arXiv subjects

Philip Hopkins

Publications and source records attributed to Philip Hopkins.

At least 19 recordsLinked to original sources

arXiv2026

Resolving galaxy formation in the early Universe with BonFIRE and CampFIRE

The abundance and rapid growth of galaxies at cosmic dawn revealed by the James Webb Space Telescope challenges models of galaxy formation, motivating new simulations to uncover the processes driving early galaxy assembly. We present the first results from BonFIRE ($L\approx40$ cMpc, $m_{\rm baryon}\approx5\times10^4~\rm{M}_{\odot}$) and CampFIRE ($L\approx5$ cMpc, at both $m_{\rm baryon}\approx800~\rm{M}_{\odot}$ and $\approx6\times10^3~\rm{M}_{\odot}$), a suite of cosmological hydrodynamic simulations of early galaxy formation ($z\gtrsim6$) from the Feedback In Realistic Environments (FIRE) project, using the FIRE-3 model. We use a resampling procedure to combine the large statistics of BonFIRE with the higher resolution of CampFIRE and robustly predict galaxy properties over a wide dynamic range ($M_{\star}\sim10^4-10^{10}~\rm{M}_{\odot}$). Galaxy formation in this suite emerges through clustered, bursty star formation, with halo-scale star formation efficiencies reaching $10-30\%$ in high-mass halos. A subset of low-mass halos also have surprisingly high efficiencies of $\gtrsim1\%$ and host ultra-compact galaxies with narrow age spreads. We predict galaxy UV luminosity functions at $9\lesssim~z\lesssim25$ in broad agreement with observations at $M_{\rm UV}\gtrsim-19$, with a faint-end turnover at $M_{\rm UV}\approx-14$, but we slightly overpredict the abundance of brighter galaxies. We find that UV luminosity variability in early galaxies is strongly mass-dependent, with halo-to-halo scatter dominating at low masses and contributing comparably to rapid temporal burstiness at $M_{\rm halo}\gtrsim10^{10}~\rm{M}_{\odot}$. We also present first results from a simple Pop~III model with a top-heavy IMF, demonstrating broad agreement with independent Pop~III predictions and observational constraints.

astro-ph.GA↗

arXiv2023

Predicting the Radiation Field of Molecular Clouds using Denoising Diffusion Probabilistic Models

Accurately quantifying the impact of radiation feedback in star formation is challenging. To address this complex problem, we employ deep learning techniques, denoising diffusion probabilistic models (DDPMs), to predict the interstellar radiation field (ISRF) strength based on three-band dust emission at 4.5 \um, 24 \um, and 250 \um. We adopt magnetohydrodynamic simulations from the STARFORGE (STAR FORmation in Gaseous Environments) project that model star formation and giant molecular cloud (GMC) evolution. We generate synthetic dust emission maps matching observed spectral energy distributions in the Monoceros R2 (MonR2) GMC. We train DDPMs to estimate the ISRF using synthetic three-band dust emission. The dispersion between the predictions and true values is within a factor of 0.1 for the test set. We extended our assessment of the diffusion model to include new simulations with varying physical parameters. While there is a consistent offset observed in these out-of-distribution simulations, the model effectively constrains the relative intensity to within a factor of 2. Meanwhile, our analysis reveals weak correlation between the ISRF solely derived from dust temperature and the actual ISRF. We apply our trained model to predict the ISRF in MonR2, revealing a correspondence between intense ISRF, bright sources, and high dust emission, confirming the model's ability to capture ISRF variations. Our model robustly predicts radiation feedback distribution, even in complex, poorly constrained ISRF environments like those influenced by nearby star clusters. However, precise ISRF predictions require an accurate training dataset mirroring the target molecular cloud's unique physical conditions.

astro-ph.GA↗

arXiv2022

The impact of cosmic rays on dynamical balance and disk-halo interaction in Lstar disk galaxies

