High-resolution MEGARA Integral-field Unit Spectroscopy and Structural Analysis of a Fast-rotating, Disky Bulge in NGC 7025

Dullo, Bililign T.; Chamorro-Cazorla, M.; Paz, A. Gil de; Castillo-Morales, A.; Gallego, J.; Carrasco, E.; Iglésias-Páramo, J.; Cedazo, R.; García-Vargas, M. L.; Pascual, S.; Cardiel, N.; Pérez-Calpena, A.; Gómez-Cambronero, Pedro; Martínez-Delgado, I.; Catalán-Torrecilla, C.

doi:10.3847/1538-4357/aaf424

Cited by 17 publications

(34 citation statements)

References 115 publications

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“…Therefore, these models would need to be convolved with the instrument spectral resolution to be adequately compared with data. This is indeed the case for our third case, the bulge of the galaxy NGC 7025, studied by Dullo et al (2019). This is an isolated unbarred Sa galaxy located at a distance D=67.3 Mpc with a bulge-to-total flux ratio (B/T) between 0.3 and 0.44, implying a stellar mass of ∼ 4.34 ± 1.70 10 10 M .…”

Section: Spectral Absorption Linessupporting

confidence: 68%

HR-pyPopStar: high wavelength-resolution stellar populations evolutionary synthesis model

Millán-Irigoyen,

Mollá,

Cerviño

et al. 2021

Preprint

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We present the HR-pyPopStar model, which provides a complete set (in ages) of high resolution (HR) Spectral Energy Distributions of Single Stellar Populations. The model uses the most recent high wavelength-resolution theoretical atmosphere libraries for main sequence, post-AGB/planetary nebulae and Wolf-Rayet stars. The Spectral Energy Distributions are given for more than a hundred ages ranging from 0.1 Myr to 13.8 Gyr, at four different values of the metallicity (Z = 0.004, 0.008, 0.019 and 0.05), considering four different IMFs. The wavelength range goes from 91 to 24 000 Å in linear steps δλ = 0.1 Å, giving a theoretical resolving power R th,5000 ∼ 50 000 at 5000 Å. This is the main novelty of these spectra, unique for their age and wavelength ranges. The models include the ionising stellar populations that are relevant both at young (massive hot stars) as well as old (planetary nebulae) ages. We have tested the results with some examples of HR spectra recently observed with MEGARA at GTC. We highlight the importance of wavelength-resolution in reproducing and interpreting the observational data from the last and forthcoming generations of astronomical instruments operating at 8-10m class telescopes, with higher spectral resolution than their predecessors.

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Section: Spectral Absorption Linessupporting

confidence: 68%

HR-pyPopStar: high wavelength-resolution stellar populations evolutionary synthesis model

Millán-Irigoyen,

Mollá,

Cerviño

et al. 2021

Preprint

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“…In preparation for the optimisation of the MEGADES survey, we carried out commissioning observations of NGC 7025 that were taken with all 18 MEGARA VPHs. After the initial analysis conducted by Dullo et al (2019), we decided for both this work and for the observations of the inner regions of the MEGADES sample to focus on the low spectral resolution (LR; R ∼ 6000) VPHs because they allow us to cover a wider spectral range with still good enough spectral resolution. In addition, the high central velocity dispersion of this galaxy, σ ∼ 250 km s −1 (Dullo et al 2019) limits the advantage (in terms of information content) of using MR and HR VPHs.…”

Section: Megara Spectroscopymentioning

confidence: 99%

“…After the initial analysis conducted by Dullo et al (2019), we decided for both this work and for the observations of the inner regions of the MEGADES sample to focus on the low spectral resolution (LR; R ∼ 6000) VPHs because they allow us to cover a wider spectral range with still good enough spectral resolution. In addition, the high central velocity dispersion of this galaxy, σ ∼ 250 km s −1 (Dullo et al 2019) limits the advantage (in terms of information content) of using MR and HR VPHs. For the study of the disks of the MEGADES sample, especially for low-inclination galaxies, we might have to also rely on medium (MR; R ∼ 12 000) and high-resolution (HR; R ∼ 20 000) data.…”

Section: Megara Spectroscopymentioning

confidence: 99%

“…Along with its isophotal twist, this caused Barrera-Ballesteros et al (2015) to classify this object as a merger remnant. The photometric and kinematic analyses by Dullo et al (2019) have shown that the bulge is a fast rotator with a low Sérsic index n ∼ 1.80. However, a detailed stellar population analysis of the bulge is crucial if we are to properly understand this galaxy's formation.…”

Section: Introductionmentioning

confidence: 99%

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Stellar populations with MEGARA: The inner regions of NGC 7025

