arXiv subjects

Ignacio Martin-Navarro

Publications and source records attributed to Ignacio Martin-Navarro.

18 recordsLinked to original sources

arXiv2024

Observational constraints on the stellar recycled gas in active galactic nuclei feeding

Near-infrared long-slit spectroscopy has been used to study the stellar population (SP) of the low luminosity active galactic nuclei (AGN) and matched analogues (LLAMA) sample. To perform the SP fits we have employed the X-shooter simple stellar population models together with the \st\ code. Our main conclusions are: The star formation history of the AGNs is very complex, presenting many episodes of star formation during their lifetimes. In general, AGN hosts have higher fractions of intermediate-age SP (light-weighted mean ages, $ _L\lesssim$ 4.5 Gyr) when compared with their analogues ($ _L\lesssim$ 8.0 Gyr). AGN are more affected by reddening and require significant fractions of featureless continuum and hot dust components. The ratio between the AGN radiated energy and the gravitational potential energy of the molecular gas ($E_{Rad}$/$E_{PG}$) for the AGN is compared with the \maL\ and a possible anti-correlation is observed. This suggests that the AGN is affecting the star formation in these galaxies, in the sense that more energetic AGN (log$(E_{Rad}$/$E_{PG}) \gtrsim 3$) tend to host nuclear younger SP ($ _L \lesssim$4Gyr). We found that the recent ($t<$2~Gyr) returned (recycled) stellar mass is higher in AGN than in the controls. We also provide evidence that the mass loss of stars would be enough to feed the AGN, thus providing observational constraints for models that predict that AGN feeding is partially due to the recycled gas from dying stars.

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arXiv2024

Baryonic properties of nearby galaxies across the stellar-to-total dynamical mass relation

In the standard cosmological model, the assembly of galaxies is primarily driven by the growth of their host dark matter halos. At the center of these halos, however, baryonic processes take over, leading to the plethora of observed galaxy properties. The coupling between baryonic and dark matter physics is central to our understanding of galaxies and yet, it remains a challenge for theoretical models and observations. Here, we demonstrate that measured ages, metallicities, stellar angular momentum, morphology and star formation rates, correlate with both stellar and halo mass. Using dynamical modeling, we find that at fixed stellar mass, CALIFA galaxies become younger, more metal-poor and rotationally supported, have higher star formation rates and later-type morphologies as their total mass increases, with independent stellar and total masses measurements. These results indicate that the formation of galaxies and thus their baryonic properties do not vary with stellar mass alone, with halo mass also playing an important role.

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arXiv2022

The dark side of galaxy stellar populations II: The dependence of star formation histories on halo mass and on the scatter of the main sequence

Nearby galaxies are the end result of their cosmological evolution, which is predicted to be influenced by the growth of their host dark matter halos. This co-evolution potentially leaves signatures in present-day observed galaxy properties, which might be essential to further understand how the growth and properties of galaxies are connected to those of their host halos. In this work, we study the evolutionary histories of nearby galaxies both in terms of their host halos and the scatter of the star-forming main sequence by investigating their time-resolved stellar populations using absorption optical spectra drawn from the Sloan Digital Sky Survey. We find that galaxy star formation histories depend on the masses of their host halos, and hence they shape the evolution of the star-forming main sequence over cosmic time. Additionally, we also find that the scatter around the z=0 star-forming main sequence is not (entirely) stochastic, as galaxies with currently different star formation rates have experienced, on average, different star formation histories. Our findings suggest that dark matter halos might play a key role in modulating the evolution of star formation in galaxies, and thus of the main sequence, and further demonstrate that galaxies at different evolutionary stages contribute to the observed scatter of this relation.

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arXiv2022

The black hole population in low-mass galaxies in large-scale cosmological simulations

Recent systematic searches for massive black holes (BHs) in local dwarf galaxies led to the discovery of a population of faint Active Galactic Nuclei (AGN). We investigate the agreement of the BH and AGN populations in the Illustris, TNG, Horizon-AGN, EAGLE, and SIMBA simulations with current observational constraints in low-mass galaxies. We find that some of these simulations produce BHs that are too massive, and that the BH occupation fraction at z=0 is not inherited from the simulation seeding modeling. The ability of BHs and their host galaxies to power an AGN depends on BH and galaxy subgrid modeling. The fraction of AGN in low-mass galaxies is not used to calibrate the simulations, and thus can be used to differentiate galaxy formation models. AGN fractions at z=0 span two orders of magnitude at fixed galaxy stellar mass in simulations, similarly to observational constraints, but uncertainties and degeneracies affect both observations and simulations. The agreement is difficult to interpret due to differences in the masses of simulated and observed BHs, BH occupation fraction affected by numerical choices, and an unknown fraction of obscured AGN. Our work advocates for more thorough comparisons with observations to improve the modeling of cosmological simulations, and our understanding of BH and galaxy physics in the low-mass regime. The mass of BHs, their ability to efficiently accrete gas, and the AGN fraction in low-mass galaxies have important implications for the build-up of the entire BH and galaxy populations with time.

