scholarly journals Modelling the M*–SFR relation at high redshift: untangling factors driving biases in the intrinsic scatter measurement

2021 ◽  
Vol 503 (4) ◽  
pp. 4855-4877
Author(s):  
E Curtis-Lake ◽  
J Chevallard ◽  
S Charlot ◽  
L Sandles
Keyword(s):  
Star Formation ◽  
Time Scales ◽  
Main Sequence ◽  
Broad Band ◽  
Previous History ◽  
Point Sources ◽  
Emission Lines ◽  
Star Formation History ◽  
Medium Band ◽  
Intrinsic Scatter

ABSTRACT We present a method to self-consistently propagate stellar-mass [$\hbox{$\hbox{${\rm M}$}_{\star }$}=\log (\hbox{${\rm M}$}/\hbox{${\rm M}_{\odot }$})$] and star-formation-rate [$\hbox{${\Psi }$}=\log (\hbox{${\psi }$}/\hbox{${\rm M}_{\odot }$}\, {\rm yr}^{-1}$)] uncertainties on to intercept (α), slope (β), and intrinsic-scatter (σ) estimates for a simple model of the main sequence of star-forming galaxies, where $\hbox{${\Psi }$}= \alpha + \beta \hbox{$\hbox{${\rm M}$}_{\star }$}+ \mathcal {N}(0,\sigma)$. To test this method and compare it with other published methods, we construct mock photometric samples of galaxies at z ∼ 5 based on idealized models combined with broad- and medium-band filters at wavelengths 0.8–5 μm. Adopting simple Ψ estimates based on dust-corrected ultraviolet luminosity can underestimate σ. We find that broad-band fluxes alone cannot constrain the contribution from emission lines, implying that strong priors on the emission-line contribution are required if no medium-band constraints are available. Therefore, at high redshifts, where emission lines contribute a higher fraction of the broad-band flux, photometric fitting is sensitive to Ψ variations on short (∼10 Myr) time-scales. Priors on age imposed with a constant (or rising) star formation history (SFH) do not allow one to investigate a possible dependence of σ on $\hbox{${\rm M}$}_{\star }$ at high redshifts. Delayed exponential SFHs have less constrained priors, but do not account for Ψ variations on short time-scales, a problem if σ increases due to stochasticity of star formation. A simple SFH with current star formation decoupled from the previous history is appropriate. We show that, for simple exposure-time calculations assuming point sources, with low levels of dust, we should be able to obtain unbiased estimates of the main sequence down to $\mathrm{ log}(\hbox{${\rm M}$}/\hbox{${\rm M}_{\odot }$})\sim 8$ at z ∼ 5 with the James Webb Space Telescope while allowing for stochasticity of star formation.

scholarly journals Light element abundance inhomogeneities in globular clusters: probing star formation and evolution in the early Milky Way

1994 ◽  
Vol 72 (11-12) ◽  
pp. 772-781 ◽  
Author(s):  
Michael M. Briley ◽  
Roger A. Bell ◽  
James E. Hesser ◽  
Graeme H. Smith
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Main Sequence ◽  
Light Element ◽  
Star Formation History ◽  
Element Abundance ◽  
Chemical Compositions ◽  
Original Material ◽  
Abundance Patterns ◽  
Red Giant

