Magnetically Confined Interstellar Hot Plasma in the Nuclear Bulge of Our Galaxy

Nishiyama, Shogo; Yasui, Kenji; Nagata, T.; Yoshikawa, Tetsuro; Uchiyama, Hideki; Schödel, R.; Hatano, Hitoshi; Sato, Shuji; Sugitani, Koji; Suenaga, Takuya; Kwon, Jungmi; Tamura, Motohide

doi:10.1088/2041-8205/769/2/l28

Cited by 69 publications

(101 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These sizes are much larger than the observed NSD in the Milky Way. For example, the radial extent of the NSD in the Milky Way is around 230 pc (Launhardt, Zylka & Mezger 2002), and the vertical scale-height is measured to be around 45 pc (Nishiyama et al 2013). Note that the aim of this study is to explore the phenomenological link between the Galactic bar structure and the NSD.…”

Section: Bar-driven Growth Of Nuclear Bulgementioning

confidence: 97%

Age dating the Galactic bar with the nuclear stellar disc

Baba

Kawata

2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We perform an N-body/hydrodynamics simulation of an isolated Milky Way-like galaxy and demonstrate that the formation epoch of the galactic bar can be identified from the age distribution of the nuclear stellar disc (NSD). The bar formation triggers the gas inflow in the bar region, and the gas inflow reaches the central subkpc region followed by an intense star formation for ∼ 1 Gyr. The star formation in the central sub-kpc region forms the thinner, kinematically cooler and rotating NSD component. Consequently, the formation epoch of the galactic bar becomes the oldest limit of the NSD stellar populations, which tells us the formation epoch of the bar. We also discuss that a challenge to measure the age distribution of the NSD in the Milky Way is contamination from the other stellar components, such as a classical bulge component, whose contamination may not be negligible in the central region. We demonstrate that transverse velocities of tracer stars, which will be measured by the near-infrared space astrometry mission, JASMINE, are crucial to kinematically distinguish the NSD from the other stellar component.

show abstract

Section: Bar-driven Growth Of Nuclear Bulgementioning

confidence: 97%

Age dating the Galactic bar with the nuclear stellar disc

Baba

Kawata

2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…We apply the term "background" to both foreground and background contributions that contaminate our sample. We use the stellar density map of the central 6 • × 2 • of our Galaxy from Nishiyama et al (2013) to model the GB and NSD in order to subtract them from the data and isolate the NSC in the stellar density maps (see left panel in Fig. 7).…”

Section: Structure Of the Nuclear Stellar Clustermentioning

confidence: 99%

New constraints on the structure of the nuclear stellar cluster of the Milky Way from star counts and MIR imaging

Gallego-Cano

Schödel

Nogueras-Lara

et al. 2020

A&A

View full text Add to dashboard Cite

Context. The Milky Way nuclear star cluster (MWNSC) is a crucial laboratory for studying the galactic nuclei of other galaxies, but its properties have not been determined unambiguously until now. Aims. We aim to study the size and spatial structure of the MWNSC. Methods. This study uses data and methods that address potential shortcomings of previous studies on the topic. We use 0.2 angular resolution K s data to create a stellar density map in the central 86.4pc x 21pc at the Galactic center. We include data from selected adaptive-optics-assisted images obtained for the inner parsecs. In addition, we use IRAC/Spitzer mid-infrared (MIR) images. We model the Galactic bulge and the nuclear stellar disk in order to subtract them from the MWNSC. Finally, we fit a Sérsic model to the MWNSC and investigate its symmetry. Results. Our results are consistent with previous work. The MWNSC is flattened with an axis ratio of q = 0.71 ± 0.10, an effective radius of R e = (5.1 ± 1.0) pc, and a Sérsic index of n = 2.2 ± 0.7. Its major axis may be tilted out of the Galactic plane by up to −10 degrees. The distribution of the giants brighter than the Red Clump (RC) is found to be significantly flatter than the distribution of the faint stars. We investigate the 3D structure of the central stellar cusp using our results on the MWNSC structure on large scales to constrain the deprojection of the measured stellar surface number density, obtaining a value of the 3D inner power law of γ = 1.38 ± 0.06 sys ± 0.01 stat . Conclusions. The MWNSC shares its main properties with other extragalactic NSCs found in spiral galaxies. The differences in the structure between bright giants and RC stars might be related to the existence of not completely mixed populations of different ages. This may hint at recent growth of the MWNSC through star formation or cluster accretion.

