The search for YSOs from ISOGAL data. Application to the l = +45 field - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2000

The search for YSOs from ISOGAL data. Application to the l = +45 field

M. Felli
  • Fonction : Auteur
G. Comoretto
  • Fonction : Auteur
L. Testi
  • Fonction : Auteur

Résumé

The 7 and 15 mu m observations of the Galaxy obtained by the ISOGAL program offer an unique possibility to investigate and separate the different populations of stars in the Galactic Plane, in particular to study the population of low flux density YSOs which could not be detected with IRAS. Considering the results obtained by ISOCAM in nearby star forming regions and in other test fields in the Galactic Plane, as well as theoretical indications, we establish criteria of general validity that can be used to select YSOs from the much larger population of Post Main Sequence (Post-MS) stars present in the ISOGAL fields. The selection is based primarily on the position of the sources in the [15] - [7]-[15] diagram, which involves only ISOGAL data and allows to select objects with IR excess as possible YSOs using the survey data alone. The criteria are applied to five ISOGAL fields centered at l ~ +45deg and b ~ 0deg, covering a total area of 0.504 deg2. The total number of point sources detected in both filters above the confidence limits of [7] < 9.5 and [15] < 8 are 386. The ISOGAL results are compared with radio observations in order to identify high luminosity YSOs out of the larger population of lower luminosity ones. We find 3 high luminosity YSOs plus 3 diffuse sources which are associated with HII regions and 35 lower luminosity YSOs. For low flux densities we find a consistent number of sources (73) detected only at 15 mu m which, according to the colour upper limit, are classified as candidate YSOs. The validity of the adopted criteria for selecting possible YSOs in the ISOGAL fields are also supported by two independent results: 1) the sources classified as YSOs and the candidate YSOs are often associated with diffuse nebulosities visible at 15 mu m, landmarks of recent star forming activity, and 2) the numbers of high luminosity and low luminosity YSOs that we have found compare well with the expectations. This is paper no. 8 in a refereed journal based on data from the ISOGAL project. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA. Table 4 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
Fichier principal
Vignette du fichier
document7.pdf (592 Ko) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

hal-04110315 , version 1 (06-06-2023)

Identifiants

Citer

M. Felli, G. Comoretto, L. Testi, A. Omont, F. Schuller. The search for YSOs from ISOGAL data. Application to the l = +45 field. Astronomy and Astrophysics - A&A, 2000, 362, pp.199-214. ⟨hal-04110315⟩
10 Consultations
2 Téléchargements

Partager

Gmail Facebook X LinkedIn More