Self-consistent population spectral synthesis with FADO

Context. Spectral population synthesis (PS) is a fundamental tool in extragalactic research that aims to decipher the assembly history of galaxies from their spectral energy distribution (SED). Whereas this technique has led to key insights into galaxy evolution in recent decades, star formation histories (SFHs) inferred therefrom have been plagued by considerable uncertainties stemming from inherent degeneracies and the fact that until recently all PS codes were restricted to purely stellar fits, neglecting the essential contribution of nebular emission (ne). With the advent of FADO (Fitting Analysis using Differential evolution Optimisation), the now possible self-consistent modelling of stellar and ne opens new routes to the exploration of galaxy SFHs. Aims. The main goal of this study is to quantitatively explore the accuracy to which FADO can recover physical and evolutionary properties of galaxies and compare its output with that from purely stellar PS codes. Methods. FADO and STARLIGHT were applied to synthetic SEDs that track the spectral evolution of stars and gas in extinction-free mock galaxies of solar metallicity that form their stellar mass (M⋆) according to different parametric SFHs. Spectral fits were computed for two different set-ups that approximate the spectral range of SDSS and CALIFA (V500) data, using up to seven libraries of simple stellar population spectra in the 0.005–2.5 Z⊙ metallicity range. Results. Our analysis indicates that FADO can recover the key physical and evolutionary properties of galaxies, such as M⋆ and mass- and light-weighted mean age and metallicity, with an accuracy better than 0.2 dex. This is the case even in phases of strongly elevated specific star formation rate (sSFR) and thus with considerable ne contamination (EW(Hα) > 103 Å). Likewise, population vectors from FADO adequately recover the mass fraction of stars younger than 10 Myr and older than 1 Gyr (M⋆<10Myr/M⋆total and M⋆>1Gyr/M⋆total, respectively) and reproduce with a high fidelity the observed Hα luminosity. As for STARLIGHT, our analysis documents a moderately good agreement with theoretical values only for evolutionary phases for which ne drops to low levels (EW(Hα) ≤ 60 Å) which, depending on the assumed SFH, correspond to an age between ∼0.1 Gyr and 2–4 Gyr. However, fits with STARLIGHT during phases of high sSFR severely overestimate both M⋆ and the mass-weighted stellar age, whereas strongly underestimate the light-weighted age and metallicity. Furthermore, our analysis suggests a subtle tendency of STARLIGHT to favour a bi-modal SFH, as well a slightly overestimated M⋆<10Myr/M⋆total, regardless of galaxy age. Whereas the amplitude of these biases can be reduced, depending on the specifics of the fitting procedure (e.g. accuracy and completeness of flagging emission lines, omission of the Balmer and Paschen jump from the fit), they persist even in the idealised case of a line-free SED comprising only stellar and nebular continuum emission. Conclusions. The insights from this study suggest that the neglect of nebular continuum emission in STARLIGHT and similar purely stellar PS codes could systematically impact M⋆ and SFH estimates for star-forming galaxies. We argue that these biases can be relevant in the study of a range of topics in extragalactic research, including the redshift-dependent slope of the star formation (SF) main sequence, the SF frosting hypothesis, and the regulatory role of supermassive black holes on the global SFH of galaxies.

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Fraction of bolometric luminosity absorbed by dust in DustPedia galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833699 ◽

2018 ◽

Vol 620 ◽

pp. A112 ◽

Cited By ~ 16

Author(s):

S. Bianchi ◽

P. De Vis ◽

S. Viaene ◽

A. Nersesian ◽

A. V. Mosenkov ◽

...

Keyword(s):

Star Formation ◽

Galaxy Evolution ◽

Star Formation Rate ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Spectral Energy ◽

