Utilizing the Hubble Area Telescope (HST), astronomers have investigated the stellar inhabitants of the globular cluster NGC 1835. They detected a remarkably prolonged horizontal department on this system. The invention, reported February 28 on the preprint server arXiv, marks the primary time when such a characteristic is present in a globular cluster past our Milky Way galaxy.
Globular clusters (GCs) are collections of tightly certain stars orbiting galaxies. Astronomers understand them as pure laboratories enabling research on the evolution of stars and galaxies. Particularly, globular clusters may assist researchers to higher perceive the formation historical past and evolution of early-type galaxies, because the origin of GCs appears to be intently linked to durations of intense star formation.
NGC 1835 is an previous and large globular cluster situated near the central bar of the Giant Magellanic Cloud (LMC). The cluster is estimated to be about 13 billion years previous and its mass is most probably at a stage of 600,000 solar plenty.
Not too long ago, a group of astronomers led by Camilla Giusti of the College of Bologna in Italy, has inspected the stellar inhabitants of NGC 1835 as a part of the continued analysis program finding out the properties of previous LMC clusters. For this function, they used optical and close to ultraviolet photographs obtained with HST.
“Within the framework of a challenge geared toward performing a brand new characterization of the oldest and most compact stellar techniques within the LMC, we’ve introduced an in depth multi-wavelength photometric examine of the GC NGC 1835,” the researchers wrote within the paper.
By analyzing the collected knowledge, Giusti’s group has recognized the presence of a really prolonged blue tail of the horizontal department (HB). Typically, HB is a grouping of stars on the Hertzsprung-Russell (H-R) diagram that varieties a horizontal line on this diagram, main away from the red-giant department (RGB). These stars have handed by means of the RGB and have begun helium fusion within the core, with a surrounding shell of hydrogen fusion.
The prolonged HB in NGC 1835 seems to span greater than 4.5 magnitudes in each magnitude (within the near-ultraviolet and optical bands) and shade from the area redder than the instability strip, overlaying efficient temperatures from 5,000 to 30,000 Ok. It was discovered that the HB on this cluster consists of a big inhabitants of RR Lyrae variables—67 confirmed and 52 new candidates.
The astronomers underlined that such an prolonged blue tail of the HB has been noticed in only some circumstances in our galaxy, together with GCs like M3 and M13. Nonetheless, such a characteristic has by no means been detected earlier than in an extra-galactic cluster.
By evaluating the HB in NGC 1835 with different GCs, it was discovered that it’s a mixture of HBs in M3 and M13. In line with the paper, the morphology of the HB in NGC 1835 showcases a placing similarity compared with the HB in M13, which means that the investigated GC might also host a inhabitants of slowly cooling white dwarfs—like M13.
Extra data:
Camilla Giusti et al, Discovery of an prolonged Horizontal Department within the Giant Magellanic Cloud globular cluster NGC1835, arXiv (2024). DOI: 10.48550/arxiv.2402.18389
Journal data:
arXiv
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Prolonged horizontal department detected in globular cluster NGC 1835 (2024, March 6)
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