Abundance patterns of the elements C, N, and O are sensitive probes of stellar nucleosynthesis processes and, in addition, O abundances are an important input for stellar age determinations. Understanding the nature of the observed distribution of these elements is key to constraining protogalactic star formation history. Patterns deduced from low-resolution spectroscopy of the CN, CH, NH, and CO molecules for low-mass stars in their core-hydrogen or first shell-hydrogen burning phases in the oldest ensembles known, the Galactic globular star clusters, are reviewed. New results for faint stars in NGC 104 (47 Tuc, C0021-723) reveal that the bimodal, anticorrelated pattern of CN and CH strengths found among luminous evolved stars is also present in stars nearing the end of their main-sequence lifetimes. In the absence of known mechanisms to mix newly synthesized elements from the interior to the observable surface layers of such unevolved stars, those particular inhomogeneities imply that the original material from which the stars formed some 15 billion years ago was chemically inhomogeneous in the C and N elements. However, in other clusters, observations of abundance ratios and C isotope ratios suggest that alterations to surface chemical compositions are produced as stars evolve from the main sequence through the red giant branch. Thus, the current observed distributions of C, N, and O among the brightest stars (those also observed most often) may not reflect the true distribution from which the protocluster cloud formed. The picture that is emerging of the C, N, and O abundance patterns within globular clusters may be one which requires a complicated combination of stellar evolutionary and primordial effects for its explanation.

scholarly journals Surrogate modelling the Baryonic Universe – I. The colour of star formation

2020 ◽  
Vol 495 (2) ◽  
pp. 2088-2104
Author(s):  
Jonás Chaves-Montero ◽  
Andrew Hearin
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Principal Component ◽  
Major Axis ◽  
Sloan Digital Sky Survey ◽  
Star Formation History ◽  
Spectral Energy ◽  
Colour Space

ABSTRACT The spectral energy distribution of a galaxy emerges from the complex interplay of many physical ingredients, including its star formation history (SFH), metallicity evolution, and dust properties. Using galaxpy, a new galaxy spectral prediction tool, and SFHs predicted by the empirical model universemachine and the cosmological hydrodynamical simulation IllustrisTNG, we isolate the influence of SFH on optical and near-infrared colours from 320 to 1080 Å at z = 0. By carrying out a principal component analysis, we show that physically motivated SFH variations modify galaxy colours along a single direction in colour space: the SFH-direction. We find that the projection of a galaxy’s present-day colours on to the SFH-direction is almost completely regulated by the fraction of stellar mass that the galaxy formed over the last billion years. Together with cosmic downsizing, this results in galaxies becoming redder as their host halo mass increases. We additionally study the change in galaxy colours due to variations in metallicity, dust attenuation, and nebular emission lines, finding that these properties vary broad-band colours along distinct directions in colour space relative to the SFH-direction. Finally, we show that the colours of low-redshift Sloan Digital Sky Survey galaxies span an ellipsoid with significant extent along two independent dimensions, and that the SFH-direction is well-aligned with the major axis of this ellipsoid. Our analysis supports the conclusion that variations in SFH are the dominant influence on present-day galaxy colours, and that the nature of this influence is strikingly simple.

scholarly journals Stochastic modelling of star-formation histories II: star-formation variability from molecular clouds and gas inflow

2020 ◽  
Vol 497 (1) ◽  
pp. 698-725 ◽  
Author(s):  
Sandro Tacchella ◽  
John C Forbes ◽  
Neven Caplar
Keyword(s):  
Life Cycle ◽  
Star Formation ◽  
Time Scales ◽  
Time Scale ◽  
Molecular Clouds ◽  
Star Formation History ◽  
Small Scale ◽  
Inflow Rate ◽  
Wide Range ◽  
The Galaxy

ABSTRACT A key uncertainty in galaxy evolution is the physics regulating star formation, ranging from small-scale processes related to the life-cycle of molecular clouds within galaxies to large-scale processes such as gas accretion on to galaxies. We study the imprint of such processes on the time-variability of star formation with an analytical approach tracking the gas mass of galaxies (‘regulator model’). Specifically, we quantify the strength of the fluctuation in the star-formation rate (SFR) on different time-scales, i.e. the power spectral density (PSD) of the star-formation history, and connect it to gas inflow and the life-cycle of molecular clouds. We show that in the general case the PSD of the SFR has three breaks, corresponding to the correlation time of the inflow rate, the equilibrium time-scale of the gas reservoir of the galaxy, and the average lifetime of individual molecular clouds. On long and intermediate time-scales (relative to the dynamical time-scale of the galaxy), the PSD is typically set by the variability of the inflow rate and the interplay between outflows and gas depletion. On short time-scales, the PSD shows an additional component related to the life-cycle of molecular clouds, which can be described by a damped random walk with a power-law slope of β ≈ 2 at high frequencies with a break near the average cloud lifetime. We discuss star-formation ‘burstiness’ in a wide range of galaxy regimes, study the evolution of galaxies about the main sequence ridgeline, and explore the applicability of our method for understanding the star-formation process on cloud-scale from galaxy-integrated measurements.

