What procedure should be used to classify the line profiles? Reipurth, Pedrosa & Lago (1996) review, briefly, existing classification schemes for the H Alpha line and propose a new one, which tries to reflect an underlying physical process as well as being able to deal with a greater variety of line profiles. Given that all Pa Beta and Br Gamma line profiles displayed in Figures 5.1 and 5.2 fit in one of the classes of that classification scheme there is no need to introduce yet another one. Furthermore, this will allow a straightforward comparison between what is found for H Alpha and what is found for these near infrared lines.
The Reipurth, Pedrosa & Lago (1996) classification scheme divides the line profiles into four main types: Type I profiles are generally symmetric showing no evidence for absorption features or only very slight influence from those; Type II profiles show two peaks with the intensity of the second peak exceeding half the strength of the main peak; Type III profiles show two peaks with the intensity of the second peak being less than half the strength of the main peak and finally Type IV profiles, which show an absorption feature beyond which no emission is seen. To Types II, III and IV the letters B or R are appended, depending on the location of the secondary peak/absorption feature relative to the main peak: if blueshifted a B is appended, if redshifted an R is added. Note that Type IV B correspond to normal P Cygni profiles and Type IV R correspond to inverse P Cygni profiles (henceforth IPC).
The classification of the Pa Beta and Br Gamma (hereafter referred to as NIR lines) line profiles displayed in Figures 5.1 and 5.2 is presented in Tables 5.1 and 5.2 respectively.
Table 5.2: Classification of the Br Gamma emission line
profiles according to the classification scheme developed by Reipurth,
Pedrosa & Lago (1996) for the T Tauri stars. The total number of
stars with Br Gamma in emission is 30.
For a few stars the Pa Beta and/or Br Gamma lines were observed more than once (refer to Section 5.4.7). The classification presented in Table 5.1 (Pa Beta ) refers to data obtained during the second observing run, ie. December 1995. The reason for this is that during the October 1994 campaign, only five T Tauri stars were observed at Pa Beta , all of which were also observed during the second campaign and with a much higher signal-to-noise ratio. The classification presented in Table 5.2 (Br Gamma ) refers mostly to data obtained during the December 1995 observing run. For stars observed in both October 1994 and December 1995 (DF Tau, DK Tau, DR Tau, GG Tau, GI Tau, RW Aur and UY Aur), only the line profiles with higher signal-to-noise ratio (from Dec. 95) are classified.
The subject of variability in the line profiles will be left for Section 5.4.7, however a few remarks are relevant to the present discussion. The amount of variation present in the Pa Beta line profile of the stars observed twice during the 1995 campaign is such that the type of line profile does not change. However, for some stars, significant changes are seen in spectra taken 14 months apart, ie. in October 1994 and in December 1995. The Pa Beta line profile of GK Tau changes from Type I to a Type IV R and DR Tau's Pa Beta profile changes from Type I to Type II R. The Pa Beta profiles of DL Tau, DG Tau and GI Tau remain very similar. The Br Gamma profile of RW Aur changes from Type I to Type IV R while DR Tau and GG Tau Br Gamma line profiles do not change their classification. These changes do not alter the statistics presented above significantly, however they should be borne in mind. The observed line variability, or lack of it, will be discussed further in Section 5.4.7.
The main conclusions that can be taken from Tables 5.1 and 5.2 are the following: most line profiles are generally symmetric, especially the Br Gamma line profiles, where 73% of the profiles are classified as Type I; both Pa Beta and Br Gamma line profiles lack blueshifted absorptions (only one star - CW Tau - displays any sort of absorption in the blue wing and only in Pa Beta); nearly one third of the Br Gamma profiles have redshifted absorptions, with this number being even higher for the Pa Beta profiles, of which 44% display redshifted absorptions.
These results are in complete contrast to what is found at H Alpha by Reipurth, Pedrosa & Lago (1996). These authors find that 54% of the H Alpha line profiles in their sample have blueshifted absorptions whereas redshifted absorption features are found in 21% of those profiles. The remaining 25% of the profiles are classified as Type I. The H Alpha lines are indicators for the presence of a wind, as the high frequency of absorptions in the blue testify. At H Alpha, not only the blueshifted absorption features are interpreted to form in a wind, but also emission is commonly attributed to outflowing material. The almost complete lack of 'B' type profiles in the NIR lines raises doubts about the emission in these lines rising in a wind scenario. NIR lines with IPC profiles indicate that infall is occurring in that star and indicate that even the emission component in the NIR lines might arise in an accretion flow.
In order to try to establish where Pa Beta and Br Gamma are formed, using the data set presented in this work, one needs more quantitative information about the line profiles.