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arXiv2022

The dark side of galaxy stellar populations I: The stellar-to-halo mass relation and the velocity dispersion - halo mass relation

The growth and properties of galaxies are thought to be closely connected to the ones of their host dark matter halos. Despite the importance of this so-called galaxy-halo connection, the potential role of dark matter halos in regulating observed galaxy properties remains yet to be fully understood. In this work, we derive the ages, metallicites and [Mg/Fe] abundances from optical spectra from the Sloan Digital Sky Survey of nearby central galaxies, and study them in terms of their host halos. We investigate how the scatter in the stellar-to-halo mass relation and the velocity dispersion - halo mass relation correlates with these stellar population parameters. In addition, we also study the differences when distinguishing between different galaxy morphologies and environments. We find that the ages and chemical enrichment of galaxies are not fully determined by their stellar masses or velocity dispersion, but also depend on the mass of the host halos. Our findings suggest that the velocity dispersion is the best proxy of the stellar population parameters with halo mass playing a secondary yet noticeable role. We interpret that the origin of the correlation between the scatter of these relations and the ages and metallicities might be related to different halo formation times.

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arXiv2021

X-ray bubbles in the circumgalactic medium of TNG50 Milky Way- and M31-like galaxies: signposts of supermassive black hole activity

The TNG50 cosmological simulation produces X-ray emitting bubbles, shells, and cavities in the circumgalactic gas above and below the stellar disks of Milky Way- and Andromeda-like galaxies with morphological features reminiscent of the eROSITA and Fermi bubbles in the Galaxy. Two-thirds of the 198 MW/M31 analogues inspected in TNG50 at z=0 show one or more large-scale, coherent features of over-pressurized gas that impinge into the gaseous halo. Some of the galaxies include a succession of bubbles or shells of increasing size, ranging from a few to many tens of kpc. These are prominent in gas pressure, X-ray emission and gas temperature, and often exhibit sharp boundaries with typical shock Mach numbers of 2-4. The gas in the bubbles outflows with maximum (95th pctl) radial velocities of 100-1500 km/s. TNG50 bubbles expand with speeds as high as 1000-2000 km/s (about 1-2 kpc/Myr), but with a great diversity and with larger bubbles expanding at slower speeds. The bubble gas is at 10^6.4-7.2 K temperatures and is enriched to metallicities of 0.5-2 solar. In TNG50, the bubbles are a manifestation of episodic, kinetic, wind-like energy injections from the supermassive black holes at the galaxy centers that accrete at low Eddington ratios. According to TNG50, X-ray, and possibly gamma-ray, bubbles similar to those observed in the Milky Way should be a frequent feature of disk-like galaxies prior to, or on the verge of, being quenched. They should be within the grasp of eROSITA in the local Universe.

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arXiv2021

Rejuvenation triggers nuclear activity in nearby galaxies

Feedback, in particular from active galactic nuclei (AGN), is believed to play a crucial role in the evolution of galaxies. In the local Universe, many galaxies with an AGN are indeed observed to reside in the so-called green valley, usually interpreted as a transition phase from a blue star-forming to a red quenched state. We use data from the Sloan Digital Sky Survey to show that such an interpretation requires substantial revision. Optically-selected nearby AGN galaxies follow exponentially declining star formation histories, as normal galaxies of similar stellar and dark matter halo mass, reaching in the recent past ($\sim$0.1 Gyr ago) star formation rate levels consistent with a quiescent population. However, we find that local AGN galaxies have experienced a sudden increase in their star formation rate, unfolding on timescales similar to those typical of AGN activity, suggesting that both star formation and AGN activity were triggered simultaneously. We find that this quenching followed by an enhancement in the star formation rate is common to AGN galaxies and more pronounced in early type galaxies. Our results demonstrate that local AGN galaxies are not just a simple transition type between star-forming and quiescent galaxies as previously postulated.