Cosmic rays (CRs) are an important component in the interstellar medium (ISM), but their effect on the dynamics of the disk-halo interface (< 10 kpc from the disk) is still unclear. We study the influence of CRs on the gas above the disk with high-resolution FIRE-2 cosmological simulations of late-type Lstar galaxies at redshift around zero. We compare runs with and without CR feedback (with constant anisotropic diffusion around 3e29 cm^2/s and streaming). Our simulations capture the relevant disk halo interactions, including outflows, inflows, and galactic fountains. Extra-planar gas in all of the runs satisfies dynamical balance, where total pressure balances the weight of the overlying gas. While the kinetic pressure from non-uniform motion (>1-kpc scale) dominates in the midplane, thermal and bulk pressures (or CR pressure if included) take over at large heights. We find that with CR feedback, (1) the warm (1e4K) gas is slowly accelerated by CRs; (2) the hot (> 5e5K) gas scale height is suppressed; (3) the warm-hot (2e4-5e5K) medium becomes the most volume-filling phase in the disk-halo interface. We develop a novel conceptual model of the near-disk gas dynamics in low-redshift Lstar galaxies: With CRs, the disk-halo interface is filled with CR-driven warm winds and hot super-bubbles that are propagating into the CGM with a small fraction falling back to the disk. Without CRs, most outflows from hot superbubbles are trapped by the existing hot halo and gravity, so typically they form galactic fountains.

astro-ph.GA↗

arXiv2021

The central densities of Milky Way-mass galaxies in cold and self-interacting dark matter models

We present a suite of baryonic cosmological zoom-in simulations of self-interacting dark matter (SIDM) haloes within the ``Feedback In Realistic Environment'' (FIRE) project. The three simulated haloes have virial masses of $\sim 10^{12}\, \text{M}_\odot$ at $z=0$, and we study velocity-independent self-interaction cross sections of 1 and 10 ${\rm cm^2 \, g^{-1}}$. We study star formation rates and the shape of dark matter density profiles of the parent haloes in both cold dark matter (CDM) and SIDM models. Galaxies formed in the SIDM haloes have higher star formation rates at $z\leq1$, resulting in more massive galaxies compared to the CDM simulations. While both CDM and SIDM simulations show diverse shape of the dark matter density profiles, the SIDM haloes can reach higher and more steep central densities within few kpcs compared to the CDM haloes. We identify a correlation between the build-up of the stars within the half-mass radii of the galaxies and the growth in the central dark matter densities. The thermalization process in the SIDM haloes is enhanced in the presence of a dense stellar component. Hence, SIDM haloes with highly concentrated baryonic profiles are predicted to have higher central dark matter densities than the CDM haloes. Overall, the SIDM haloes are more responsive to the presence of a massive baryonic distribution than their CDM counterparts.

astro-ph.GA↗

arXiv2021

Cosmological simulations of quasar fueling to sub-parsec scales using Lagrangian hyper-refinement

We present cosmological hydrodynamic simulations of a quasar-mass halo ($M_{\rm halo} \approx 10^{12.5}\,{\rm M}_{\odot}$ at z=2) that for the first time resolve gas transport down to the inner 0.1 pc surrounding the central massive black hole. We model a multi-phase interstellar medium including stellar feedback by supernovae, stellar winds, and radiation, and a hyper-Lagrangian refinement technique increasing the resolution dynamically approaching the black hole. We do not include black hole feedback. We show that the sub-pc inflow rate (1) can reach ~6 M$_{\odot}$yr$^{-1}$ roughly in steady state during the epoch of peak nuclear gas density (z~2), sufficient to power a luminous quasar, (2) is highly time variable in the pre-quasar phase, spanning 0.001-10 M$_{\odot}$yr$^{-1}$ on Myr timescales, and (3) is limited to short (~2 Myr) active phases (0.01-0.1 M$_{\odot}$yr$^{-1}$) followed by longer periods of inactivity at lower nuclear gas density and late times (z~1), owing to the formation of a hot central cavity. Inflowing gas is primarily cool, rotational support dominates over turbulence and thermal pressure, and star formation can consume as much gas as provided by inflows across 1 pc - 10 kpc. Gravitational torques from multi-scale stellar non-axisymmetries dominate angular momentum transport over gas self-torquing and pressure gradients, with accretion weakly dependent on black hole mass. Sub-pc inflow rates correlate with nuclear (but decouple from global) star formation and can exceed the Eddington rate by x10. The black hole can move ~10 pc from the galaxy center on ~0.1 Myr. Accreting gas forms pc-scale, rotationally supported, obscuring structures often misaligned with the galaxy-scale disk. These simulations open a new avenue to investigate black hole-galaxy co-evolution.

