scholarly journals Early galaxy growth: mergers or gravitational instability?

2020 ◽  
Vol 500 (1) ◽  
pp. 118-137
Author(s):  
A Zanella ◽  
A Pallottini ◽  
A Ferrara ◽  
S Gallerani ◽  
S Carniani ◽  
...  
Keyword(s):  
Gravitational Instability ◽  
Far Infrared ◽  
Joint Effect ◽  
Data Sets ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
James Webb Space Telescope ◽  
The Galaxy ◽  
Hydrodynamical Simulations

ABSTRACT We investigate the spatially resolved morphology of galaxies in the early Universe. We consider a typical redshift z = 6 Lyman break galaxy, ‘Althæa’, from the SERRA hydrodynamical simulations. We create mock rest-frame ultraviolet (UV), optical, and far-infrared observations, and perform a two-dimensional morphological analysis to deblend the galaxy disc from substructures (merging satellites or star-forming regions). We find that the [C ii]158 μm emitting region has an effective radius 1.5–2.5 times larger than the optical one, consistent with recent observations. This [C ii] halo in our simulated galaxy arises as the joint effect of stellar outflows and carbon photoionization by the galaxy UV field, rather than from the emission of unresolved nearby satellites. At the typical angular resolution of current observations (≳ 0.15 arcsec) only merging satellites can be detected; detection of star-forming regions requires resolutions of ≲ 0.05 arcsec. The [C ii]-detected satellite has a 2.5-kpc projected distance from the galaxy disc, whereas the star-forming regions are embedded in the disc itself (distance ≲ 1 kpc). This suggests that multicomponent systems reported in the literature, which have separations ≳ 2 kpc, are merging satellites, rather than galactic substructures. Finally, the star-forming regions found in our mock maps follow the local L[C ii]–SFRUV relation of galaxy discs, although sampling the low-luminosity, low-SFR tail of the distribution. We show that future James Webb Space Telescope observations, bridging UV and [C ii] data sets, will be exceptionally suited to characterize galaxy substructures, thanks to their exquisite spatial resolution and sensitivity to both low-metallicity and dust-obscured regions that are bright at infrared wavelengths.

scholarly journals Photometric properties of reionization-epoch galaxies in the Simba simulations

2020 ◽  
Author(s):  
Xiaohan Wu ◽  
Romeel Davé ◽  
Sandro Tacchella ◽  
Jennifer Lotz
Keyword(s):  
Gas Phase ◽  
Luminosity Function ◽  
Line Of Sight ◽  
Star Forming ◽  
Dust Extinction ◽  
Star Forming Regions ◽  
James Webb Space Telescope ◽  
Hydrodynamical Simulations ◽  
Color Gradients ◽  
Attenuation Laws

Abstract We study the photometric properties and sizes of the reionization-epoch galaxies in high-resolution Simba cosmological hydrodynamical simulations with box sizes of [25, 50]h−1Mpc. Assuming various attenuation laws, we compute photometry by extincting each star particle’s spectrum using the line-of-sight gas metal column density. The predicted ultraviolet luminosity function (UVLF) generally agrees with observations at z = 6, owing to a partial cancellation between the high metallicities of the simulated galaxies and lower dust-to-metal ratios. The simulated z = 8 UVLF is low compared to observations, likely owing to excessive dust extinction. Simba predicts UV continuum slopes (β) in agreement with the z = 6 observations, with the best agreement obtained using a Calzetti extinction law. Interestingly, the gas-phase mass-metallicity relation in Simba is higher at z ∼ 6 than at z ∼ 2, suggesting that rapid early enrichment (and dust growth) might be necessary to match the observed β. We find that β is more sensitive to the dust extinction law than the UVLF. By generating mock James Webb Space Telescope (JWST) images and analysing in a manner similar to observations, we show that Simba’s galaxy size–luminosity relation well reproduces the current z = 6 Hubble observations. Unlike observations at lower redshifts, Simba predicts similar rest-UV and rest-optical sizes of z = 6 galaxies, owing to weak age gradients and dust extinction in star-forming regions counteract each other to weaken the color gradients within galaxies. These predictions will be testable with JWST.

scholarly journals The beauty of resolution: The SN Ib factory NGC 2770 spatially resolved

2014 ◽  
Vol 10 (S309) ◽  
pp. 169-170
Author(s):  
C. C. Thöne ◽  
L. Christensen ◽  
J. Gorosabel ◽  
A. de Ugarte Postigo
Keyword(s):  
Stellar Population ◽  
Late Type ◽  
Spiral Arms ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
The Galaxy ◽  
History Of ◽  
First Time