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arXiv2020

Kinematic signatures of nuclear discs and bar-driven secular evolution in nearby galaxies of the MUSE TIMER project

The central regions of disc galaxies hold clues to the processes that dominate their formation and evolution. The TIMER project has obtained high signal-to-noise and spatial resolution integral-field spectroscopy data of the inner few kpc of 21 nearby massive barred galaxies, allowing studies of the stellar kinematics with unprecedented spatial resolution. We confirm theoretical predictions of the effects of bars on stellar kinematics, and identify box/peanuts through kinematic signatures in mildly and moderately inclined galaxies, finding a lower limit to the fraction of massive barred galaxies with box/peanuts at ~62%. Further, we provide kinematic evidence of the connection between barlenses, box/peanuts and bars. We establish the presence of nuclear discs in 19 galaxies and show that their kinematics are characterised by near-circular orbits with low pressure support, and are consistent with the bar-driven secular evolution picture for their formation. In fact, we show that these nuclear discs have, in the region where they dominate, larger rotational support than the underlying main galaxy disc. We define a kinematic radius for the nuclear discs and show that it relates to bar radius, ellipticity and strength, and bar-to-total ratio. Comparing our results with photometric studies, we find that state-of-the-art galaxy image decompositions are able to discern nuclear discs from classical bulges, if the images employed have enough physical spatial resolution. In fact, we show that nuclear discs are typically identified in such image decompositions as photometric bulges with (near-)exponential profiles. However, we find that the presence of composite bulges (galaxies hosting both a classical bulge and a nuclear disc) can often be unnoticed in studies based on photometry alone, and suggest a more stringent threshold to the Sersic index to identify galaxies with pure classical bulges.

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arXiv2020

Reconstructing the mass accretion histories of nearby Red Nuggets with their globular cluster systems

It is generally recognized that massive galaxies form through a combination of in-situ collapse and ex-situ accretion. The in-situ component forms early, where gas collapse and compaction leads to the formation of massive compact systems (blue and red "nuggets") seen at $z>1$. The subsequent accretion of satellites brings in ex-situ material, growing these nuggets in size and mass to appear as the massive early-type galaxies (ETGs) we see locally. Due to stochasticity in the accretion process, in a few rare cases a red nugget will evolve to the present day having undergone little ex-situ mass accretion. The resulting massive, compact and ancient objects have been termed "relic galaxies". Detailed stellar population and kinematic analyses are required to characterise these systems. However, an additional crucial aspect lies in determining the fraction of ex-situ mass they have accreted since their formation. Globular cluster systems can be used to constrain this fraction, since the oldest and most metal-poor globular clusters in massive galaxies are primarily an accreted, ex-situ population. Models for the formation of relic galaxies and their globular cluster systems suggest that, due to their early compaction and limited accretion of dark-matter dominated satellites, relic galaxies should have characteristically low dark-matter mass fractions compared to ETGs of the same stellar mass.

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arXiv2019

Black hole feedback and the evolution of massive early-type galaxies

Observationally, constraining the baryonic cycle within massive galaxies has proven to be quite difficult. In particular, the role of black hole feedback in regulating star formation, a key process in our theoretical understanding of galaxy formation, remains highly debated. We present here observational evidence showing that, at fixed stellar velocity dispersion, the temperature of the hot gas is higher for those galaxies hosting more massive black holes in their centers. Analyzed in the context of well-established scaling relations, particularly the mass-size plane, the relation between the mass of the black hole and the temperature of the hot gas around massive galaxies provides further observational support to the idea that baryonic processes within massive galaxies are regulated by the combined effects of the galaxy halo virial temperature and black hole feedback, in agreement with the expectations from the EAGLE cosmological numerical simulation.

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arXiv2019

Quantifying the effect of black hole feedback from the central galaxy on the satellite populations of groups and clusters

Super-massive black holes are fundamental ingredients in our theoretical understanding of galaxy formation. They are likely the only sources energetic enough to regulate star formation within massive dark matter halos, but observational evidence of this process remains elusive. The effect of black hole feedback is expected to be a strong function of halo mass, and galaxy groups and clusters are among the most massive structures in the Universe. At fixed halo mass, we find an enhanced fraction of quiescent satellite galaxies and a hotter X-ray intragroup and intracluster medium in those groups and clusters hosting more massive black holes in their centers. These results indicate that black hole feedback makes quenching processes more efficient through a cumulative heating of the gaseous intragroup and intracluster medium.