astro-ph.GA↗

arXiv2020

The Origin and Evolution of Lyman-alpha Blobs in Cosmological Galaxy Formation Simulations

High-redshift Lyman-alpha blobs (LABs) are an enigmatic class of objects that have been the subject of numerous observational and theoretical investigations. It is of particular interest to determine the dominant power sources for the copious luminosity, as direct emission from HII regions, cooling gas, and fluorescence due to the presence of active galactic nuclei (AGN) can all contribute significantly. In this paper, we present the first theoretical model to consider all of these physical processes in an attempt to develop an evolutionary model for the origin of high-z LABs. This is achieved by combining a series of high-resolution cosmological zoom-in simulations with ionization and Lyman-alpha (Lya) radiative transfer models. We find that massive galaxies display a range of Lya luminosities and spatial extents (which strongly depend on the limiting surface brightness used) over the course of their lives, though regularly exhibit luminosities and sizes consistent with observed LABs. The model LABs are typically powered from a combination of recombination in star-forming galaxies, as well as cooling emission from gas associated with accretion. When AGN are included in the model, the fluorescence caused by AGN-driven ionization can be a significant contributor to the total Lya luminosity as well. We propose that the presence of an AGN may be predicted from the Gini coefficient of the blob's surface brightness. Within our modeled mass range, there are no obvious threshold physical properties that predict appearance of LABs, and only weak correlations of the luminosity with the physical properties of the host galaxy. This is because the emergent Lya luminosity from a system is a complex function of the gas temperature, ionization state, and Lya escape fraction.

astro-ph.GA↗

arXiv2019

Astro2020 Science White Paper: Physical Conditions in the Cold Gas of Local Galaxies

We describe a next major frontier in observational studies of galaxy evolution and star formation: linking the physical conditions in the cold, star-forming interstellar medium to host galaxy and local environment. The integrated gas content of galaxies has been surveyed extensively over the last decades. The link between environment and cold gas density, turbulence, excitation, dynamical state, and chemical makeup remain far less well understood. We know that these properties do vary dramatically and theoretical work posits a strong connection between the state of the gas, its ability to form stars, and the impact of stellar feedback. A next major step in the field will be to use sensitive cm-, mm-, and submm-wave spectroscopy and high resolution spectroscopic imaging to survey the state of cold gas across the whole local galaxy population. Such observations have pushed the capabilities of the current generation of telescopes. We highlight three critical elements for progress in the next decade: (1) robust support and aggressive development of ALMA, (2) the deployment of very large heterodyne receiver arrays on single dish telescopes, and (3) development of a new interferometric array that dramatically improves on current capabilities at cm- and mm-wavelengths (~ 1-115 GHz).

