NGC 5018 Galaxy Group: Astronomers Unveil Intra-Group Globular Cluster System

Introduction to the Study of NGC 5018 and Its Globular Clusters

Astronomers using VLT Survey Telescope to study globular clusters in the NGC 5018 galaxy group, revealing important stellar evolution insights.

Astronomers from Italy and Germany utilized the VLT Survey Telescope (VST) to investigate the galaxy group NGC 5018. Findings from this research, shared on arXiv on December 23, reveal valuable details about the group's globular cluster system.

What Are Globular Clusters Why Are They Important?

Globular clusters (GCs), composed of densely packed stars orbiting galaxies, serve as natural laboratories for studying stellar and galactic evolution. These clusters, closely associated with episodes of intense star formation, hold key insights into the formation and development of early-type galaxies. Additionally, GCs provide valuable data on interaction events within their host galaxies and the larger galaxy group.

The NGC 5018 Galaxy Group: Key Members and Composition

NGC 5018: The Luminous Elliptical Galaxy

The NGC 5018 galaxy group derives its name from its most luminous member, NGC 5018, a massive elliptical galaxy located approximately 132.5 million light-years away in the Virgo constellation.

Other Prominent Member of NGC 5018

Other prominent members of this group include the edge-on spiral NGC 5022, the face-on spiral NGC 5006, and two lenticular galaxies, MCG-03-34-013 and PGC140148.

Earlier Research on Globular Clusters in NGC 5018

Earlier research has identified two distinct sub-populations of globular clusters (GCs) in the galaxy NGC 5018: a smaller group of younger GCs aged several hundred million to six billion years, and a larger group of older GCs.

In-Depth Investigation into NGC 5018's GC System

Research Team and Methodology

A research team, headed by Pratik Lonare from the Abruzzo Astronomical Observatory in Teramo, Italy, has undertaken a deeper investigation into both the globular cluster system of NGC 5018 and the entire galaxy group.

Deep Imaging with VST and VEGAS

According to the researchers, "This work employs deep, multi-band, wide-field imaging of the NGC 5018 galaxy group gathered with the VLT Survey Telescope (VST) during the VST Elliptical Galaxy Survey (VEGAS), and we conduct a thorough investigation of its GC system."

Discovering the Intra-Group Globular Cluster System

Thanks to VEGAS imaging data, Lonare's team was able to pinpoint globular cluster candidates throughout the NGC 5018 galaxy group, unveiling the existence of an intra-group GC system. The 2D distribution map highlights a concentration of GC candidates in NGC 5018, while no notable GC concentrations are detected in the other group members.

Radial and Color Profile Analysis of Globular Clusters

Radial Density Profile

Overall, the radial density profile of globular cluster candidates in NGC 5018 mirrors the surface brightness profile of the galaxy. The color profile of these candidates exhibits a dominant component, peaking around 0.75 mag.

Spatial Distribution and Color profile

The observations revealed that the intra-group globular cluster population is distributed along the five bright galaxies and encircles the NGC 5018 group. This spatial arrangement corresponds with the intra-group light (IGL) detected in the group, but extends to greater from the group's center.

Blue and Red Globular Cluster Components in the Intra-Group System

The analysis of the color profile of intra-group globular cluster candidates indicates the existence of both blue and red GC components, with peaks at approximately 0.45 and 0.80 mag, respectively. The blue GC component is observed to be more spatially extended than the red GC component relative to NGC 5018.

Conclusion: Dispersal of Blue Globular Clusters

"The combination of these findings with previous studies on the intra-group light (IGL) leads to the hypothesis that part of the blue GC population in the intra-grou p region may have once been part of NGC 5018, subsequently dispersed by tidal forces from neighbouring galaxies," the authors conclude.

Number of Globular Cluster Candidates in NGC 5018

The astronomers note that the total numbers of globular cluster candidates across the entire NGC 5018 group is approximately 4,000, with NGC 5018 itself hosting estimated 485 candidates.

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Labels: Astronomy Research, Galaxies, Globular Clusters, NGC5018, Stellar Evolution, VLT Survey Telescope

Gran 5 Cluster Hosts Dual Stellar Populations: A Recent Research

The seven spectroscopic target stars are marked by green circles.

Introduction: Unveiling Dual Stellar Populations in Gran 5

Astronomers utilizing the Gemini-South telescope have carried out high-resolution near-infrared spectroscopy on the stars of the Gran 5 Galactic Globular Cluster. Their research uncovered two separate stellar populations with differing metallicities. The findings were published on October 28 in a paper on arXiv.

Understanding Globular Clusters and Their Significance

What Are Globular Clusters?

Globular Clusters (GCs) are groupsof tightly bound stars that orbit galaxies, providing astronomers with valuable insights into stellar and galactic evolution. These clusters serve as natural laboratories, particularly aiding in the study of the formation and evolution of early-type galaxies, as their origins appear to be closely tied to phases of intense star formation.

Gran 5: A Low-Mass Globular Cluster

Gran 5 is a recently identified low-mass globular cluster, located approximately 14,600 light years from the Galactic center. With a mass of around 22,900 solar masses, it is believed to be an accreted object linked to the Gaia–Enceladus–Sausage kinematic structure in the Milky Way's halo.

Research Methodology: High-Resolution Spectroscopy

Studying Gran 5 with the IGRINS Spectrometer

To further understand the stellar populations of Gran 5 and uncover their detailed chemical properties, a team of astronomers, headed by Dongwook Lim from Yonsei University in Seoul, South Korea, studied seven stars within the cluster using the Immersion Grating Infrared Spectrometer (IGRINS).

The researchers reported in their paper, "High-resolution near-infrared spectroscopy was performed on seven stars in the Gran 5 field using IGRINS on the Gemini-South telescope."

Spectroscopy Results: Stellar Membership and Metallicity

From the spectroscopy of the seven stars, Lim's team determined that six were members of the cluster, while one star was excluded due to its markedly different radial velocity. The six cluster members exhibited heliocentric radial velocities of approximately -60 km/s and low metallicities around -0.65 dex, confirming Gran 5 as a genuine globular cluster.

Key Findings: Two Stellar Population in Gran 5

Distinct Metallicity Groups

The study, however, revealed that the stars examined can be separated into two groups based on metallicity, with mean values of -0.76 dex and -0.55 dex for each group. Since no correlation was observed between these groups and heliocentric radial velocities or atmospheric parameters, the astronomers suggest that Gran 5 contains two distinct stellar populations with different metallicities.

Gran 5's Chemo-Dynamical Properties

The authors of the paper highlight that their study represents the first detection of two stellar populations with distinct metallicities in a low-mass globular cluster. They also note that the chemo-dynamical properties of Gran 5 indicate it is not associated with the Gaia-Enceladus-Sausage structure, but rather belongs to the Galactic bulge or disk.

Conclusion: Implications for, Stellar Evolution and Cluster Formation

Metallicity Variation: A Sign of Different Formation Processes?

The researchers conclude that the metallicity variation observed in Gran 5 might be due to different formation processes or the cluster's loss of a substantial amount of mass throughout its evolution.