Stellar Content ◽

Late Type ◽

Bolometric Luminosity ◽

Stellar Radiation

Aims. We aim to study the fraction of stellar radiation absorbed by dust, fabs, in 814 galaxies of different morphological types. The targets constitute the vast majority (93%) of the DustPedia sample, including almost all large (optical diameter larger than 1′), nearby (v ≤ 3000 km s−1) galaxies observed with the Herschel Space Observatory. Methods. For each object, we modelled the spectral energy distribution from the ultraviolet to the sub-millimetre using the dedicated, aperture-matched DustPedia photometry and the Code Investigating GALaxy Evolution (CIGALE). The value of fabs was obtained from the total luminosity emitted by dust and from the bolometric luminosity, which are estimated by the fit. Results. On average, 19% of the stellar radiation is absorbed by dust in DustPedia galaxies. The fraction rises to 25% if only late-type galaxies are considered. The dependence of fabs on morphology, showing a peak for Sb-Sc galaxies, is weak; it reflects a stronger, yet broad, positive correlation with the bolometric luminosity, which is identified for late-type, disk-dominated, high-specific-star-formation rate, gas-rich objects. We find no variation of fabs with inclination, at odds with radiative transfer models of edge-on galaxies. These results call for a self-consistent modelling of the evolution of the dust mass and geometry along the build-up of the stellar content. We also provide template spectral energy distributions in bins of morphology and luminosity and study the variation of fabs with stellar mass and specific star-formation rate. We confirm that the local Universe is missing the high fabs, luminous and actively star-forming objects necessary to explain the energy budget in observations of the extragalactic background light.

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AGN and Star Formation in HerMES-IRS sources

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314003305 ◽

2013 ◽

Vol 9 (S304) ◽

pp. 52-55

Author(s):

Anna Feltre ◽

Evanthia Hatziminaoglou ◽

Antonio Hernán-Caballero ◽

Jacopo Fritz ◽

Alberto Franceschini ◽

...

Keyword(s):

Star Formation ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Galactic Nuclei ◽

Spectral Energy ◽

Host Galaxies ◽

Fitting Procedure ◽

Multi Wavelength ◽

Dust Component ◽

The Impact

AbstractOne of the remaining open issues in the context of the analysis of Active Galactic Nuclei (AGN) is the evidence that nuclear gravitational accretion is often accompanied by a concurrent starburst activity. We developed a spectral energy distribution (SED) fitting technique to derive simultaneously the physical properties of active galaxies and coexisting starbursts making the best use of Spitzer and Herschel IR observations. We apply the SED fitting procedure to a large sample of extragalactic sources representing the HerMES (Herschel/Multi-tiered Extragalactic Survey) population with IRS spectra with a plethora of multi-wavelength data in order to study the impact of a possible presence of an AGN on the host galaxy's properties. We analyze the star formation rate (SFR) in conncetion to the presence of an AGN and compared the properties of the hot (AGN) and cold (starburst) dust component. Our findings are consistent with no evidence for the presence of an AGN affecting the star formation processes of the host galaxies.

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SMM J04135+10277: a distant QSO–starburst system caught by ALMA

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa472 ◽

2020 ◽

Vol 493 (3) ◽

pp. 3744-3756 ◽

Cited By ~ 1

Author(s):

Judit Fogasy ◽

K K Knudsen ◽

G Drouart ◽

C D P Lagos ◽

L Fan

Keyword(s):

Star Formation ◽

Galaxy Evolution ◽

Spectral Energy Distribution ◽

Line Emission ◽

Continuum Emission ◽

Host Galaxy ◽

Spectral Energy ◽

Molecular Gas ◽

Gas Reservoir ◽

Companion Galaxy

ABSTRACT The gas content of galaxies is a key factor for their growth, starting from star formation and black hole accretion to galaxy mergers. Thus, characterizing its properties through observations of tracers like the CO emission line is of big importance in order to understand the bigger picture of galaxy evolution. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of dust continuum, CO(5–4) and CO(8–7) line emission in the quasar–star-forming companion system SMM J04135+10277 (z = 2.84). Earlier low-J CO studies of this system found a huge molecular gas reservoir associated with the companion galaxy, while the quasar appeared gas-poor. Our CO observations revealed that the host galaxy of the quasar is also gas-rich, with an estimated molecular gas mass of $\sim (0.7{\!-\!}2.3)\times 10^{10}\, \rm M_{\odot}$. The CO line profiles of the companion galaxy are very broad ($\sim 1000\, \rm km\, s^{-1}$), and show signs of rotation of a compact, massive system. In contrast to previous far-infrared observations, we resolve the continuum emission and detect both sources, with the companion galaxy dominating the dust continuum and the quasar having a $\sim 25{{\ \rm per\ cent}}$ contribution to the total dust emission. By fitting the infrared spectral energy distribution of the sources with mr-moose and empirical templates, the infrared luminosities of the quasar and the companion are in the range of $L_{\rm IR, QSO}\sim (2.1{\!-\!}9.6)\times 10^{12}\, \rm L_{\odot}$ and $L_{\rm IR, Comp.}\sim (2.4{\!-\!}24)\times 10^{12}\, \rm L_{\odot}$, while the estimated star formation rates are $\sim 210{\!-\!}960$ and $\sim 240{\!-\!}2400\, \rm M_{\odot }\, yr^{-1}$, respectively. Our results demonstrate that non-detection of low-J CO transition lines in similar sources does not necessarily imply the absence of massive molecular gas reservoir but that the excitation conditions favour the excitation of high-J transitions.