AbstractThe late-type spiral NGC 2770 hosted 3 Type Ib supernovae (SNe) in or next to star-forming regions in its outer spiral arms. We study the properties of the SN sites and the galaxy at different spatial resolutions to infer propeties of the SN progenitors and the SF history of the galaxy. Several 3D techniques are used and, for the first time, we present images of metallicity, shocks and stellar population ages from OSIRIS/GTC imaging with tunable narrowband filters.

scholarly journals The EDGE–CALIFA survey: using optical extinction to probe the spatially resolved distribution of gas in nearby galaxies

2019 ◽  
Vol 492 (2) ◽  
pp. 2651-2662 ◽  
Author(s):  
Jorge K Barrera-Ballesteros ◽  
Dyas Utomo ◽  
Alberto D Bolatto ◽  
Sebastián F Sánchez ◽  
Stuart N Vogel ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Spatial Scales ◽  
Empirical Relation ◽  
Data Sets ◽  
Optical Extinction ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
Nearby Galaxies ◽  
Cold Gas

ABSTRACT We present an empirical relation between the cold gas surface density (Σgas) and the optical extinction (AV) in a sample of 103 galaxies from the Extragalactic Database for Galaxy Evolution (EDGE) survey. This survey provides CARMA interferometric CO observations for 126 galaxies included in the Calar Alto Legacy Integral Field Area (CALIFA) survey. The matched, spatially resolved nature of these data sets allows us to derive the Σgas–AV relation on global, radial, and kpc (spaxel) scales. We determine AV from the Balmer decrement (H α/H β). We find that the best fit for this relation is $\Sigma _{\rm gas}\,(\rm {M_\odot \,pc}^{-2}) \sim 26 \times {\rm \mathit{ A}_\mathit{ V}} \,(\rm mag)$, and that it does not depend on the spatial scale used for the fit. However, the scatter in the fits increases as we probe smaller spatial scales, reflecting the complex relative spatial distributions of stars, gas, and dust. We investigate the Σgas/AV ratio on radial and spaxel scales as a function of $\mathrm{EW(H\,\alpha)}$. We find that at larger values of $\mathrm{EW({H\,\alpha })}$ (i.e. actively star-forming regions) this ratio tends to converge to twice the value expected for a foreground dust screen geometry (∼30 $\mathrm{M_{\odot } \, pc^{-2} \, mag^{-1}}$). On radial scales, we do not find a significant relation between the Σgas/AV ratio and the ionized gas metallicity. We contrast our estimates of Σgas using AV with compilations in the literature of the gas fraction on global and radial scales as well as with well-known scaling relations such as the radial star formation law and the Σgas–Σ* relation. These tests show that optical extinction is a reliable proxy for estimating Σgas in the absence of direct sub/millimeter observations of the cold gas.

scholarly journals Metallicity gradients of galaxies in the Herschel Reference Survey

2014 ◽  
Vol 10 (S309) ◽  
pp. 320-320
Author(s):  
Thomas M. Hughes
Keyword(s):  
Far Infrared ◽  
Pilot Project ◽  
Strong Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Very Large Telescope ◽  
Photometric Observations ◽  
The Galaxy ◽  
Nearby Galaxies ◽  
Cold Dust

AbstractWe introduce a pilot project to measure metallicitiy gradients for a sample of twenty nearby galaxies drawn from the Herschel Reference Survey (HRS), representative of normal, star-forming spiral galaxies. We have obtained optical spectroscopic observations using the Very Large Telescope with the FORS2 instrument in multi-object mode, targeting individual Hii and star-forming regions across the galaxy discs (P. I.: L. Cortese). From the ratios of the strong emission lines, we estimate the local gas-phase oxygen abundance and construct metallicity gradients. Combining these new data with Herschel PACS/SPIRE far-infrared photometric observations and Hi 21 cm line maps, to trace the cold dust and gas respectively, will allow the study of the relationships between stars, gas, dust and metals on sub-kiloparsec scales.

scholarly journals PÉGASE.3: A code for modeling the UV-to-IR/submm spectral and chemical evolution of galaxies with dust

2019 ◽  
Vol 623 ◽  
pp. A143 ◽  
Author(s):  
Michel Fioc ◽  
Brigitte Rocca-Volmerange
Keyword(s):  
Near Infrared ◽  
Far Infrared ◽  
Spectral Energy ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Galaxy ◽  
History Of ◽  
Mass Assembly ◽  
Individual Grains ◽  
The Masses

