Interactions of the Infrared bubble N4 with ITS surroundings

The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with H ii regions have been considered to be good samples for investigating triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the H ii region G11.898+0.747, analyzing its interaction with its surroundings and star formation histories therein, with the aim of determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K, mean column density of 1.7 × 1022 cm-2, mean volume density of about 4.4 × 104 cm-3, and a mean mass of 320 M⊙. In addition, from PAH emission seen at 8 μm, free-free emission detected at 20 cm, and a probability density function in special regions, we could identify clear signatures of the influence of the H ii region on the surroundings. There are hints of star formation, though further investigation is required to demonstrate that N4 is the triggering source.Fil: Liu, Hong Li. National Astronomical Observatories; ChinaFil: Li, Jin Zeng. National Astronomical Observatories; ChinaFil: Wu, Yuefang. Aix Marseille Universit; FranciaFil: Yuan, Jing Hua. National Astronomical Observatories; ChinaFil: Liu, Tie. Korea Astronomy and Space Science Institute; Corea del SurFil: Dubner, Gloria Mabel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Paron, Sergio Ariel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Ortega, Martin Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: molinari, Sergio. Istituto di Astrofisica e Planetologia Spaziali; ItaliaFil: Huang, Maohai. National Astronomical Observatories; ChinaFil: Zavagno, Annie. Aix Marseille Universit; FranciaFil: Samal, Manash R.. Aix Marseille Universit; FranciaFil: Huang, Ya Fang. National Astronomical Observatories; ChinaFil: Zhang, Si Ju. National Astronomical Observatories; Chin