astro-ph.GA↗

arXiv2018

Dating glacier ice of the last millennium by quantum technology

Radiometric dating with 39Ar covers a unique timespan and offers key advances in interpreting environmental archives of the last millennium. Although this tracer has been acknowledged for decades, studies so far have been limited by the low abundance and radioactivity, thus requiring huge sample sizes. Atom Trap Trace Analysis, an application of techniques from quantum physics such as laser cooling and trapping, allows to reduce the sample volume by several orders of magnitude, compared to conventional techniques. Here we show that the adaptation of this method to 39Ar is now available for glaciological applications, by demonstrating the first Argon Trap Trace Analysis (ArTTA) dating of alpine glacier ice samples. Ice blocks as small as a few kilograms are sufficient and have been obtained at two artificial glacier caves. Importantly, both sites offer direct access to the stratigraphy at the glacier base and validation against existing age constraints. The ice blocks obtained at Chli Titlis glacier in 3030 m all (Swiss Alps) have been dated by state-of-the-art micro-radiocarbon analysis in a previous study. The unique finding of a bark fragment and a larch needle within the ice of Schaufelferner glacier in 2870 m asl (Stubai Alps, Austria) allows for conventional radiocarbon dating. At both sites, results of 39Ar dating match the existing age information based on radiocarbon dating and visual stratigraphy. With our results, we establish Argon Trap Trace Analysis as the key to decipher so far untapped glacier archives of the last millennium.

physics.app-ph↗

arXiv2018

Predicting the binary black hole population of the Milky Way with cosmological simulations

Binary black holes are the primary endpoint of massive stellar evolution. Their properties provide a unique opportunity to constrain binary evolution, which is still poorly understood. In this paper, we predict the inventory of binary black holes and their merger products in/around the Milky Way, and detail their main properties. We present the first combination of a high-resolution cosmological simulation of a Milky Way-mass galaxy with a binary population synthesis model. The hydrodynamic simulation, taken from the FIRE project, provides a cosmologically realistic star formation history for the galaxy and its stellar halo and satellites. We apply a metallicity-dependent evolutionary model to the star particles to produce individual binary black holes. We find that a million binary black holes have merged in the model Milky Way, and 3 million binaries are still present, with an average mass of 28 Msun per binary. Because the black hole progenitors are biased towards low metallicity stars, half reside in the stellar halo and satellites and 40 per cent of the binaries were formed outside the main galaxy. This trend increases with the masses of the black holes. The numbers and mass distribution of the merged systems is compatible with the LIGO/Virgo detections. Observations of these black holes will be challenging, both with electromagnetic methods and LISA. We find that a cosmologically realistic star formation history, with self-consistent metal enrichment and Galactic accretion history, are key ingredients for determining binary black hole rates that can be compared with observations to constrain massive binary evolution.

astro-ph.GA↗

arXiv2018

What drives the evolution of gas kinematics in star-forming galaxies?

One important result from recent large integral field spectrograph (IFS) surveys is that the intrinsic velocity dispersion of galaxies traced by star-forming gas increases with redshift. Massive, rotation-dominated discs are already in place at z~2, but they are dynamically hotter than spiral galaxies in the local Universe. Although several plausible mechanisms for this elevated velocity dispersion (e.g. star formation feedback, elevated gas supply, or more frequent galaxy interactions) have been proposed, the fundamental driver of the velocity dispersion enhancement at high redshift remains unclear. We investigate the origin of this kinematic evolution using a suite of cosmological simulations from the FIRE (Feedback In Realistic Environments) project. Although IFS surveys generally cover a wider range of stellar masses than in these simulations, the simulated galaxies show trends between intrinsic velocity dispersion, SFR, and redshift in agreement with observations. In both the observed and simulated galaxies, intrinsic velocity dispersion is positively correlated with SFR. Intrinsic velocity dispersion increases with redshift out to z~1 and then flattens beyond that. In the FIRE simulations, intrinsic velocity dispersion can vary significantly on timescales of <100 Myr. These variations closely mirror the time evolution of the SFR and gas inflow rate. By cross-correlating pairs of intrinsic velocity dispersion, gas inflow rate, and SFR, we show that increased gas inflow leads to subsequent enhanced star formation, and enhancements in intrinsic velocity dispersion tend to temporally coincide with increases in gas inflow rate and SFR.