scholarly journals The star formation history of the Fornax dwarf spheroidal galaxy

2009 ◽  
Vol 5 (S262) ◽  
pp. 353-354
Author(s):  
Enrico V. Held ◽  
Eline Tolstoy ◽  
Luca Rizzi ◽  
Mary Cesetti ◽  
Andrew A. Cole ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Stellar Population ◽  
Main Sequence ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Stellar Content ◽  
Formation History ◽  
First Results ◽  
History Of

AbstractWe present the first results of a comprehensive HST study of the star-formation history of Fornax dSph, based on WFPC2 imaging of 7 Fornax fields. Our observations reach the oldest main-sequence turnoffs, allowing us to address fundamental questions of dwarf galaxy evolution, such as the spatial variations in the stellar content, and whether the old stellar population is made up of stars formed in a very early burst or the result of a more continuous star formation.

Propeties of H alpha emitters at z ∼ 2.3: Derivation of H alpha luminosity from multi-band photometry

2019 ◽  
Vol 15 (S341) ◽  
pp. 316-317
Author(s):  
Yasunori Terao ◽  
Lee Spitler ◽  
Kentaro Motohara
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Broad Band ◽  
Star Formation History ◽  
Dust Extinction ◽  
Large Numbers ◽  
Formation History ◽  
Luminous Galaxies ◽  
History Of ◽  
Individual Galaxy

AbstractThe measurement of Hα luminosity for large numbers of galaxies is important to investigate recent star formation history of galaxies. With SED fitting that includes emission line templates, we extract individual galaxy Hα luminosities from broad-band photometry. We compare Hα luminosity function with the result of a narrow-band survey, HiZELS, and find there are more luminous galaxies in Hα than previously reported. As a result, our derived star formation rate density at z ∼ 2.3 turns out to be 2.2 times higher than previous studies. Most of the offset in the results can be explained by missing Hα in the HiZELS photometric aperture and different methods for dust extinction correction.

scholarly journals The AGN contribution to the UV–FIR luminosities of interacting galaxies and its role in identifying the main sequence

2020 ◽  
Vol 499 (3) ◽  
pp. 4325-4369
Author(s):  
Andrés F Ramos Padilla ◽  
M L N Ashby ◽  
Howard A Smith ◽  
Juan R Martínez-Galarza ◽  
Aliza G Beverage ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Far Infrared ◽  
Stellar Mass ◽  
Spectral Energy ◽  
Star Forming ◽  
Nuclear Regions ◽  
The Impact

ABSTRACT Emission from active galactic nuclei (AGNs) is known to play an important role in the evolution of many galaxies including luminous and ultraluminous systems (U/LIRGs), as well as merging systems. However, the extent, duration, and exact effects of its influence are still imperfectly understood. To assess the impact of AGNs on interacting systems, we present a spectral energy distribution (SED) analysis of a sample of 189 nearby galaxies. We gather and systematically re-reduce archival broad-band imaging mosaics from the ultraviolet to the far-infrared using data from GALEX, SDSS, 2MASS, IRAS, WISE, Spitzer, and Herschel. We use spectroscopy from Spitzer/IRS to obtain fluxes from fine-structure lines that trace star formation and AGN activity. Utilizing the SED modelling and fitting tool cigale, we derive the physical conditions of the interstellar medium, both in star-forming regions and in nuclear regions dominated by the AGN in these galaxies. We investigate how the star formation rates (SFRs) and the fractional AGN contributions (fAGN) depend on stellar mass, galaxy type, and merger stage. We find that luminous galaxies more massive than about $10^{10} \,\rm {M}_{*}$ are likely to deviate significantly from the conventional galaxy main-sequence relation. Interestingly, infrared AGN luminosity and stellar mass in this set of objects are much tighter than SFR and stellar mass. We find that buried AGNs may occupy a locus between bright starbursts and pure AGNs in the fAGN–[Ne v]/[Ne ii] plane. We identify a modest correlation between fAGN and mergers in their later stages.