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The effects of star formation history in the SFR–M* relation of H ii galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3333 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3240-3253

Author(s):

Amanda R Lopes ◽

Eduardo Telles ◽

Jorge Melnick

Keyword(s):

Star Formation ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Star Formation History ◽

Spectral Energy ◽

Distribution Fitting ◽

Good Tool ◽

Star Forming ◽

Additional Information ◽

Star Formation Histories

ABSTRACT We discuss the implications of assuming different star formation histories (SFH) in the relation between star formation rate (SFR) and mass derived by the spectral energy distribution fitting (SED). Our analysis focuses on a sample of H ii galaxies, dwarf starburst galaxies spectroscopically selected through their strong narrow emission lines in SDSS DR13 at z < 0.4, cross-matched with photometric catalogues from GALEX, SDSS, UKIDSS, and WISE. We modelled and fitted the SEDs with the code CIGALE adopting different descriptions of SFH. By adding information from different independent studies, we find that H ii galaxies are best described by episodic SFHs including an old (10 Gyr), an intermediate age (100−1000 Myr) and a recent population with ages < 10 Myr. H ii galaxies agree with the SFR−M* relation from local star-forming galaxies, and only lie above such relation when the current SFR is adopted as opposed to the average over the entire SFH. The SFR−M* demonstrated not to be a good tool to provide additional information about the SFH of H ii galaxies, as different SFH present a similar behaviour with a spread of <0.1 dex.

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Towards a census of high-redshift dusty galaxies with Herschel

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731888 ◽

2018 ◽

Vol 614 ◽

pp. A33 ◽

Cited By ~ 9

Author(s):

D. Donevski ◽

V. Buat ◽

F. Boone ◽

C. Pappalardo ◽

M. Bethermin ◽

...

Keyword(s):

Galaxy Evolution ◽

High Redshift ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Far Infrared ◽

Virgo Cluster ◽

Spectral Energy ◽

Distribution Fitting ◽

Redshift Distribution ◽

Star Forming

Context. Over the last decade a large number of dusty star-forming galaxies has been discovered up to redshift z = 2 − 3 and recent studies have attempted to push the highly confused Herschel SPIRE surveys beyond that distance. To search for z ≥ 4 galaxies they often consider the sources with fluxes rising from 250 μm to 500 μm (so-called “500 μm-risers”). Herschel surveys offer a unique opportunity to efficiently select a large number of these rare objects, and thus gain insight into the prodigious star-forming activity that takes place in the very distant Universe. Aims. We aim to implement a novel method to obtain a statistical sample of 500 μm-risers and fully evaluate our selection inspecting different models of galaxy evolution. Methods. We consider one of the largest and deepest Herschel surveys, the Herschel Virgo Cluster Survey. We develop a novel selection algorithm which links the source extraction and spectral energy distribution fitting. To fully quantify selection biases we make end-to-end simulations including clustering and lensing. Results. We select 133 500 μm-risers over 55 deg2, imposing the criteria: S500 > S350 > S250, S250 > 13.2 mJy and S500 > 30 mJy. Differential number counts are in fairly good agreement with models, displaying a better match than other existing samples. The estimated fraction of strongly lensed sources is 24+6-5% based on models. Conclusions. We present the faintest sample of 500 μm-risers down to S250 = 13.2 mJy. We show that noise and strong lensing have an important impact on measured counts and redshift distribution of selected sources. We estimate the flux-corrected star formation rate density at 4 < z < 5 with the 500 μm-risers and find it to be close to the total value measured in far-infrared. This indicates that colour selection is not a limiting effect to search for the most massive, dusty z > 4 sources.

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The star formation properties of the observed and simulated AGN Universe: BAT versus EAGLE

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2414 ◽

2020 ◽

Vol 498 (2) ◽

pp. 2323-2338

Author(s):

Thomas M Jackson ◽

D J Rosario ◽

D M Alexander ◽

J Scholtz ◽

Stuart McAlpine ◽

...

