Esraa Khafagy
Career Stage
Early Career Professional (includes early career lecturers, science communicators, industry professionals and other early career Geophysics/Astronomy professionals outside of Academia)
Poster Abstract
The evolution of high mass stars has an extreme importance in Astrophysics, due to its influence in galaxy formation and the interstellar medium. Throughout their lifetime massive stars eject material into the surrounding environment through stellar winds, outflows, ultraviolet (UV) and supernovae. A star can be considered a massive one starting from 8 times the sun's mass. There are some difficulties faced during studying high mass formation 1) It takes place at large distance in the galactic plane (larger than 1Kpc) 2) Formed inside high density clouds 3) Radiation pressure from massive proto-stellar objects is expected to stop the accretion process when the star reaches the limit of 10 times the sun’s mass. In this studies we trace an area through radio emission lines where a massive star is being born to a better understanding of massive stars’ evolution
Plain text summary
Motivation
Studying high mass stars has great importance in the field of Astronomy and Astrophysics. They influence galaxies' formation and supply the universe with heavy elements. They are found at great distances inside dusty dense clouds, making it difficult to study their formation in optical bands (Fig. 1). So, in this study we trace high mass star formation by observing one of the indicators of their presence, the Laser brother in the radio band, Microwaves Amplification by Stimulated Emission of Radiation (MASER). The strong and compact nature of MASER sources makes them good tracers of material surrounding pre-stellar cores and their physical properties and morphology
Aim of Study
Our main aim is to use maser emission to trace the early evolutionary stages of high mass stars in order to build understated how they form and build a classification for high mass star forming objects to figure out their stages of revolutionary process.
Target object
We used Infrared (IR) radiation intensity to choose an object that is expected to be a forming massive star in its early evolution. Our target object (IRAS 18144-1723) is taken from the Infrared Astronomical Satellite catalogue. It has an IR intensity similar to those with ionized Hydrogen HII, a sign of the presence of a Proto-star with radiation ionizing its surrounding. However, we have not yet detected an HII region toward this object, so we suppose that it is in earlier stage than other sources with HII regions.
Observation
The maser used in this study is methanol (CH3OH) maser and the observation was done by the Multi-Element Radio Linked Interferometer Network (MERLIN) which is an interferometer array of radio telescopes spread across England. This allows the study of sources which need a higher angular resolution than that achieved by using a single dish telescope.
The 6.7 GHz methanol line was observed in a spectral bandwidth of 0.25 MHz centred at a gas velocity of 56 km/s with respect to the Local Standard of Rest.
What did we get?
We detected a total of 52 maser components of the 6.7 GHz methanol maser towards IRAS 18144-1723 which were grouped according to spatial and spectral distribution and averaged into 9 features.
The strongest maser feature has velocity of 51 km/s. Varricatt et al. (2010) present a H2 image showing a bowshock-like feature about 18″ to the west of the IRAS position. Gomez-Ruiz et al. (2016) observed methanol masers at 44 GHz and detected 11 maser spots. Nine of their detected maser spots fall in a bunch within ~5 arc-sec of the bow shock, seeming to trace a shock from a deeply embedded object. Our observations at 6.7 GHz detected 9 methanol maser features located more than 1 arcsecond north of the 44 GHz maser. In a more recent study, Varricatt et al (2018) used near infra-red imaging to find two embedded sources defined as A & B . A is well detected in K-band (2.2 micron) with source B is weak. The 6.7 GHz Methanol maser is associated with the weak K-band source B
Conclusion
We detected 9 maser features of 6.7 GHz methanol towards the region of IRAS18144-1723. The strongest maser feature of 20 Jy is at velocity 51 km/s. The detected maser features are close to the weaker IR K-band source which indicates that they are associated with a proto-star in an earlier stage of its evolution that strong IR source to the east.
Studying high mass stars has great importance in the field of Astronomy and Astrophysics. They influence galaxies' formation and supply the universe with heavy elements. They are found at great distances inside dusty dense clouds, making it difficult to study their formation in optical bands (Fig. 1). So, in this study we trace high mass star formation by observing one of the indicators of their presence, the Laser brother in the radio band, Microwaves Amplification by Stimulated Emission of Radiation (MASER). The strong and compact nature of MASER sources makes them good tracers of material surrounding pre-stellar cores and their physical properties and morphology
Aim of Study
Our main aim is to use maser emission to trace the early evolutionary stages of high mass stars in order to build understated how they form and build a classification for high mass star forming objects to figure out their stages of revolutionary process.
Target object
We used Infrared (IR) radiation intensity to choose an object that is expected to be a forming massive star in its early evolution. Our target object (IRAS 18144-1723) is taken from the Infrared Astronomical Satellite catalogue. It has an IR intensity similar to those with ionized Hydrogen HII, a sign of the presence of a Proto-star with radiation ionizing its surrounding. However, we have not yet detected an HII region toward this object, so we suppose that it is in earlier stage than other sources with HII regions.
Observation
The maser used in this study is methanol (CH3OH) maser and the observation was done by the Multi-Element Radio Linked Interferometer Network (MERLIN) which is an interferometer array of radio telescopes spread across England. This allows the study of sources which need a higher angular resolution than that achieved by using a single dish telescope.
The 6.7 GHz methanol line was observed in a spectral bandwidth of 0.25 MHz centred at a gas velocity of 56 km/s with respect to the Local Standard of Rest.
What did we get?
We detected a total of 52 maser components of the 6.7 GHz methanol maser towards IRAS 18144-1723 which were grouped according to spatial and spectral distribution and averaged into 9 features.
The strongest maser feature has velocity of 51 km/s. Varricatt et al. (2010) present a H2 image showing a bowshock-like feature about 18″ to the west of the IRAS position. Gomez-Ruiz et al. (2016) observed methanol masers at 44 GHz and detected 11 maser spots. Nine of their detected maser spots fall in a bunch within ~5 arc-sec of the bow shock, seeming to trace a shock from a deeply embedded object. Our observations at 6.7 GHz detected 9 methanol maser features located more than 1 arcsecond north of the 44 GHz maser. In a more recent study, Varricatt et al (2018) used near infra-red imaging to find two embedded sources defined as A & B . A is well detected in K-band (2.2 micron) with source B is weak. The 6.7 GHz Methanol maser is associated with the weak K-band source B
Conclusion
We detected 9 maser features of 6.7 GHz methanol towards the region of IRAS18144-1723. The strongest maser feature of 20 Jy is at velocity 51 km/s. The detected maser features are close to the weaker IR K-band source which indicates that they are associated with a proto-star in an earlier stage of its evolution that strong IR source to the east.
Poster file
Poster Title
Studying High Mass Star Forming Regions Through Radio Emission Lines
Url
esraakhafagy@gstd.sci.cu.edu.eg / https://www.linkedin.com/in/israa-khafagy-b53270106/