J/A+A/710/A246 NGC 346 VIHa photometry (Dik+, 2026)
Photometric determination of the mass accretion rates of pre-main sequence
stars. IX. Recent star formation in the periphery of NGC 346.
Dik C., De Marchi G.
<Astron. Astrophys. 710, A246 (2026)>
=2026A&A...710A.246D 2026A&A...710A.246D (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Photometry, H-alpha ;
Optical
Keywords: stars: formation - stars: pre-main sequence - Magellanic Clouds -
galaxies: star clusters: individual: NGC 346
Abstract:
We studied the properties of star formation and the characteristics of
young stars in a quiet region located beyond the outskirts of the
prominent star-forming cluster NGC 346 in the Small Magellanic Cloud
(SMC). Utilising observations from the Hubble Space Telescope across
the broad V and I bands, as well as the narrow Halpha band, we
identified populations with ages of roughly 10, 60, 400Myr and of 5Gyr
through isochrone comparison. We successfully identified 137 bona fide
pre-main sequence (PMS) candidates exhibiting Halpha excess with a
significance level of 5 sigma, accompanied by a Halpha line emission
equivalent width exceeding 20Å. Physical parameters for these PMS
stars were determined, including mass, age, accretion luminosity, and
mass accretion rate. Most PMS stars have an age around 16 Myr and an
average mass of 0.80±0.16M{sun{. The median mass accretion rate
for all 137 PMS stars is estimated to be about 8.0x10-9M☉/yr.
While this rate is lower than that observed in the NGC 346 cluster
itself, it is comparable with those measured for PMS stars in
low-density star-forming regions in the SMC, despite the absence of
apparent clustering and nebulosity. Furthermore, our analysis reveals
that the ratios of accreting and non-accreting PMS stars to non-PMS
stars and their mass accretion rate correlate with their distance from
a group of hot massive stars in the vicinity. This suggests that the
ultraviolet radiation emitted by these massive stars might erode the
circumstellar discs of nearby PMS stars. Lastly, the overlap between
our studied region and observations from the James Webb Space
Telescope reveals that some of the identified PMS stars display
near-infrared excess.
Description:
This table provides the catalogue of 12649 sources with good
photometry detected in a field located about 9 arcmin south of the
centre of the NGC 346 cluster in the Small Magellanic Clouds. Besides
the identification number and coordinates of the stars (RA and DEC in
decimal degree), the table contains for each source the magnitudes and
uncertainties measured in the following bands: V (HST/ACS/WFC F555W),
I (HST/ACS/WFC F814W), and Halpha (HST/WFC3/F656N).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 67 12649 Photometric catalogue for 12649 good sources
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [1/12649] Identification number
8- 16 F9.6 deg RAdeg Right ascension (J2000)
19- 28 F10.6 deg DEdeg Declination (J2000)
31- 35 F5.2 mag Vmag Magnitude in V band (F555W)
38- 41 F4.2 mag e_Vmag Uncertainty of magnitude in V band (F555W)
44- 48 F5.2 mag Imag Magnitude in I band (F814W)
51- 54 F4.2 mag e_Imag Uncertainty of magnitude in I band (F814W)
57- 61 F5.2 mag Hamag Magnitude in Halpha band (F656N)
64- 67 F4.2 mag e_Hamag Uncertainty of magnitude in Halpha band (F656N)
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Acknowledgements:
Guido De Marchi, gdemarchi(at)esa.int
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 13-May-2026