## Detalles de publicación

PP 016013

## On recent SFR calibrations and the constant SFR approximation

IAC, ULL, IAA, ASPID

Star Formation Rate (SFR) inferences are based in the so-called constant SFR

approximation, where synthesis models are require to provide a calibration; we

aims to study the key points of such approximation to produce accurate SFR

inferences. We use the intrinsic algebra used in synthesis models, and we

explore how SFR can be inferred from the integrated light without any

assumption about the underling Star Formation history (SFH). We show that the

constant SFR approximation is actually a simplified expression of more deeper

characteristics of synthesis models: It is a characterization of the evolution

of single stellar populations (SSPs), acting the SSPs as sensitivity curve over

different measures of the SFH can be obtained. As results, we find that (1) the

best age to calibrate SFR indices is the age of the observed system (i.e. about

13Gyr for z=0 systems); (2) constant SFR and steady-state luminosities are not

requirements to calibrate the SFR; (3) it is not possible to define a SFR

single time scale over which the recent SFH is averaged, and we suggest to use

typical SFR indices (ionizing flux, UV fluxes) together with no typical ones

(optical/IR fluxes) to correct the SFR from the contribution of the old

component of the SFH, we show how to use galaxy colors to quote age ranges

where the recent component of the SFH is stronger/softer than the older

component.

Particular values of SFR calibrations are (almost) not affect by this work,

but the meaning of what is obtained by SFR inferences does. In our framework,

results as the correlation of SFR time scales with galaxy colors, or the

sensitivity of different SFR indices to sort and long scale variations in the

SFH, fit naturally. In addition, the present framework provides a theoretical

guide-line to optimize the available information from data/numerical

experiments to improve the accuracy of SFR inferences.

approximation, where synthesis models are require to provide a calibration; we

aims to study the key points of such approximation to produce accurate SFR

inferences. We use the intrinsic algebra used in synthesis models, and we

explore how SFR can be inferred from the integrated light without any

assumption about the underling Star Formation history (SFH). We show that the

constant SFR approximation is actually a simplified expression of more deeper

characteristics of synthesis models: It is a characterization of the evolution

of single stellar populations (SSPs), acting the SSPs as sensitivity curve over

different measures of the SFH can be obtained. As results, we find that (1) the

best age to calibrate SFR indices is the age of the observed system (i.e. about

13Gyr for z=0 systems); (2) constant SFR and steady-state luminosities are not

requirements to calibrate the SFR; (3) it is not possible to define a SFR

single time scale over which the recent SFH is averaged, and we suggest to use

typical SFR indices (ionizing flux, UV fluxes) together with no typical ones

(optical/IR fluxes) to correct the SFR from the contribution of the old

component of the SFH, we show how to use galaxy colors to quote age ranges

where the recent component of the SFH is stronger/softer than the older

component.

Particular values of SFR calibrations are (almost) not affect by this work,

but the meaning of what is obtained by SFR inferences does. In our framework,

results as the correlation of SFR time scales with galaxy colors, or the

sensitivity of different SFR indices to sort and long scale variations in the

SFH, fit naturally. In addition, the present framework provides a theoretical

guide-line to optimize the available information from data/numerical

experiments to improve the accuracy of SFR inferences.