show abstract

“…In this paper we use J, H and K s photometry of three fields. A control field (from now on F0), centred on SgrA* (17 h 45 m 40.1 s , -29 • 00 ′ 28 ′′ ) and two fields in the bulge (F1 and F2) located ∼0.6 • and ∼0.4 • to Galactic North, outside of the Nuclear Bulge (NB) of the Galaxy (Launhardt et al 2002;Nishiyama et al 2013), with center coordinates 17 h 43 m 11.6 s , -28 • 41 ′ 54 ′′ and 17 h 43 m 53.8 s , -28 • 48 ′ 07 ′′ . The approximate size of the fields is 7.95 ′ × 3.43 ′ .…”

Section: Datamentioning

confidence: 99%

Star formation history and metallicity in the Galactic inner bulge revealed by the red giant branch bump

Nogueras-Lara

Schödel

Dong

et al. 2018

A&A

View full text Add to dashboard Cite

Context. The study of the inner region of the Milky Way's bulge is hampered by high interstellar extinction and extreme source crowding. Sensitive high angular resolution near-infrared imaging is needed to study stellar populations and their characteristics in such a dense and complex environment. Aims. We aim at investigating the stellar population in the innermost Galactic bulge, to study the star formation history in this region of the Galaxy. Methods. We use the 0.2 ′′ angular resolution JHK s data from the GALACTICNUCLEUS survey to study the stellar population within two 8.0 ′ × 3.4 ′ fields, about 0.6 • and 0.4 • to the Galactic north of the Milky Way's centre and to compare it with the one in the immediate surroundings of Sagittarius A*. We also characterise the absolute extinction and the extinction curve of the two fields. Results. The average interstellar extinction to the outer and the inner field is A Ks ∼ 1.20±0.08 mag and ∼ 1.48±0.10 mag, respectively. We present K s luminosity functions that are complete down to at least 2 magnitudes below the red clump (RC). We detect a feature in the luminosity functions that is fainter than the RC by 0.80 ± 0.03 and 0.79 ± 0.02 mag, respectively, in the K s -band. It runs parallel to the reddening vector. We identify the feature as the red giant branch bump. Fitting α-enhanced BaSTI luminosity functions to our data, we find that a single old stellar population of ∼ 12.8 ± 0.6 Gyr and Z = 0.040 ± 0.003 provides the best fit. Our findings thus show that the stellar population in the innermost bulge is old, similar to the one at larger distances from the Galactic plane, and that its metallicity increases down to distances as short as about 60 pc from the centre of the Milky Way. Comparing the obtained metallicity with previous known values at larger latitudes (|b| > 2 • ), our results favour a flattening of the gradient at |b| < 2 • . As a secondary result we obtain that the extinction index in the studied regions agrees within the uncertainties with the value of α = 2.30 ± 0.08, derived in Nogueras-Lara et al. (2018) for the very Galactic centre. Conclusions.

show abstract

Magnetically Confined Interstellar Hot Plasma in the Nuclear Bulge of Our Galaxy

Cited by 69 publications

References 48 publications

Age dating the Galactic bar with the nuclear stellar disc

Age dating the Galactic bar with the nuclear stellar disc

New constraints on the structure of the nuclear stellar cluster of the Milky Way from star counts and MIR imaging

Star formation history and metallicity in the Galactic inner bulge revealed by the red giant branch bump

Contact Info

Product

Resources

About