astro-ph.GA↗

arXiv2018

What FIREs Up Star Formation: the Emergence of the Kennicutt-Schmidt Law from Feedback

We present an analysis of the global and spatially-resolved Kennicutt-Schmidt (KS) star formation relation in the FIRE (Feedback In Realistic Environments) suite of cosmological simulations, including halos with $z = 0$ masses ranging from $10^{10}$ -- $10^{13}$ M$_{\odot}$. We show that the KS relation emerges and is robustly maintained due to the effects of feedback on local scales regulating star-forming gas, independent of the particular small-scale star formation prescriptions employed. We demonstrate that the time-averaged KS relation is relatively independent of redshift and spatial averaging scale, and that the star formation rate surface density is weakly dependent on metallicity and inversely dependent on orbital dynamical time. At constant star formation rate surface density, the `Cold \& Dense' gas surface density (gas with $T < 300$~K and $n > 10$~cm$^{-3}$, used as a proxy for the molecular gas surface density) of the simulated galaxies is $\sim$0.5~dex less than observed at $\sim$kpc scales. This discrepancy may arise from underestimates of the local column density at the particle-scale for the purposes of shielding in the simulations. Finally, we show that on scales larger than individual giant molecular clouds, the primary condition that determines whether star formation occurs is whether a patch of the galactic disk is thermally Toomre-unstable (not whether it is self-shielding): once a patch can no longer be thermally stabilized against fragmentation, it collapses, becomes self-shielding, cools, and forms stars, regardless of epoch or environment.

astro-ph.GA↗

arXiv2016

When and where did GW150914 form?

The recent LIGO detection of gravitational waves (GW150914), likely originating from the merger of two $\sim 30 M_\odot$ black holes suggests progenitor stars of low metallicity ($[Z/Z_\odot] \lesssim 0.3$), constraining when and where the progenitor of GW150914 may have formed. We combine estimates of galaxy properties (metallicity, star formation rate and merger rate) across cosmic time to predict the low redshift black hole - black hole merger rate as a function of present day host galaxy mass, $M_\mathrm{gal}$, and the formation redshift of the progenitor system $z_\mathrm{form}$ for different progenitor metallicities $Z_\mathrm{c}$. At $Z_\mathrm{c}=0.1 Z_\odot$, the signal is dominated by binaries in massive galaxies with $z_\mathrm{form}\simeq 2$, with a small contribution from binaries formed around $z_\mathrm{form}\simeq 0.5$ in dwarf galaxies. For $Z_\mathrm{c}=0.01Z_\odot$, fast mergers are possible and very recent star formation in dwarfs likely dominates. Additional gravitational wave detections from merging massive black holes will provide constraints on the mass-metallicity relation and massive star formation at high redshifts.

astro-ph.HE↗

arXiv2015

The Formation of Submillimetre-Bright Galaxies from Gas Infall over a Billion Years

Submillimetre-luminous galaxies at high-redshift are the most luminous, heavily star-forming galaxies in the Universe, and are characterised by prodigious emission in the far-infrared at 850 microns (S850 > 5 mJy). They reside in halos ~ 10^13Msun, have low gas fractions compared to main sequence disks at a comparable redshift, trace complex environments, and are not easily observable at optical wavelengths. Their physical origin remains unclear. Simulations have been able to form galaxies with the requisite luminosities, but have otherwise been unable to simultaneously match the stellar masses, star formation rates, gas fractions and environments. Here we report a cosmological hydrodynamic galaxy formation simulation that is able to form a submillimetre galaxy which simultaneously satisfies the broad range of observed physical constraints. We find that groups of galaxies residing in massive dark matter halos have rising star formation histories that peak at collective rates ~ 500-1000 Msun/yr at z=2-3, by which time the interstellar medium is sufficiently enriched with metals that the region may be observed as a submillimetre-selected system. The intense star formation rates are fueled in part by a reservoir gas supply enabled by stellar feedback at earlier times, not through major mergers. With a duty cycle of nearly a gigayear, our simulations show that the submillimetre-luminous phase of high-z galaxies is a drawn out one that is associated with significant mass buildup in early Universe proto-clusters, and that many submillimetre-luminous galaxies are actually composed of numerous unresolved components (for which there is some observational evidence).

astro-ph.GA↗

arXiv2013

Why is the Milky Way X-factor Constant?

