5.B Additional literature data
6.4 New data in the ρ -Ophiucus embedded complex
6.4.3 Accretion properties of ρ -Ophiucus young stellar objects
6. Accretion as a function of stellar properties in nearby star forming regions
Table 6.8: Accretion luminosity and mass accretion rates of theρ-Oph Class II YSOs Object logLacc logM˙acc Detected lines
[L⊙] [M⊙/yr] [#]
ISO−Oph023 -3.76 -10.22 4
ISO−Oph030 -2.85 -9.34 6
ISO−Oph032 -3.82 -10.21 9
ISO−Oph033 -5.10 -11.38 1
ISO−Oph037 -1.78 -9.12 4
ISO−Oph072 -0.97 -8.33 8
ISO−Oph087 <-3.10 <-9.99 0
ISO−Oph094 -3.70 -11.33 1
ISO−Oph102 -2.71 -9.28 7
ISO−Oph115 -2.13 -9.50 2
ISO−Oph117 -2.56 -9.43 3
ISO−Oph123 -1.93 -8.97 11
ISO−Oph160 -3.24 -9.88 4
ISO−Oph164 -3.75 -10.30 8
ISO−Oph165 -3.00 -10.38 2
ISO−Oph176 -4.45 -11.04 1
ISO−Oph193 -2.75 -9.54 3
Notes.M∗and age are derived using the evolutionary tracks of Baraffe et al. (1998). The last column reports the number of detected emission lines in the spectra used to deriveLacc.
6.4 New data in the ρ-Ophiucus embedded complex
5 4321
ISO-Oph023 ISO-Oph030 ISO-Oph032
5 4 3 2 1
log (L
acc/L
¯)
ISO-Oph033ISO-Oph037 ISO-Oph072
CaK Hδ Hγ Hβ 587HeI Hα 667HeI Paδ Paγ Paβ Brγ 5
4321
ISO-Oph087 CaK Hδ Hγ Hβ 587HeI Hα 667HeI Paδ Paγ Paβ Brγ
ISO-Oph094 CaK Hδ Hγ Hβ 587HeI Hα 667HeI Paδ Paγ Paβ Brγ ISO-Oph102
Figure 6.13: Accretion luminosity derived from various emission lines luminosity for theρ-Oph targets. Each subplot shows the value of log(Lacc/L⊙) derived using the various indicators reported on the x-axis (CaK, Hδ, Hγ, Hβ, Heλ587nm, Hα, Heλ667nm, Paδ, Paγ, Paβ, Brγ). The red solid line is the average values obtained from the detected lines, while the dashed lines are the 1σstandard deviation of this value.
deviation of these values. Figures 6.13-6.14 show the value ofLacc determined with each line for all the targets. The accretion luminosity for the targets are reported in the second column of Table 6.8, while the number of detected emission lines used to calculateLacc is available in the last column.
I use the value of Lacc determined using the emission lines as the final value also for ISO-Oph032 and ISO-Oph123, for which my fitting procedure could determine directly Lacc from the fit of the UVB spectrum. This choice is done to keep the results for the targets consistent. Moreover, the value of Lacc determined for ISO-Oph032 from the fit-ting procedure (log(Lacc/L⊙)=-3.87) is compatible with that determined with the emission lines (log(Lacc/L⊙)=-3.82). For ISO-Oph123, the value determined from the fit of the UV-excess (log(Lacc/L⊙)=-1.22) is much higher than the one obtained from the luminosity of the emission lines (log(Lacc/L⊙)=-1.93). However, as I discussed in the previous section, this difference could be due to the bad fit of the Balmer continuum and to an underestimation of the stellar luminosity with the fitting procedure.
In the spectrum of ISO-Oph087 there are no emission lines. Therefore it is not possible
6. Accretion as a function of stellar properties in nearby star forming regions
5 4321
ISO-Oph115 ISO-Oph117 ISO-Oph123
5 4 3 2 1
log (L
acc/L
¯)
ISO-Oph160 ISO-Oph164 CaK Hδ Hγ Hβ 587HeI Hα 667HeI Paδ Paγ Paβ Brγ ISO-Oph165
CaK Hδ Hγ Hβ 587HeI Hα 667HeI Paδ Paγ Paβ Brγ 5
4321
ISO-Oph176 CaK Hδ Hγ Hβ 587HeI Hα 667HeI Paδ Paγ Paβ Brγ ISO-Oph193
Figure 6.14: Accretion luminosity derived from various emission lines luminosity for theρ-Oph targets. Same as Fig. 6.13.
to determine the accretion rate of this object. I estimate an upper limit on the accretion rate from the upper limit on the Hαline and use this value in the analysis.
