POISSON project

Abstract

Context. As part of the Protostellar Optical-Infrared Spectral Survey On NTT (POISSON) project, we present the results of the analysis of low-resolution near-IR spectroscopic data (0.9-2.4 μm) of two samples of young stellar objects in the Lupus (52 objects) and Serpens (17 objects) star-forming clouds, with masses in the range of 0.1 to 2.0 M and ages spanning from 10 5 to a few 10 7 yr.Aims. After determining the accretion parameters of the targets by analysing their H i near-IR emission features, we added the results from the Lupus and Serpens clouds to those from previous regions (investigated in POISSON with the same methodology) to obtain a final catalogue (143 objects) of mass accretion rate values (Ṁ acc ) derived in a homogeneous and consistent fashion. Our final goal is to analyse howṀ acc correlates with the stellar mass (M * ) and how it evolves in time in the whole POISSON sample. Methods. We derived the accretion luminosity (L acc ) andṀ acc for Lupus and Serpens objects from the Brγ (Paβ in a few cases) line by using relevant empirical relationships available in the literature that connect the H i line luminosity and L acc . To minimise the biases that arise from adopting literature data that are based on different evolutionary models and also for self-consistency, we re-derived mass and age for each source of the POISSON samples using the same set of evolutionary tracks.Results. We observe a correlationṀ acc ∼ M 2.2 * between mass accretion rate and stellar mass, similarly to what has previously been observed in several star-forming regions. We find that the time variation ofṀ acc is roughly consistent with the expected evolution of the accretion rate in viscous disks, with an asymptotic decay that behaves as t −1.6 . However,Ṁ acc values are characterised by a large scatter at similar ages and are on average higher than the predictions of viscous models. Conclusions. Although part of the scattering may be related to systematics due to the employed empirical relationship and to uncertainties on the single measurements, the general distribution and decay trend of theṀ acc points are real. These findings might be indicative of a large variation in the initial mass of the disks, of fairly different viscous laws among disks, of varying accretion regimes, and of other mechanisms that add to the dissipation of the disks, such as photo-evaporation.

X-Shooter study of accretion in Chamaeleon I

“…Tables A.1-A.2). Accretion rate estimates are only available for some targets (e.g., Antoniucci et al 2011Antoniucci et al , 2014Frasca et al 2015). Here we compare these results with our estimates.…”

“…3 shows the comparison between the values oḟ M acc for Chamaeleon I targets derived here and those from the POISSON survey (Antoniucci et al 2011(Antoniucci et al , 2014 and the Gaia-ESO survey (GES, Frasca et al 2015). The POISSON survey used infrared spectra and the luminosity of the Brγ and Paβ emission lines to derive L acc , and obtainedṀ acc assuming the stellar parameters for the targets from Luhman (2007).…”

“…This mass accretion rate (Ṁ acc , e.g., Hartmann et al 1998) may be compared to the stellar and disk properties to test the predictions of models of disk evolution. Relations between the accretion luminosity (L acc ) and stellar luminosity (L , e.g., Natta et al 2006;Clarke & Pringle 2006;Rigliaco et al 2011a;Manara et al 2012) and betweenṀ acc and stellar mass (M , e.g., Muzerolle et al 2003;Mohanty et al 2005;Natta et al 2006;Herczeg & Hillenbrand 2008;Antoniucci et al 2011Antoniucci et al , 2014Manara et al 2012;Alcalá et al 2014;Ercolano et al 2014;Frasca et al 2015) are frequently derived to examine the dependence of accretion on the properties of the central star. Accretion has sometimes been found to correlate with age (e.g., Hartmann et al 1998;Sicilia-Aguilar et al 2010;Antoniucci et al 2014), although ages of individual young stars in a given This work is based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 084.C-1095 and 094.C-0913.…”

“…Recent studies have also demonstrated that L acc derived from several emission lines measured simultaneously lead to results compatible, although with a larger scatter, with more direct methods (Rigliaco et al 2012;Alcalá et al 2014). Therefore, measuringṀ acc from the luminosity of emission lines is a method that is being extensively used in the literature (e.g., Mohanty et al 2005;Natta et al 2006;Fang et al 2009;Costigan et al 2012;Antoniucci et al 2011Antoniucci et al , 2014Biazzo et al 2014).…”

The small-scale HH34 IRS jet as seen by X-shooter

“…Although the real origin of these lineswhether in accretion columns and spots, or in ionized winds -is still uncertain, it has been shown that their intrinsic luminosity scales with L acc in T Tauri stars (Herczeg & Hillenbrand 2008;Alcalá et al 2014). As such they have been widely used to indirectly derive L acc and consequently the mass accretion rate (Ṁ acc ) in sources with known stellar parameters (e.g., Antoniucci et al 2014b). Using the assumption that the same relationships between L line vs. L acc also hold in the more embedded class I sources, we can estimateṀ acc in HH34 IRS from the dereddened line luminosities.…”