Chamorro-Cazorla

Paz

Castillo-Morales

et al. 2022

A&A

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Context. This paper aims to determine the capabilities of the MEGARA spectrograph at the Gran Telescopio Canarias (GTC), which is an optical integral-field unit, for studying stellar populations. We also aim to exploit its combination of high spectral (R ∼ 6000, 12 000 and 20 000) and spatial (0.62″) resolution within its 12″.5 × 11″.3 field of view. We do this by analysing the commissioning data of the nearby S0a galaxy NGC 7025. Aims. We establish a systematic method through which we can determine the properties of the stellar populations in the observations made with MEGARA, more specifically, within the MEGADES legacy project. For this paper in particular, we determine the properties of the stellar populations of NGC 7025. Methods. We used MEGARA observations of galaxy NGC 7025 that were taken during the commissioning phase of the instrument. We applied different approaches to estimate the properties of the stellar populations with the highest possible certainty. In addition to the specific study of NGC 7025 and in the context of the MEGADES survey, we have carried out a number of tests to determine the expected errors (including potential biases) in these star formation history (SFH) derivations as a function of these parameters, namely spectral setup, signal-to-noise ratio, σ, and the SFH itself. Results. All the studies we conduct (both full spectral fitting and absorption line indices) of the stellar populations of NGC 7025 indicate that the stars that form its bulge have supersolar metallicity and considerably old ages (∼10 Gyr) in general. Using three different combinations of MEGARA spectral setups, we determined that the bulge of NGC 7025 has smild negative mass-weighted age gradient. For the more detailed SFH, our results indicate that in addition to a rather constant star formation at early epochs, a peak in the formation history of the stars in the bulge is also found 3.5–4.5 Gyr ago. This partly explains the mass-weighted age gradients we measured. Conclusions. The scenario presented in NGC 7025 is that of an isolated galaxy under secular evolution that about 3.5–4.5 Gyr ago likely experienced a minor merger (mass ratio 1/10) that induced an increase in star formation and also perturbed the morphology of its outer disc. In addition to these specific results for NGC 7025, we report different lessons learned for the ongoing exploitation of the MEGADES survey with the GTC, such as the need to obtain combined observations in the LR-B + LR-V setups and a signal-to-noise ratio of at least 20 per Å.

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“…MEGARA started the operation in 2017 and during the commissioning run the NGC 7469 galaxy has been observed among others (e.g. NGC 7025 Dullo et al 2019 andUGC 10205 Catalán-Torrecilla et al 2019). NGC 7469 (IRAS 23007+0836, MRK 1514) is a well studied active galaxy in the local Universe (z = 0.016317).…”

Section: Introductionmentioning

confidence: 99%

NGC 7469 as seen by MEGARA: new results from high-resolution IFU spectroscopy

Cazzoli

Paz

Márquez

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present our analysis of high-resolution (R ∼ 20 000) GTC/MEGARA integral-field unit spectroscopic observations, obtained during the commissioning run, in the inner region (12.5 arcsec × 11.3 arcsec) of the active galaxy NGC 7469, at spatial scales of 0.62 arcsec. We explore the kinematics, dynamics, ionisation mechanisms and oxygen abundances of the ionised gas, by modelling the Hα-[N II] emission lines at high signal-to-noise (> 15) with multiple Gaussian components. MEGARA observations reveal, for the first time for NGC 7469, the presence of a very thin (20 pc) ionised gas disc supported by rotation (V/σ = 4.3), embedded in a thicker (222 pc), dynamically hotter (V/σ = 1.3) one. These discs nearly co-rotate with similar peak-to-peak velocities (163 vs. 137 km s −1 ), but with different average velocity dispersion (38 ± 1 vs. 108 ± 4 km s −1 ). The kinematics of both discs could be possibly perturbed by star-forming regions. We interpret the morphology and the kinematics of a third (broader) component (σ > 250 km s −1 ) as suggestive of the presence of non-rotational turbulent motions possibly associated either to an outflow or to the lense. For the narrow component, the [N II]/Hα ratios point to the star-formation as the dominant mechanism of ionisation, being consistent with ionisation from shocks in the case of the intermediate component. All components have roughly solar metallicity. In the nuclear region of NGC 7469, at r ≤ 1.85 arcsec, a very broad (FWHM = 2590 km s −1 ) Hα component is contributing (41 per cent) to the global Hα-[N II] profile, being originated in the (unresolved) broad line region of the Seyfert 1.5 nucleus of NGC 7469.

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High-resolution MEGARA Integral-field Unit Spectroscopy and Structural Analysis of a Fast-rotating, Disky Bulge in NGC 7025

Cited by 17 publications

References 115 publications

HR-pyPopStar: high wavelength-resolution stellar populations evolutionary synthesis model

HR-pyPopStar: high wavelength-resolution stellar populations evolutionary synthesis model

Stellar populations with MEGARA: The inner regions of NGC 7025

NGC 7469 as seen by MEGARA: new results from high-resolution IFU spectroscopy

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