From the values ofLacc and the stellar parametersM⋆ andR⋆ derived as in the previous section and reported in Table 6.7, I derive M˙acc using Eq. (1.2). This is reported for every object in the third column of Table 6.8. In Fig. 6.15 I show the values ofM˙accvsM⋆derived here (black points) and those from Natta et al. (2004, 2006) and corrected for distance by Rigliaco et al. (2011a) (gray points). I also report the best fit of the M˙acc-M⋆ relation for the Lupus targets derived by Alcalá et al. (2014) as a reference. The values derived here for theρ-Oph sample are reported withsmall filled circlesfor targets with uncertain stellar parameters and with open circles for objects with strong veiling. In Fig. 6.16, instead, I show only the data for the targets in common, withred crosses reporting the values from the literature. With respect to the results of Natta et al. (2004, 2006), the values ofM⋆ are different in many cases, and this is due to the more precise derivation of stellar parameters done here. In general, the values ofM˙acc derived here are lower, and this could be due in part to the differentLacc-Lline relations adopted here, and in part to the better derivation of the extinction. The values ofM⋆derived here are, instead, larger than those in the literature for many targets. However, the newly estimated values of M⋆ are compatible with those
6.4 New data in the ρ-Ophiucus embedded complex
2.0 1.5 1.0 0.5 0.0 0.5
log(M /M
¯)
12 11 10 9 8 7
log (
˙ Mac
c
/[M
¯/yr ])
Natta+06 this work
Figure 6.15: Mass accretion rate as a function of mass for theρ-Oph sample. Values derived for the objects analyzed here are reported with black markers, where big filled circles are used for objects with reliable stellar properties estimates,small filled circlesfor those with uncertain stellar parameters, andopen circles for targets with strong veiling. Values from the literature forρ-Oph (Natta et al., 2004, 2006, corrected for distance as in Rigliaco et al. 2011a) are shown with gray symbols. Downward arrows are used for upper limits. The continuous line represents the linear fit of this relation for the Lupus sample (see Equation 6.3).
The dashed lines represent the 1σ deviation from the fit. Average error bars are shown in the upper left corner.
of Natta et al. (2004, 2006) for the vast majority of objects with reliable stellar parameters estimate derived in my analysis. The largest differences are found for objects with highly uncertain SpT, as expected. In one case, ISO-Oph176, the spectrum analyzed here present a detected emission line (Hα) and I am able to measure a value of M˙acc lower than the upper limit reported by Natta et al. (2004, 2006). This object, however, has a value ofM˙acc significantly lower than the one expected by theM˙acc-M⋆relation of Lupus for objects with the same mass. This measurement is probably strongly affected by chromospheric emission contribution in the line luminosity and thus uncertain, as the value of Lacc is compatible to the value ofLacc,noise determined in Chapter 3 from the luminosity of the emission lines of Class III YSOs. However, this object could also possibly be a low-accreting object with a significantly gas-depleted disk. On the other hand, I do not detect any line in the spectrum of ISO-Oph087, for which Natta et al. (2004, 2006) report a value ofLacc from the measurement of the Paβline. One possibility is that this object is variable, and the large difference in the value could be in part due to variability and in part to the low luminosity derived here for this target.
Interestingly, the newly derived values of M˙acc are compatible on the M˙acc-M⋆ plane with the best fit relation of the Lupus sample at least for nine of the ten spectra with good
6. Accretion as a function of stellar properties in nearby star forming regions
2.0 1.5 1.0 0.5 0.0 0.5
log(M /M¯)
12 11 10 9 8 7
log(
˙ Mac
c/[M¯/yr])
Natta+06 this work
Figure 6.16: Comparison of mass accretion rate as a function of mass for theρ-Oph sample with the literature data. Values from the literature forρ-Oph (Natta et al., 2004, 2006, corrected for distance as in Rigliaco et al. 2011a) for the targets analyzed here are shown withred crosses. The red lines connect these values with those derived here for the same targets. The other symbols are as in Fig. 6.15.
SNR and not strong veiling and for the two strongly veiled ones. In particular, the spread of values on this plot at any mass decreases with respect to the one of the same objects with the values derived by Natta et al. (2004, 2006). The five objects with uncertain stellar parameters (four small black circles and one black upper limit) are all located below the 1σdeviation from the best-fit line. However, given the uncertainties on their stellar param-eters, the values ofM˙acc derived for these targets are probably not accurate, and possibly underestimated, given that theirL⋆ are probably underestimated, as well.
The smaller spread of M˙acc at anyM⋆ found with the new X-Shooter spectra and the analysis described in this section suggest that most of the spread observed in the past was due to the methodology used. In particular, in the case of ρ-Oph the uncertain stellar parameter and the possibility to use only one or two emission lines to derive Lacc was a severe limitation of previous investigations. However, the small sample analyzed in this section does not allow to make final statements on this. I refer to Sect. 6.6 for a more detailed discussion including all the samples analyzed in this Chapter and in this Thesis.