Keyword(s):

Star Formation ◽

High Redshift ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Host Galaxy ◽

Spectral Energy ◽

Host Galaxies ◽

X Ray ◽

Two Samples ◽

Stellar Masses

ABSTRACT In this paper, we present data from 72 low-redshift, hard X-ray selected active galactic nucleus (AGN) taken from the Swift–BAT 58 month catalogue. We utilize spectral energy distribution fitting to the optical to infrared photometry in order to estimate host galaxy properties. We compare this observational sample to a volume- and flux-matched sample of AGN from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulations in order to verify how accurately the simulations can reproduce observed AGN host galaxy properties. After correcting for the known +0.2 dex offset in the SFRs between EAGLE and previous observations, we find agreement in the star formation rate (SFR) and X-ray luminosity distributions; however, we find that the stellar masses in EAGLE are 0.2–0.4 dex greater than the observational sample, which consequently leads to lower specific star formation rates (sSFRs). We compare these results to our previous study at high redshift, finding agreement in both the observations and simulations, whereby the widths of sSFR distributions are similar (∼0.4–0.6 dex) and the median of the SFR distributions lie below the star-forming main sequence by ∼0.3–0.5 dex across all samples. We also use EAGLE to select a sample of AGN host galaxies at high and low redshift and follow their characteristic evolution from z = 8 to z = 0. We find similar behaviour between these two samples, whereby star formation is quenched when the black hole goes through its phase of most rapid growth. Utilizing EAGLE we find that 23 per cent of AGN selected at z ∼ 0 are also AGN at high redshift, and that their host galaxies are among the most massive objects in the simulation. Overall, we find EAGLE reproduces the observations well, with some minor inconsistencies (∼0.2 dex in stellar masses and ∼0.4 dex in sSFRs).

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Serendipitous discovery of an “ALMA-only” galaxy at 5 < z < 6 in an ALMA 3-mm survey

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320000605 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 194-198

Author(s):

Christina C. Williams

Keyword(s):

Star Formation ◽

Energy Distribution ◽

Star Formation Rate ◽

High Redshift ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Spectral Energy ◽

Large Contribution ◽

Massive Galaxies ◽

Multi Wavelength

AbstractWe discuss the serendipitous discovery of a dusty high-redshift galaxy in a small (8 arcmin2) ALMA 3-mm survey Williams et al. (2019). The galaxy was previously unknown and is absent from existing multi-wavelength catalogs (“ALMA-only”). Using the ALMA position as prior, we perform forced deblended photometry to constrain its spectral energy distribution. The spectral energy distribution is well described by a massive (M* = 1010.8 M⊙) and highly obscured (AV ∼ 4) galaxy at redshift z = 5.5 ± 1.1 with star formation rate ∼ 300 M⊙yr−1. Our small survey area implies an uncertain but large contribution to the cosmic star formation rate density, similar to the contribution from all ultraviolet-selected galaxies combined at this redshift. This galaxy likely traces an abundant population of massive galaxies absent from current samples of infrared-selected or sub-millimeter galaxies, but with larger space densities, higher duty cycles, and significant contribution to the cosmic star-formation rate and stellar mass densities.

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Spectral synthesis of stellar populations in the 3D era: The CALIFA experience

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314009387 ◽

2014 ◽

Vol 10 (S309) ◽

pp. 93-98

Author(s):

R. Cid Fernandes ◽

E. A. D. Lacerda ◽

R. M. González Delgado ◽

N. Vale Asari ◽

R. García-Benito ◽

...

Keyword(s):

Star Formation ◽

Galaxy Evolution ◽

Spectral Synthesis ◽

Mass Density ◽

Formation Rate ◽

Stellar Populations ◽

Data Cubes ◽

The Mean ◽

Stellar Masses ◽

Star Formation Histories

AbstractMethods to recover the fossil record of galaxy evolution encoded in their optical spectra have been instrumental in processing the avalanche of data from mega-surveys along the last decade, effectively transforming observed spectra onto a long and rich list of physical properties: from stellar masses and mean ages to full star formation histories. This promoted progress in our understanding of galaxies as a whole. Yet, the lack of spatial resolution introduces undesirable aperture effects, and hampers advances on the internal physics of galaxies. This is now changing with 3D surveys. The mapping of stellar populations in data-cubes allows us to figure what comes from where, unscrambling information previously available only in integrated form. This contribution uses our starlight-based analysis of 300 CALIFA galaxies to illustrate the power of spectral synthesis applied to data-cubes. The selected results highlighted here include: (a) The evolution of the mass-metallicity and mass-density-metallicity relations, as traced by the mean stellar metallicity. (b) A comparison of star formation rates obtained from Hα to those derived from full spectral fits. (c) The relation between star formation rate and dust optical depth within galaxies, which turns out to mimic the Schmidt-Kennicutt law. (d) PCA tomography experiments.

