J/A+A/684/A157 Spectra of stellar stream with MEGARA (Martinez-Delgado+, 2024)
Once in a blue stream.
Detection of recent star formation in the NGC 7241 stellar stream with MEGARA.
Martinez-Delgado D., Roca-Fabrega S., Gil de Paz A., Erkal D.,
Miro-Carretero J., Makarov D., Voggel K.T., Leaman R., Bolchin W.,
Pearson S., Donatiello G., Rubtsov E., Akhlaghi M., Gomez-Flechoso M.A.,
Raji S., Lang D., Block A., Gallego J., Carrasco E., Garcia-Vargas M.L.,
Iglesias-Paramo J., Pascual S., Cardiel N., Perez-Calpena A.,
Castillo-Morales A., Gomez-Alvarez P.
<Astron. Astrophys. 684, A157 (2024)>
=2024A&A...684A.157M 2024A&A...684A.157M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Spectra, optical
Keywords: galaxies: dwarf - galaxies: formation - galaxies: interaction
Abstract:
In this work we study the striking case of a narrow blue stream with a
possible globular cluster-like progenitor around the NGC 7241 galaxy
and its foreground dwarf companion. We want to figure out if the
stream was generated by tidal interaction with NGC 7241 or if it first
interacted with the foreground dwarf companion and later both fell
together toward NGC 7241.
We used four sets of observations, including a follow-up spectroscopic
study of this stream based on data taken with the MEGARA instrument at
the 10.4m Gran Telescopio Canarias using the integral field
spectroscopy mode, the Mount Lemmon 0.80m telescope, the Telescopio
Nazionale Galileo, the DESI Imaging Legacy surveys, and GALEX archival
data. We also used high-resolution zoomed-in cosmological simulations.
Our data suggest that the compact object we detected in the stream is
a foreground Milky Way halo star. Near this compact object we detect
emission lines overlapping a less compact, bluer, and fainter blob of
the stream that is clearly visible in both ultraviolet and optical
deep images. From its heliocentric systemic radial velocity derived
from the [OIII]λ5000Å lines (Vsyst=1548.58±1.80km/s) and
new UV and optical broadband photometry, we conclude that this
overdensity could be the actual core of the stream, with an absolute
magnitude of Mg~-10 and a g-r=0.08±0.11, consistent with a remnant
of a low-mass dwarf satellite undergoing a current episode of star
formation. From the width of the stream and assuming a circular orbit,
we calculate that the progenitor mass can be typical of a dwarf
galaxy, but it could also be substantially lower if the stream is on a
very radial orbit or if it was created by tidal interaction with the
companion dwarf instead of with NGC 7241. These estimates also suggest
that this is one of the lowest mass streams detected to date beyond
the Local Group. Finally, we find that blue stellar streams containing
star formation regions are commonly predicted by high-resolution
cosmological simulations of galaxies lighter than the Milky Way. This
scenario is consistent with the processes explaining the bursty star
formation history of some dwarf satellites, which are followed by a
gas depletion and a fast quenching once they enter within the virial
radius of their host galaxies for the first time. Thus, it is likely
that the stream's progenitor is undergoing a star formation burst
comparable to those that have shaped the star formation history of
several Local Group dwarfs in the last few gigayears.
Description:
The brightest region of the NGC 7241 stream was observed with the
Multi Espectrografo en GTC de Alta Resolucion para Astronomia
(MEGARA) instrument at the Gran Telescopio Canarias (GTC) on the night
of June 6, 2020, using the Integral Field Unit (IFU) in the LR-B
spectral configuration with a power resolution of R∼5000 in
the wavelength interval 4332-5199Å, for a total exposure time of
3600s.
Reduced MEGARA spectra.
Objects:
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RA (2000) DE Designation(s)
----------------------------------------------------
22 15 49.87 +19 13 56.4 NGC 7241 = MCG+03-56-020
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 124 2 List of fits spectra
fits/* . 2 Individual fits spectra
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Nx Number of pixels along X-axis
6- 27 A22 "datime" Obs.date Observation date
29- 32 I4 0.1nm blambda Lower value of wavelength interval
34- 40 F7.2 0.1nm Blambda Upper value of wavelength interval
42- 45 F4.2 0.1nm dlambda Wavelenght resolution
47- 48 I2 Kibyte size Size of FITS file
50- 85 A36 --- FileName Name of FITS file, in subdirectory fits
87-124 A38 --- Title Title of the FITS file
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Acknowledgements:
David Martinez-Delgado, dmartinez(at)iaa.es
(End) Patricia Vannier [CDS] 18-Jan-2024