The CO-H2 conversion factor (Xco; otherwise known as the X-factor) is observed to be remarkably constant in the Milky Way and in the Local Group (aside from the SMC). To date, our understanding of why Xco should be so constant remains poor. Using a combination of extremely high resolution (~ 1 pc) galaxy evolution simulations and molecular line radiative transfer calculations, we suggest that Xco displays a narrow range of values in the Galaxy due to the fact that molecular clouds share very similar physical properties. In our models, this is itself a consequence of stellar feedback competing against gravitational collapse. GMCs whose lifetimes are regulated by radiative feedback show a narrow range of surface densities, temperatures and velocity dispersions with values comparable to those seen in the Milky Way. As a result, the X-factors from these clouds show reasonable correspondence with observed data from the Local Group, and a relatively narrow range. On the other hand, feedback-free clouds collapse to surface densities that are larger than those seen in the Galaxy, and hence result in X-factors that are systematically too large compared to the Milky Way's. We conclude that radiative feedback within GMCs can generate cloud properties similar to those observed in the Galaxy, and hence a roughly constant Milky Way X-factor in normal, quiescent clouds.

astro-ph.GA↗

arXiv2010

Constraints on Black Hole Growth, Quasar Lifetimes, and Eddington Ratio Distributions from the SDSS Broad Line Quasar Black Hole Mass Function

We present an estimate of the black hole mass function (BHMF) of broad line quasars (BLQSOs) that self-consistently corrects for incompleteness and the statistical uncertainty in the mass estimates, based on a sample of 9886 quasars at 1 < z < 4.5 drawn from the Sloan Digital Sky Survey. We find evidence for `cosmic downsizing' of black holes in BLQSOs, where the peak in their number density shifts to higher redshift with increasing black hole mass. The cosmic mass density for black holes seen as BLQSOs peaks at z ~ 2. We estimate the completeness of the SDSS as a function of black hole mass and Eddington ratio, and find that at z > 1 it is highly incomplete at M_BH < 10^9 M_Sun and L / L_Edd < 0.5. We also estimate a lower limit on the lifetime of a single BLQSO phase and we place constraints on the maximum mass of a black hole in a BLQSO. Our estimated distribution of BLQSO Eddington ratios peaks at L / L_Edd ~ 0.05 and has a dispersion of ~ 0.4 dex, implying that most BLQSOs are not radiating at or near the Eddington limit; however the location of the peak is subject to considerable uncertainty. The steep increase in number density of BLQSOs toward lower Eddington ratios is expected if the BLQSO accretion rate monotonically decays with time. Furthermore, our estimated lifetime and Eddington ratio distributions imply that the majority of the most massive black holes spend a significant amount of time growing in an earlier obscured phase, a conclusion which is independent of the unknown obscured fraction. These results are consistent with models for self-regulated black hole growth, at least for massive systems at z > 1, where the BLQSO phase occurs at the end of a fueling event when black hole feedback unbinds the accreting gas, halting the accretion flow.

astro-ph.CO↗

arXiv2010

Self-Regulated Black Hole Growth via Momentum Deposition in Galaxy Merger Simulations

