Anatomy of the impact of a protostellar jet in the Orion Nebula

Date:
September 2, 2021
Source:
Instituto de Astrofi'sica de Canarias (IAC)
Summary:
Researchers have uncovered the physical and chemical effects of
the impact of a protostellar jet in the interior of the Orion
Nebula. The observations show evidence of compression and heating
produced by the shock front, and the destruction of dust grains,
which cause a dramatic increase in the gas phase abundance of the
atoms of iron, nickel, and other heavy elements in the Orion Nebula.



FULL STORY ==========================================================================
An international team led by researchers from the Instituto
de Astrofi'sica de Canarias (IAC) has uncovered, with an new high
degree of detail, the physical and chemical effects of the impact of a protostellar jet in the interior of the Orion Nebula. The study was made
using observations with the Very Large Telescope (VLT) and 20 years of
images with the Hubble Space Telescope (HST).

The observations show evidence of compression and heating produced
by the shock front, and the destruction of dust grains, which cause
a dramatic increase in the gas phase abundance of the atoms of iron,
nickel, and other heavy elements in the Orion Nebula. The results were
recently published in The Astrophysical Journal.


==========================================================================
The Orion Nebula, one of the known and brightest objects in the night
sky, is the nearest region of massive star formation to Earth, and it
has a complex and extensive gas structure. Some of the newborn stars
within it emit jets of gas at high speed which, when they impact their surroudings, produce shock fronts which compress and heat the nebular
gas. These impact zones are bow-shaped, and are called Herbig-Haro
objects, after their discoverers, the US astonomer George Herbig, and
the Mexican astronomer Guillermo Haro.

These objects have been observed previously in many dark nebulae,
where the cold gas is neutral, and its main source of energy is the heat generated by the shock. However, the jets of gas in the Orion Nebula are immersed in a large radiation field produced by the most massive stars in
the Trapezium of Orion, situated at the centre of the nebula. Due to this radiation the gas within the shock front and also the gas compressed after
it has passed through, is warm and ionized, and this allows us to measure precisely the physical conditions and the chemical composition of the jet.

The research carried out by a team of astronomers in Spain, Mexico and
the United States, led by Jose' Eduardo Me'ndez Delgado, a doctoral
student at the IAC and the University of La Laguna (ULL), has uncovered
the complex relations between the ionic abundances of the gas and its
physical conditions in HH204, one of the most prominent Herbig-Haro
objects in the Orion Nebula.

"Our work shows that the in the shock front of HH204 the gas abundances
of heavy elements such as iron and nickel are increased by up to 350%
compared to the values usually found in the Orion Nebula, and this allows
us to determine the proportion of other chemical elements more accurately, which contributes to an improved knowledge of the chemical evolution
in the solar neighbourhood," explains Jose' Eduardo Me'ndez Delgado,
the first author of the article.

"As well as the heavy element enrichment in the gas phase, we have
observed a heated post-shock zone which comprises a very small fraction
of the gas, and which lets us understand the different layers of the
structure of the Herbig- Haro object generated by the impact of the
shock front," says Ce'sar Esteban, and IAC researcher and a co-author
of the article.

"The origin of HH204 appears to be associated with one of the most
brilliant and star formation rich zones of the Orion Nebula, the regions
called Orion South, although there are many interactions of gas which
appear to feed it from several directions," adds William Henney, a
researcher at the Institute of Radioastronomy and Astrophysics at the
National Autonomous University of Mexico, and a co-author of the article.

"Thanks to the images of the Hubble Space Telescope we have shown that
HH204 is propagating at an angle of 32-o with the plane of the sky, which
lets us observe the compression of the gas transversely as we approach
the shock front," points out Karla Arellano Co'rdova, a researcher at
the University of Texas at Austin, and a co-author of the article.

"We have seen that the impact of these objects can be important when determining the local physical conditions in ionized nebulae. In fact,
if we don't take these effects into account we can make incorrect determinations of the chemical composition of the ionized nebulae, which
are fundamental techniques for understanding the chemical evolution
of the Universe," sums up Jorge Garci'a Rojas, an IAC researcher and a co-author of the article.

========================================================================== Story Source: Materials provided by Instituto_de_Astrofi'sica_de_Canarias_(IAC). Note: Content may be edited
for style and length.


========================================================================== Related Multimedia:
* View_of_HH204,_a_Herbig-Haro_object_in_the_Orion_Nebula,_and_of_its
apparent_companion,_HH203 ========================================================================== Journal Reference:
1. J. E. Me'ndez-Delgado, W. J. Henney, C. Esteban, J. Garci'a-Rojas,
A.

Mesa-Delgado, K. Z. Arellano-Co'rdova. Photoionized Herbig-Haro
Objects in the Orion Nebula through Deep High Spectral Resolution
Spectroscopy.

II. HH 204. The Astrophysical Journal, 2021; 918 (1): 27 DOI:
10.3847/ 1538-4357/ac0cf5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210902125022.htm

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