A code computing consistently the evolution of stars, gas and dust, as well as the energy they radiate, is required to derive reliably the history of galaxies by fitting synthetic spectral energy distributions (SEDs) to multiwavelength observations. The new code PÉGASE.3 described in this paper extends to the far-infrared/submillimeter the ultraviolet-to-near-infrared modeling provided by previous versions of PÉGASE. It first computes the properties of single stellar populations at various metallicities. It then follows the evolution of the stellar light of a galaxy and the abundances of the main metals in the interstellar medium (ISM), assuming some scenario of mass assembly and star formation. It simultaneously calculates the masses of the various grain families, the optical depth of the galaxy and the attenuation of the SED through the diffuse ISM in spiral and spheroidal galaxies, using grids of radiative transfer precomputed with Monte Carlo simulations taking scattering into account. The code determines the mean radiation field and the temperature probability distribution of stochastically heated individual grains. It then sums up their spectra to yield the overall emission by dust in the diffuse ISM. The nebular emission of the galaxy is also computed, and a simple modeling of the effects of dust on the SED of star-forming regions is implemented. The main outputs are ultraviolet-to-submillimeter SEDs of galaxies from their birth up to 20 Gyr, colors, masses of galactic components, ISM abundances of metallic elements and dust species, supernova rates. The temperatures and spectra of individual grains are also available. The paper discusses several of these outputs for a scenario representative of Milky Way-like spirals. PÉGASE.3 is fully documented and its Fortran 95 source files are public. The code should be especially useful for cosmological simulations and to interpret future mid- and far-infrared data, whether obtained by JWST, LSST, Euclid or e-ELT.

scholarly journals What drives galaxy quenching? Resolving molecular gas and star formation in the green valley

2020 ◽  
Vol 498 (1) ◽  
pp. L66-L71 ◽  
Author(s):  
Simcha Brownson ◽  
Francesco Belfiore ◽  
Roberto Maiolino ◽  
Lihwai Lin ◽  
Stefano Carniani
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Gas Content ◽  
Molecular Gas ◽  
Data Sets ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
Central Regions

ABSTRACT We study quenching in seven green valley galaxies on kpc scales by resolving their molecular gas content using 12CO(1–0) observations obtained with NOrthern Extended Millimeter Array and Atacama Large Millimeter Array, and their star formation rate using spatially resolved optical spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory survey. We perform radial stacking of both data sets to increase the sensitivity to molecular gas and star formation, thereby avoiding biases against strongly quenched regions. We find that both spatially resolved gas fraction (fgas) and star formation efficiency ($\rm {SFE}$) are responsible for quenching green valley galaxies at all radii: both quantities are suppressed with respect to typical star-forming regions. fgas and $\rm {SFE}$ have roughly equal influence in quenching the outer disc. We are, however, unable to identify the dominant mechanism in the strongly quenched central regions. We find that fgas is reduced by $\rm \sim\! 1~dex$ in the central regions, but the star formation rate is too low to be measured, leading to upper limits for the $\rm {SFE}$. Moving from the outer disc to central regions, the reduction in fgas is driven by an increasing $\rm \Sigma _{\star }$ profile rather than a decreasing $\rm \Sigma _{H_{2}}$ profile. The reduced fgas may therefore be caused by a decrease in the gas supply rather than molecular gas ejection mechanisms, such as winds driven by active galactic nuclei. We warn more generally that studies investigating fgas may be deceiving in inferring the cause of quenching, particularly in the central (bulge-dominated) regions of galaxies.

scholarly journals Self-Gravitational Instability of an Isothermal Gaseous Slab under High External Pressure

2001 ◽  
Vol 205 ◽  
pp. 286-287
Author(s):  
Michihisa Umekawa ◽  
Ryoji Matsumoto ◽  
Shigeki Miyaji ◽  
Tatsuo Yoshida
Keyword(s):  
Star Formation ◽  
Galactic Center ◽  
Gravitational Instability ◽  
Three Dimensional ◽  
External Pressure ◽  
Star Forming ◽  
Star Forming Regions ◽  
Field Lines ◽  
Hydrodynamical Simulations ◽  
The Magnetic Field

In active massive star forming regions such as Orion and the Galactic center, the self-gravitational instability of a magnetized gaseous slab plays an important role as a trigger of star formation. In such high external pressure regions, the incompressible mode of self-gravitational instability (Elmegreen & Elmegreen 1978; Lubow & Pringle 1992) becomes dominant. Based on two-dimensional hydrodynamical simulations, Umekawa et al. (1999) proposed “Star formation by merging of the Jeans stable clumps” in a pressure bounded slab. In a magnetized slab confined by external pressure, Nagai et al. (1998) showed by linear analysis that the slab fragments to filaments parallel to the magnetic field lines. Here, we show by nonlinear three-dimensional MHD simulations that the filaments further fragment to Jeans stable clumps.