We perform hydrodynamical simulations of major galaxy mergers using new methods for calculating the growth of massive black holes (BH) in galactic nuclei and their impact on the surrounding galaxy. We model BH growth by including a subgrid model for accretion produced by angular momentum transport on unresolved scales. The impact of the BHs radiation on surrounding gas is approximated by depositing momentum into the ambient gas, which produces an outward force away from the BH. We argue that these phenomenological models for BH growth and feedback better approximate the interaction between the BH and dense gas in galaxies than previous models. We show that this physics leads to self-regulated black hole growth: during the peak of activity, the accretion rate onto the BH is largely determined by the physics of BH feedback, not the subgrid accretion model. The BH significantly modifies the gas dynamics in the galactic nucleus (< 300 pc), but does not generate large-scale galactic outflows. Integrated over an entire galaxy merger, BH feedback has little effect on the total number of stars formed, but is crucial for setting the BHs mass.

astro-ph.CO↗

arXiv2010

A Physical Model for z~2 Dust Obscured Galaxies

We present a physical model for the origin of z~2 Dust-Obscured Galaxies (DOGs), a class of high-redshift ULIRGs selected at 24 micron which are particularly optically faint (24/R>1000). By combining N-body/SPH simulations of high redshift galaxy evolution with 3D polychromatic dust radiative transfer models, we find that luminous DOGs (with F24 > 0.3 mJy at z~2 are well-modeled as extreme gas-rich mergers in massive (~5x10^12-10^13 Msun) halos, with elevated star formation rates (~500-1000 Msun/yr) and/or significant AGN growth (Mdot > 0.5 Msun/yr), whereas less luminous DOGs are more diverse in nature. At final coalescence, merger-driven DOGs transition from being starburst dominated to AGN dominated, evolving from a "bump" to a power-law shaped mid-IR (IRAC) spectral energy distribution (SED). After the DOG phase, the galaxy settles back to exhibiting a "bump" SED with bluer colors and lower star formation rates. While canonically power-law galaxies are associated with being AGN-dominated, we find that the power-law mid-IR SED can owe both to direct AGN contribution, as well as to a heavily dust obscured stellar bump at times that the galaxy is starburst dominated. Thus power-law galaxies can be either starburst or AGN dominated. Less luminous DOGs can be well-represented either by mergers, or by massive ($M_{\rm baryon} ~5x10^11 Msun) secularly evolving gas-rich disc galaxies (with SFR > 50 Msun/yr). By utilising similar models as those employed in the SMG formation study of Narayanan et al. (2010), we investigate the connection between DOGs and SMGs. We find that the most heavily star-forming merger driven DOGs can be selected as Submillimetre Galaxies (SMGs), while both merger-driven and secularly evolving DOGs typically satisfy the BzK selection criteria.

astro-ph.CO↗

arXiv2008

The Role of Galactic Winds on Molecular Gas Emission from Galaxy Mergers

We assess the impact of starburst and AGN feedback-driven winds on the CO emission from galaxy mergers, and, in particular, search for signatures of these winds in the simulated CO morphologies and emission line profiles. We do so by combining a 3D non-LTE molecular line radiative transfer code with smoothed particle hydrodynamics (SPH) simulations of galaxy mergers that include prescriptions for star formation, black hole growth, a multiphase interstellar medium (ISM), and the winds associated with star formation and black hole growth. Our main results are: (1) Galactic winds can drive outflows of masses ~10^8-10^9 Msun which may be imaged via CO emission line mapping. (2) AGN feedback-driven winds are able to drive imageable CO outflows for longer periods of time than starburst-driven winds owing to the greater amount of energy imparted to the ISM by AGN feedback compared to star formation. (3) Galactic winds can control the spatial extent of the CO emission in post-merger galaxies, and may serve as a physical motivation for the sub-kiloparsec scale CO emission radii observed in local advanced mergers. (4) Secondary emission peaks at velocities greater than the circular velocity are seen in the CO emission lines in all models. In models with winds, these high velocity peaks are seen to preferentially correspond to outflowing gas entrained in winds, which is not the case in the model without winds. The high velocity peaks seen in models without winds are typically confined to velocity offsets (from the systemic) < 1.7 times the circular velocity, whereas the models with AGN feedback-driven winds can drive high velocity peaks to ~2.5 times the circular velocity.

astro-ph↗