scholarly journals Old main-sequence turnoff photometry in the SMC: Star Formation History and Chemical Enrichment Law

2006 ◽  
Vol 2 (S241) ◽  
Author(s):  
Noelia E. D. Noël ◽  
Carme Gallart ◽  
Antonio Aparicio ◽  
Sebastián L. Hidalgo ◽  
Ricardo Carrera ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Star Formation History ◽  
Chemical Enrichment ◽  
Formation History

scholarly journals The spatially resolved star formation history of mergers

2017 ◽  
Vol 607 ◽  
pp. A70 ◽  
Author(s):  
C. Cortijo-Ferrero ◽  
R. M. González Delgado ◽  
E. Pérez ◽  
R. Cid Fernandes ◽  
R. García-Benito ◽  
...  
Keyword(s):  
Star Formation ◽  
Time Scales ◽  
Time Scale ◽  
Star Formation Rate ◽  
Early Stage ◽  
Formation Rate ◽  
Small Sample ◽  
Star Formation History ◽  
Spatially Resolved ◽  
Formation History

This paper presents the spatially resolved star formation history (2D-SFH) of a small sample of four local mergers: the early-stage mergers IC 1623, NGC 6090, and the Mice, and the more advanced merger NGC 2623, by analyzing IFS data from the CALIFA survey and PMAS in LArr mode. Full spectral fitting techniques are applied to the datacubes to obtain the spatially resolved mass growth histories, the time evolution of the star formation rate intensity (ΣSFR), and the local specific star formation rate (sSFR), over three different time scales (30 Myr, 300 Myr, and 1 Gyr). The results are compared with non-interacting Sbc–Sc galaxies, to quantify if there is an enhancement of the star formation and to trace its time scale and spatial extent. Our results for the three LIRGs (IC 1623 W, NGC 6090, and NGC 2623) show that a major phase of star formation is occurring in time scales of 107 yr to few 108 yr, with global SFR enhancements of between approximately two and six with respect to main-sequence star forming (MSSF) galaxies. In the two early-stage mergers IC 1623 W and NGC 6090, which are between first pericentre passage and coalescence, the most remarkable increase of the SFR with respect to non-interacting spirals occurred in the last 30 Myr, and it is spatially extended, with enhancements of factors between two and seven both in the centres (r < 0.5 half light radius, HLR), and in the disks (r > 1 HLR). In the more advanced merger NGC 2623 an extended phase of star formation occurred on a longer time scale of ~1 Gyr, with a SFR enhancement of a factor of approximately two-to-three larger than the one in Sbc–Sc MSSF galaxies over the same period, probably relic of the first pericentre passage epoch. A SFR enhancement in the last 30 Myr is also present, but only in NGC 2623 centre, by a factor of three. In general, the spatially resolved SFHs of the LIRG-mergers are consistent with the predictions from high spatial resolution simulations. In contrast, the star formation in the Mice, specially in Mice B, is not enhanced but inhibited with respect to Sbc–Sc MSSF galaxies. The fact that the gas fraction of Mice B is smaller than in most non-interacting spirals, and that the Mice are close to a prograde orbit, represents a new challenge for the models, which must cover a larger space of parameters in terms of the availability of gas and the orbital characteristics.

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