Impact of an AGN featureless continuum on estimation of stellar population properties

Cardoso, Leandro S. M.; Gomes, J. M.; Papaderos, P.

doi:10.1051/0004-6361/201630378

Cited by 24 publications

(20 citation statements)

References 98 publications

(146 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1). In terms of standard SFH parametrizations, the superposition of these processes might be empirically approximated by "delayed" exponentially declining SFR models (e.g., Cardoso et al 2017) with an e-folding timescale and a delay of the SFR peak scaling inversely to the present-day M ,T . We note that the evidence from this study is qualitatively consistent with insights gained from Lick index studies by, for example, Thomas & Davies (2006), which indicate that the smallest bulges show the lowest lightweighted ages and a late enrichment in iron from SNe Ia.…”

Section: The Continuous Rise Of Bulges Out Of Galactic Disksmentioning

confidence: 99%

The continuous rise of bulges out of galactic disks

Breda

Papaderos

2018

A&A

Self Cite

View full text Add to dashboard Cite

Context. A key subject in extragalactic astronomy concerns the chronology and driving mechanisms of bulge formation in late-type galaxies (LTGs). The standard scenario distinguishes between classical bulges and pseudo-bulges (CBs and PBs, respectively), the first thought to form monolithically prior to disks and the second gradually out of disks. These two bulge formation routes obviously yield antipodal predictions on the bulge age and bulge-to-disk age contrast, both expected to be high (low) in CBs (PBs). Aims. Our main goal is to explore whether bulges in present-day LTGs segregate into two evolutionary distinct classes, as expected from the standard scenario. Other questions motivating this study center on evolutionary relations between LTG bulges and their hosting disks, and the occurrence of accretion-powered nuclear activity as a function of bulge stellar mass M and stellar surface density Σ . Methods. In this study we have combined three techniques -surface photometry, spectral modeling of integral field spectroscopy data and suppression of stellar populations younger than an adjustable age cutoff with the code REMOVEYOUNG (RY) -toward a systematic analysis of the physical and evolutionary properties (e.g., M , Σ and mass-weighted stellar age t M and metallicity Z M , respectively) of a representative sample of 135 nearby (≤130 Mpc) LTGs from the CALIFA survey that cover a range between 10 8.9 M and 10 11.5 M in total stellar mass M ,T . In particular, the analysis here revolves around <δµ 9G >, a new distance-and formally extinction-independent measure of the contribution by stellar populations of age ≥9 Gyr to the mean r-band surface brightness of the bulge. We argue that <δµ 9G > offers a handy semi-empirical tracer of the physical and evolutionary properties of LTG bulges and a promising means for their characterization. Results. The essential insight from this study is that LTG bulges form over three dex in M and more than one dex in Σ a tight continuous sequence of increasing <δµ 9G > with increasing M , Σ , t M and Z M . Along this continuum of physical and evolutionary properties, our sample spans a range of ∼4 mag in <δµ 9G >: high-<δµ 9G > bulges are the oldest, densest and most massive ones ( t M ∼11.7 Gyr, Σ > 10 9 M kpc −2 , M ≥ 10 10 M ), whereas the opposite is the case for low-<δµ 9G > bulges ( t M ∼7 Gyr) that generally reside in low-mass LTGs. Furthermore, we find that the bulge-to-disk age and metallicity contrast, as well as the bulge-todisk mass ratio, show a positive trend with M ,T , raising from, respectively, ∼0 Gyr, ∼0 dex and 0.25 to ∼3 Gyr, ∼0.3 dex and 0.67 across the mass range covered by our sample. Whereas gas excitation in lower-mass ( 10 9.7 M ) bulges is invariably dominated by star formation (SF), LINER-and Seyfert-specific emission-line ratios were exclusively documented in high-mass ( 10 10 M ), high-Σ ( 10 9 M kpc −2 ) bulges. This is in agreement with previous work and consistent with the notion that the Eddington ratio or the black hole-to-bulge mass rati...

show abstract

Section: The Continuous Rise Of Bulges Out Of Galactic Disksmentioning

confidence: 99%

The continuous rise of bulges out of galactic disks

Breda

Papaderos

2018

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…As shown in Figures 7 and 8 in Cardoso et al (2017), the neglect of the AGN FC will cause an overestimation of ∼0.05−0.3 dex (depending on the shape of the FC) for the light-weighted stellar age when log t ⋆ L = 7, and an underestimation of ∼0.4 − 0.6 dex when log t ⋆ L = 10, for an intrinsic x AGN = 0.2. For log t ⋆ M , it will lead to an overestimation of 0.1 − 0.5 dex when log t ⋆ M = 9 to <0.1 dex when log t ⋆ M = 10.…”

Section: Effect Of An Agn Fc On the Derived Sfhsmentioning

confidence: 91%

“…However, these galaxies should have AGN contributions to the optical continuum though it could be intrinsically small. To have a rough estimation on how this biases our mean stellar age, we assume that we did not include an AGN FC in the input library, and then compare our results with those from Cardoso et al (2017), who have quantitatively examined the effect of an AGN FC on the estimation of SFHs of galaxies.…”