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arXiv2019

Extreme chemical abundance ratio suggesting an exotic origin for an ultra-diffuse galaxy

Ultra diffuse galaxies are a population of extended galaxies but with relatively low luminosities. The origin of these objects remains unclear, largely due to the observational challenges of the low surface brightness Universe. We present here a detailed stellar population analysis of a relatively isolated UDG, DGSAT I, based on spectroscopic data from the Keck Cosmic Web Imager integral field unit. The star formation history of DGSAT I seems to be extended, with a mean luminosity-weighted age of ~3 Gyr, in agreement with previous photometric studies. However, we find a very high [Mg/Fe] abundance ratio, which is extreme even in the context of the highly alpha-enhanced massive ellipticals and ultra-faint dwarfs. The [Mg/Fe]-enhancement of DGSAT I appears to be 10 times higher than the most magnesium-enhanced stellar systems discovered to date, and suggests that the chemical enrichment of this object was dominated by core-collapse supernovae. Intriguingly, this breaks the canonical relation between [Mg/Fe] and star formation time-scale. With a measured velocity dispersion of 56 +/- 10 km/s, DGSAT I also shows a high mass-to-light ratio, which indicates that it is highly dark matter-dominated. The metal-poor conditions of DGSAT I may have enhanced the formation of massive stars, while at the same time, additional mechanisms are needed to prevent iron-rich yields from being recycled into stars. These results suggest that some ultra-diffuse galaxies could have experienced chemical enrichment episodes similar to the first building blocks of galaxies.

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arXiv2018

History and destiny of an emerging early-type galaxy: New IFU insights on the major-merger remnant NGC7252

NGC7252, which is one of the nearest major-merger galaxy remnants, is an ideal laboratory to study the processes inherent to the transformation of disc galaxies to ellipticals as observed about ~1Gyr after the collision. We obtained wide-field IFU spectroscopy with the VLT-VIMOS integral-field spectrograph covering the central 50"x50" of NGC7252 to map the stellar and ionised gas kinematics, and the distribution and conditions of the ionised gas, revealing the extent of ongoing star formation and recent star formation history. We find that the inner gas disc is not counter-rotating with respect to the stars and that the stellar kinematics appear complex with a clear indication of a prolate-like rotation component suggesting a polar merger configuration. The ongoing star formation rate is 2.2+-0.6 M_sun/yr and implies a typical depletion time of 2Gyr given the molecular gas content. Furthermore, the spatially-resolved star formation history suggests a slight radial dependence, moving outwards at later times. We confirm a large AGN-ionised gas cloud previously discovered 5kpc south of the nucleus, and find higher ionisation also at the galaxy centre relative to the surrounding gas disc. Although the higher ionisation towards the centre is potentially degenerate within the central star forming ring, it may be associated with a low-luminosity AGN. Although NGC7252 has been classified as post-starburst galaxy at the centre, the elliptical-like major-merger remnant still appears very active. A central kpc-scale gas disc has presumably re-formed quickly within the last 100Myr after final coalescence. The disc features ongoing star formation, implying Gyr long timescale to reach the red sequence through gas consumption alone. While NGC7252 is useful to probe the transformation from discs to ellipticals, it is not well-suited to study the transformation from blue to red at this point.

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arXiv2018

Origins of ultra-diffuse galaxies in the Coma cluster II. Constraints from their stellar populations

In this second paper of the series, we study with new Keck/DEIMOS spectra the stellar populations of seven spectroscopically confirmed ultra-diffuse galaxies (UDGs) in the Coma cluster. We find intermediate to old ages (~ 7Gyr), low metallicities ([Z/H] ~ -0.7dex) and mostly super-solar abundance patterns ([Mg/Fe] ~ 0.13dex). These properties are similar to those of low-luminosity (dwarf) galaxies inhabiting the same area in the cluster and are most consistent with being the continuity of the stellar mass scaling relations of more massive galaxies. These UDGs' star formation histories imply a relatively recent infall into the Coma cluster, consistent with the theoretical predictions for a dwarf-like origin. However, considering the scatter in the resulting properties and including other UDGs in Coma, together with the results from the velocity phase-space study of the Paper I in this series, a mixed-bag of origins is needed to explain the nature of all UDGs. Our results thus reinforce a scenario in which many UDGs are field dwarfs that become quenched through their later infall onto cluster environments, whereas some UDGs could be genuine primordial galaxies that failed to develop due to an early quenching phase. The unknown proportion of dwarf-like to primordial-like UDGs leaves the enigma of the nature of UDGs still open.

