Correlation between the spatial distribution of circumstellar disks and massive stars in the young open cluster NGC 6611. II: Cluster members selected with Spitzer/IRAC

TL;DR

This study investigates how UV radiation from massive stars influences the evolution of circumstellar disks in the young open cluster NGC 6611, using Spitzer/IRAC data to identify cluster members with disks and analyze their spatial distribution.

Contribution

The paper extends previous work by identifying additional cluster members with disks using Spitzer/IRAC data and confirms the impact of UV radiation on disk evolution in NGC 6611.

Findings

Identified 458 candidate disk-bearing members, including 146 new detections.

Confirmed UV radiation from massive stars affects circumstellar disk evolution.

Detected consistent infrared excesses indicating emission from the inner disk regions.

Abstract

Context: the observations of the proplyds in the Orion Nebula Cluster, showing clear evidence of ongoing photoevaporation, have provided a clear proof about the role of the externally induced photoevaporation in the evolution of circumstellar disks. NGC 6611 is an open cluster suitable to study disk photoevaporation, thanks to its large population of massive members and of stars with disk. In a previous work, we obtained evidence of the influence of the strong UV field generated by the massive cluster members on the evolution of disks around low-mass Pre-Main Sequence members. That work was based on a multi-band BVIJHK and X-ray catalog purposely compiled to select the cluster members with and without disk. Aims: in this paper we complete the list of candidate cluster members, using data at longer wavelengths obtained with Spitzer/IRAC, and we revisit the issue of the effects of UV radiation on the evolution of disks in NGC 6611. Methods: we select the candidate members with disks of NGC 6611, in a field of view of 33'x34' centered on the cluster, using IRAC color-color diagrams and suitable reddening-free color indices. Besides, using the X-ray data to select Class III cluster members, we estimate the disks frequency vs. the intensity of the incident radiation emitted by massive members. Results: we identify 458 candidate members with circumstellar disks, among which 146 had not been revealed in our previous work. Comparing of the various color indices we used to select the cluster members with disk, we claim that they detect the excesses due to the emission of the same physical region of the disk: the inner rim at the dust sublimation radius. Our new results confirm that UV radiation from massive stars affects the evolution of nearby circumstellar disks.