scholarly journals Resolving distant, dusty galaxies using observations and simulations

2019 ◽  
Vol 15 (S352) ◽  
pp. 282-286
Author(s):  
R. K. Cochrane
Keyword(s):  
Rest Frame ◽  
High Redshift ◽  
Far Infrared ◽  
Small Sample ◽  
Star Forming ◽  
Spatially Resolved ◽  
Dusty Galaxies ◽  
Wavelength Emission ◽  
Hydrodynamical Simulations ◽  
Far Ultraviolet

AbstractSpatially resolved studies of galaxies in the high-redshift Universe have traditionally been reliant on data at rest-frame optical and UV wavelengths, which can be biased towards the least dust-obscured galaxies. For several years now, we have been able to resolve and probe the morphology of longer-wavelength emission from distant galaxies with ALMA, and a number of recent ALMA studies were presented at the IAU Symposium No. 352. These included our study of the resolved multi-wavelength emission of galaxies at z ∼ 2. As part of the SHiZELS collaboration, we are mapping the Hα emission line (from SINFONI/VLT), UV continuum (from HST), and the far-infrared (from ALMA) emission from a small sample of Hα-selected galaxies. In this proceedings paper, we showcase the high quality of our data, and the spectacular structures displayed by one of our most dusty sources. We also provide an overview of some highly complementary simulation-based work, using galaxies drawn from the FIRE-2 zoom-in cosmological hydrodynamical simulations. Using sophisticated radiative transfer techniques, we have derived predictions for the spatially-resolved emission of a sample of star-forming galaxies, from rest-frame far-ultraviolet to the far-infrared. For both observed and simulated galaxies, emission maps show striking differences with wavelength, with the same galaxy appearing clumpy and extended in the far-ultraviolet yet compact at far-infrared wavelengths.

scholarly journals Reproducing the Universe: a comparison between the EAGLE simulations and the nearby DustPedia galaxy sample

2020 ◽  
Vol 494 (2) ◽  
pp. 2823-2838 ◽  
Author(s):  
Ana Trčka ◽  
Maarten Baes ◽  
Peter Camps ◽  
Sharon E Meidt ◽  
James Trayford ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Physical Properties ◽  
Numerical Models ◽  
Far Infrared ◽  
Spectral Energy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Global Emission ◽  
Galaxy Sample ◽  
Galaxy Population

ABSTRACT We compare the spectral energy distributions (SEDs) and inferred physical properties for simulated and observed galaxies at low redshift. We exploit UV-submillimetre mock fluxes of ∼7000 z = 0 galaxies from the EAGLE suite of cosmological simulations, derived using the radiative transfer code skirt. We compare these to ∼800 observed galaxies in the UV-submillimetre range, from the DustPedia sample of nearby galaxies. To derive global properties, we apply the SED fitting code cigale consistently to both data sets, using the same set of ∼80 million models. The results of this comparison reveal overall agreement between the simulations and observations, both in the SEDs and in the derived physical properties, with a number of discrepancies. The optical and far-infrared regimes, and the scaling relations based upon the global emission, diffuse dust, and stellar mass, show high levels of agreement. However, the mid-infrared fluxes of the EAGLE galaxies are overestimated while the far-UV domain is not attenuated enough, compared to the observations. We attribute these discrepancies to a combination of galaxy population differences between the samples and limitations in the subgrid treatment of star-forming regions in the EAGLE-skirt post-processing recipe. Our findings show the importance of detailed radiative transfer calculations and consistent comparison, and provide suggestions for improved numerical models.

scholarly journals Using stellar population studies to determine the progenitors of GRBs and SNe

2009 ◽  
Vol 5 (S262) ◽  
pp. 436-437
Author(s):  
Christina C. Thöne ◽  
Lise Christensen ◽  
Johan P. U. Fynbo
Keyword(s):  
Emission Line ◽  
Stellar Population ◽  
Population Studies ◽  
Population Models ◽  
Host Galaxy ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions

AbstractWe present spatially resolved emission line studies of three nearby GRB and SN hosts with longslit and/or IFU observations. We compare the environment of the GRBs/SNe with those of other star-forming regions in the host galaxy and try to get informations on the progenitor from stellar population models and metallicities.

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