Section: Effect Of An Agn Fc On the Derived Sfhsmentioning

confidence: 99%

Stellar Populations of a Sample of Optically Selected AGN-host Dwarf Galaxies

Cai,

Zhao,

Zhang

et al. 2020

Preprint

View full text Add to dashboard Cite

In this paper we present our studies on the stellar populations and star formation histories (SFHs) for the Reines et al. sample of 136 dwarf galaxies which host active galactic nuclei (AGNs), selected from the Sloan Digital Sky Survey Data Release 8. We derive stellar populations and reconstruct SFHs for these AGN-host dwarfs using the stellar population synthesis code STARLIGHT. Our results suggest that these AGN-host dwarfs have assembled their stellar masses within a narrow period of time with the stellar mass-weighted ages in the range of 10 9 − 10 10 yr, but show a wide diversity of SFHs with the luminosity-weighted stellar ages in the range of 10 7 − 10 10 yr. The old population (t > 10 9 yr) contributes most to the galaxy light for the majority of the sample; the young population (t < 10 8 yr) also appears in significant but widely varying fractions, while the intermediate-age population (10 8 < t < 10 9 yr) in general contributes less to the optical continuum at 4020 Å. We also find that these dwarfs follow a similar mass-metallicity relation to normal star-forming galaxies, indicating that AGNs have little effect on the chemical evolution of the host galaxy. We further investigate the relation between the derived SFHs and morphology of the host galaxy, and find no correlation. Comparing the SFHs with the luminosity of the [O iii] λ5007 line (L [O iii] ), we find that there exists a mild correlation when L [O iii] > 10 39 erg s −1 , indicating that there is a physical connection between star formation and AGN activities in these dwarf galaxies.

show abstract

“…This allows the investigation of galaxies with complex SFHs: sudden bursts due to a merger, active galactic nuclei (AGNs) triggering, or the abrupt decline of star formation due to ram pressure stripping (e.g. Cardoso et al 2017;Pappalardo et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Self-consistent population spectral synthesis with FADO: II. Star formation history of galaxies in spectral synthesis methods

Pappalardo,

Cardoso,

Gomes

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Context. The field of galaxy evolution will make a great leap forward in the next decade as a consequence of the huge effort by the scientific community in multi-object spectroscopic facilities. Various future surveys will enormously increase the number of available galaxy spectra, providing new insights into unexplored areas of research. To maximise the impact of such incoming data, the analysis methods must also step up, extracting reliable information from the available spectra. It is therefore urgent to refine and test reliable analysis tools that are able to infer the properties of a galaxy from medium-or high-resolution spectra. Aims. In this paper we aim to investigate the limits and the reliability of different spectral synthesis methods in the estimation of the mean stellar age and metallicity. These two quantities are fundamental to determine the assembly history of a galaxy by providing key insights into its star formation history. The main question this work aims to address is which signal-to-noise ratios (S/N) are needed to reliably determine the mean stellar age and metallicity from a galaxy spectrum and how this depends on the tool used to model the spectra. Methods. To address this question we built a set of realistic simulated spectra containing stellar and nebular emission, reproducing the evolution of a galaxy in two limiting cases: a constant star formation rate and an exponentially declining star formation with a single initial burst. We degraded the synthetic spectra built from these two star formation histories (SFHs) to different S/N and analysed with three widely used spectral synthesis codes, namely Fado, Steckmap, and Starlight, assuming similar fitting set-ups and the same base of spectral templates. Results. For S/N ≤ 5 all the three tools show a large diversity in the results. The Fado and Starlight tools find median differences in the light-weighted mean stellar age of ∼0.1 dex, while Steckmap shows a higher value of ∼0.2 dex. For S/N > 50 the median differences in Fado are ∼0.03 dex (∼ 7%), a factor 3 and 4 lower than the 0.08 dex (∼20%) and 0.11 dex (∼30%) obtained from Starlight and Steckmap, respectively. Detailed investigations of the best-fit spectrum for galaxies with overestimated mass-weighted quantities point towards the inability of purely stellar models to fit the observed spectral energy distribution around the Balmer jump. Conclusions. Our results imply that when a galaxy enters a phase of high specific star formation rate (sSFR) the neglect of the nebular continuum emission in the fitting process has a strong impact on the estimation of its SFH when purely stellar fitting codes are used, even in presence of high S/N spectra. The median value of these differences are of the order of 7% (Fado), 20% (Starlight), and 30% (Steckmap) for light-weighted quantities, and 20% (Fado), 60% (Starlight), and 20% (Steckmap) for mass-weighted quantities. More specifically, for a continuous SFH both Steckmap and Starlight overestimate the stellar age by >2 dex within the first ∼100 My...

show abstract

Impact of an AGN featureless continuum on estimation of stellar population properties

Cited by 24 publications

References 98 publications

The continuous rise of bulges out of galactic disks

The continuous rise of bulges out of galactic disks

Stellar Populations of a Sample of Optically Selected AGN-host Dwarf Galaxies

Self-consistent population spectral synthesis with FADO: II. Star formation history of galaxies in spectral synthesis methods

Contact Info

Product

Resources

About