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Simulating JWST deep extragalactic imaging surveys and physical parameter recovery

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037450 ◽

2020 ◽

Vol 640 ◽

pp. A67

Author(s):

O. B. Kauffmann ◽

O. Le Fèvre ◽

O. Ilbert ◽

J. Chevallard ◽

C. C. Williams ◽

...

Keyword(s):

Star Formation ◽

Near Infrared ◽

High Redshift ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Spectral Energy ◽

Photometric Redshifts ◽

The Galaxy ◽

Stellar Masses ◽

The Impact

We present a new prospective analysis of deep multi-band imaging with the James Webb Space Telescope (JWST). In this work, we investigate the recovery of high-redshift 5 < z < 12 galaxies through extensive image simulations of accepted JWST programs, including the Early Release Science in the EGS field and the Guaranteed Time Observations in the HUDF. We introduced complete samples of ∼300 000 galaxies with stellar masses of log(M*/M⊙) > 6 and redshifts of 0 < z < 15, as well as galactic stars, into realistic mock NIRCam, MIRI, and HST images to properly describe the impact of source blending. We extracted the photometry of the detected sources, as in real images, and estimated the physical properties of galaxies through spectral energy distribution fitting. We find that the photometric redshifts are primarily limited by the availability of blue-band and near-infrared medium-band imaging. The stellar masses and star formation rates are recovered within 0.25 and 0.3 dex, respectively, for galaxies with accurate photometric redshifts. Brown dwarfs contaminating the z > 5 galaxy samples can be reduced to < 0.01 arcmin−2 with a limited impact on galaxy completeness. We investigate multiple high-redshift galaxy selection techniques and find that the best compromise between completeness and purity at 5 < z < 10 using the full redshift posterior probability distributions. In the EGS field, the galaxy completeness remains higher than 50% at magnitudes mUV < 27.5 and at all redshifts, and the purity is maintained above 80 and 60% at z ≤ 7 and 10, respectively. The faint-end slope of the galaxy UV luminosity function is recovered with a precision of 0.1–0.25, and the cosmic star formation rate density within 0.1 dex. We argue in favor of additional observing programs covering larger areas to better constrain the bright end.

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The brightest galaxies in the dark ages: Galaxies’ dust continuum emission out to the reionization era

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001350 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 349-349

Author(s):

Caitlin Casey

Keyword(s):

Star Formation ◽

Early Universe ◽

Luminosity Function ◽

Formation Rate ◽

Continuum Emission ◽

Spectral Energy ◽

Universe Model ◽

Star Forming ◽

Number Counts ◽

Galaxy Luminosity Function

AbstractThough half of cosmic starlight is absorbed by dust and reradiated at long wavelengths (3μ m – 3 mm), constraints on the infrared through millimeter galaxy luminosity function (the ‘IRLF’) are poor in comparison to the rest-frame ultraviolet and optical galaxy luminosity function, particularly at z ⩾ 2.5. Here we present a backward evolution model for interpreting number counts, redshift distributions, and cross-band flux density correlations in the infrared and submillimeter sky, from 70μm – 2 mm, using a model for the IRLF out to the epoch of reionization. Mock submillimeter maps are generated by injecting sources according to the prescribed IRLF and flux densities drawn from model spectral energy distributions that mirror the distribution of SEDs observed in 0 < z 0 < 5 dusty star-forming galaxies (DSFGs). We explore two extreme hypothetical case-studies: a dust-poor early Universe model, where DSFGs contribute negligibly (< 10%) to the integrated star-formation rate density at z > 4, and an alternate dust-rich early Universe model, where DSFGs dominate > 90% of z > 4 star-formation. We find that current submm/mm datasets do not clearly rule out either of these extreme models. We suggest that future surveys at 2 mm – both from ALMA and single-dish facilities – will be crucial to measuring the IRLF beyond z > 4.

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