified AGN in GN-z11 at z=10.6) revealed through the detection of a Broad Line Region as seen in the Balmer emission lines. The depth of JADES, together with the use of three different spectral resolutions, enables us to probe a lower mass regime relative to previous studies. In a few cases we find evidence for two broad components of Halpha which suggests that these could be candidate merging black holes (BHs). The inferred BH masses range between 8 x 10^7 Msun down to 4 x 10^5 Msun, interestingly probing the regime expected for Direct Collapse Black Holes. The inferred AGN bolometric luminosities (~10^44-10^45 erg/s) imply accretion rates that are < 0.5 times the Eddington rate in most cases. However, small BH, with M_BH ~ 10^6 Msun, tend to accrete at Eddington or super-Eddington rates. These BH at z~4-11 are over-massive relative to their host galaxies stellar masses when compared to the local M_BH-Mstar relation. However, we find that these early BH tend to be more consistent with the local relation between M_BH and velocity dispersion, as well as between M_BH and dynamical mass, suggesting that these are more fundamental and universal relations. On the BPT excitation-diagnostic diagram these AGN are located in the region that is that is locally occupied by star-forming galaxies, implying that they would be missed by the standard classification techniques if they did not display broad lines. Their location on the diagram is consistent with what expected for AGN hosted in metal poor galaxies (Z ~ 0.1-0.2 Zsun). The fraction of broad line AGN with L_AGN > 10^44 erg/s, among galaxies in the redshift range 4<z<6, is about 10%, suggesting that the contribution of AGN and their hosts to the reionization of the Universe is > 10%.Comment: Submitted to A&A, 25 pages, 13 figures, 4 table