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arXiv2018

The Stellar Populations of Two Ultra-Diffuse Galaxies from Optical and Near-infrared Photometry

We present observational constraints on the stellar populations of two ultra-diffuse galaxies (UDGs) using optical through near-infrared (NIR) spectral energy distribution (SED) fitting. Our analysis is enabled by new $Spitzer$-IRAC 3.6 $μ$m and 4.5 $μ$m imaging, archival optical imaging, and the prospector fully Bayesian SED fitting framework. Our sample contains one field UDG (DGSAT I), one Virgo cluster UDG (VCC 1287), and one Virgo cluster dwarf elliptical for comparison (VCC 1122). We find that the optical--NIR colors of the three galaxies are significantly different from each other. We infer that VCC 1287 has an old ($\gtrsim7.7$ Gyr) and surprisingly metal-poor ($[Z/Z_{\odot}]\lesssim-1.0$) stellar population, even after marginalizing over uncertainties on diffuse interstellar dust. In contrast, the field UDG DGSAT I shows evidence of being younger than the Virgo UDG, with an extended star formation history and an age posterior extending down to $\sim3$ Gyr. The stellar metallicity of DGSAT I is sub-solar but higher than that of the Virgo UDG, with $[Z/Z_{\odot}]=-0.63^{+0.35}_{-0.62}$; in the case of exactly zero diffuse interstellar dust, DGSAT I may even have solar metallicity. With VCC 1287 and several Coma UDGs, a general picture is emerging where cluster UDGs may be "failed" galaxies, but the field UDG DGSAT I seems more consistent with a stellar feedback-induced expansion scenario. In the future, our approach can be applied to a large and diverse sample of UDGs down to faint surface brightness limits, with the goal of constraining their stellar ages, stellar metallicities, and circumstellar and diffuse interstellar dust content.

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arXiv2018

Exploring the limits of AGN feedback: black holes and the star formation histories of low-mass galaxies

Energy feedback, either from active galactic nuclei (AGN) or from supernovae, is required to understand galaxy formation within a $Λ$-Cold Dark Matter cosmology. We study a sample of 127 low-mass galaxies, comparing their stellar populations properties to the mass of the central supermassive black hole, in order to investigate the effect of AGN feedback. We find a loose coupling between star formation history and black hole mass, which seems to suggest that AGN activity does not dominate baryonic cooling in low-mass galaxies. We also find that a break in the $M_\bullet$-$σ$ relation marks a transitional stellar mass, M$_\mathrm{trans}=3.4\pm2.1 \times 10^{10}$ M$_{\odot}$, remarkably similar to M$_\star$. Our results are in agreement with a bi-modal star formation process where the AGN-dominated feedback of high-mass galaxies transitions towards a supernovae-driven regime in low-mass systems, as suggested by numerical simulations.

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arXiv2018

Timing the formation and assembly of early-type galaxies via spatially resolved stellar populations analysis

To investigate star formation and assembly processes of massive galaxies, we present here a spatially-resolved stellar populations analysis of a sample of 45 elliptical galaxies (Es) selected from the CALIFA survey. We find rather flat age and [Mg/Fe] radial gradients, weakly dependent on the effective velocity dispersion of the galaxy within half-light radius. However, our analysis shows that metallicity gradients become steeper with increasing galaxy velocity dispersion. In addition, we have homogeneously compared the stellar populations gradients of our sample of Es to a sample of nearby relic galaxies, i.e., local remnants of the high-z population of red nuggets. This comparison indicates that, first, the cores of present-day massive galaxies were likely formed in gas-rich, rapid star formation events at high redshift (z>2). This led to radial metallicity variations steeper than observed in the local Universe, and positive [Mg/Fe] gradients. Second, our analysis also suggests that a later sequence of minor dry mergers, populating the outskirts of early-type galaxies (ETGs), flattened the pristine [Mg/Fe] and metallicity gradients. Finally, we find a tight age-[Mg/Fe] relation, supporting that the duration of the star formation is the main driver of the [Mg/Fe] enhancement in massive ETGs. However, the star formation time-scale alone is not able to fully explain our [Mg/Fe] measurements. Interestingly, our results match the expected effect that a variable stellar initial mass function would have on the [Mg/Fe] ratio.

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arXiv2018

Black-hole-regulated star formation in massive galaxies

Super-massive black holes, with masses larger than a million times that of the Sun, appear to inhabit the centers of all massive galaxies. Cosmologically-motivated theories of galaxy formation need feedback from these super-massive black holes to regulate star formation. In the absence of such feedback, state-of-the-art numerical simulations dramatically fail to reproduce the number density and properties of massive galaxies in the local Universe. However, there is no observational evidence of this strongly coupled co-evolution between super-massive black holes and star formation, impeding our understanding of baryonic processes within galaxies. Here we show that the star formation histories (SFHs) of nearby massive galaxies, as measured from their integrated optical spectra, depend on the mass of the central super-massive black hole. Our results suggest that black hole mass growth scales with gas cooling rate in the early Universe. The subsequent quenching of star formation takes place earlier and more efficiently in galaxies hosting more massive central black holes. The observed relation between black hole mass and star formation efficiency applies to all generations of stars formed throughout a galaxy's life, revealing a continuous interplay between black hole activity and baryon cooling.

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