Astrophysics of Galaxies (astro-ph.GA)

Abstract: Protostellar outflows and jets are almost ubiquitous characteristics during the mass accretion phase, and encode the history of stellar accretion, complex-organic molecule (COM) formation, and planet formation. Episodic jets are likely connected to episodic accretion through the disk. Despite the importance, there is a lack of studies of a statistically significant sample of protostars via high-sensitivity and high-resolution observations. To explore episodic accretion mechanisms and the chronologies of episodic events, we investigated 42 fields containing protostars with ALMA observations of CO, SiO, and 1.3\,mm continuum emission. We detected SiO emission in 21 fields, where 19 sources are driving confirmed molecular jets with high abundances of SiO. Jet velocities, mass-loss rates, mass-accretion rates, and periods of accretion events are found to be dependent on the driving forces of the jet (e.g., bolometric luminosity, envelope mass). Next, velocities and mass-loss rates are positively correlated with the surrounding envelope mass, suggesting that the presence of high mass around protostars increases the ejection-accretion activity. We determine mean periods of ejection events of 20$-$175 years for our sample, which could be associated with perturbation zones of $\sim$ 2$-$25\,au extent around the protostars. Also, mean ejection periods are anti-correlated with the envelope mass, where high-accretion rates may trigger more frequent ejection events. The observed periods of outburst/ejection are much shorter than the freeze-out time scale of the simplest COMs like CH$_3$OH, suggesting that episodic events largely maintain the ice-gas balance inside and around the snowline.

Abstract: In this study, the structural and basic astrophysical parameters of the poorly studied open cluster Berkeley 6 are calculated. Analyses of the cluster are carried out using the third photometric, spectroscopic, and astrometric data release of Gaia (Gaia DR3). The membership probabilities of stars located in the direction of the cluster region are calculated by considering their astrometric data. Thus, we identified 119 physical members for Berkeley 6. The colour excess, distance, and age of the cluster are determined simultaneously on the colour-magnitude diagram. We fitted solar metallicity PARSEC isochrones to the colour-magnitude diagram by considering the most probable member stars and obtained $E(G_{\rm BP}-G_{\rm RP})$ colour excess as 0.918$\pm$0.145 mag. The distance and age of the cluster are determined as $d=2625\pm337$ pc and $t=350\pm50$ Myr, respectively.

Abstract: In the context of a project aimed at characterizing the dynamical evolution of old globular clusters in the Large Magellanic Cloud, we have secured deep HST/WFC3 images of the massive cluster NGC 1835. In the field of view of the acquired images, at a projected angular separation of approximately 2 arcmin from the cluster, we detected the small stellar system KMK88-10. The observations provided the deepest color-magnitude diagram ever obtained for this cluster, revealing that it hosts a young stellar population with an age of 600-1000 Myr. The cluster surface brightness profile is nicely reproduced by a King model with a core radius rc = 4 arcsec (0.97 pc), an half-mass radius rhm = 12 arcsec (2.9 pc), and a concentration parameter c~1.3 corresponding to a truncation radius rt~81 arcsec (19.5 pc). We also derived its integrated absolute magnitude (MV=-0.71) and total mass (M~80-160 Msun). The most intriguing feature emerging from this analysis is that KMK88-10 presents a structure elongated in the direction of NGC 1835, with an intracluster over-density that suggests the presence of a tidal bridge between the two systems. If confirmed, this would be the first evidence of a tidal capture of a small star cluster by a massive globular.

Abstract: The ratio of the H$\alpha$ and radio continuum intensities in the North Polar Spur (NPS) is measured to be $\lesssim 50$, two orders of magnitude smaller than the values observed in the typical shell-type old supernova remnants (SNRs), Cygnus Loop and S147, of $\sim 10^4$.The extremely low} H$\alpha$-to-radio intensity ratio favors the GC explosion model}, which postulates a giant shock wave in the hot and low-density Galactic halo with low hydrogen recombination rate, over the local supernova(e) remnant model.

Abstract: The hierarchical structure formation paradigm predicts the formation of pairs of supermassive black holes in merging galaxies. When both (or one) members of the SMBH pair are unobscured AGNs, the system can be identified as a dual (or offset) AGN. Quantifying the abundance of these AGN pairs as functions of separation, redshift and host properties is crucial to understanding SMBH formation and AGN fueling in the broad context of galaxy formation. The High Latitude Wide Area Survey with Roman, with its unprecedented combination of sensitivity, spatial resolution, area and NIR wavelength coverage, will revolutionize the study of galactic-scale environments of SMBH pairs. This white paper summarizes the science opportunities and technical requirements on the discovery and characterization of SMBH pairs down to galactic scales (i.e., less than tens of kpc) over broad ranges of redshift (1<z<7) and luminosity (Lbol>1E42 erg/s).

Abstract: The Stellar Abundances and Galactic Evolution Survey (SAGES) of the northern sky is a specifically-designed multi-band photometric survey aiming to provide reliable stellar parameters with accuracy comparable to those from low-resolution optical spectra. It was carried out with the 2.3-m Bok telescope of Steward Observatory and three other telescopes. The observations in the $u_s$ and $v_s$ passband produced over 36,092 frames of images in total, covering a sky area of $\sim9960$ degree$^2$. The median survey completeness of all observing fields for the two bands are of $u_{\rm s}=20.4$ mag and $v_s=20.3$ mag, respectively, while the limiting magnitudes with signal-to-noise ratio (S/N) of 100 are $u_s\sim17$ mag and $v_s\sim18$ mag, correspondingly. We combined our catalog with the data release 1 (DR1) of the first of Panoramic Survey Telescope And Rapid Response System (Pan-STARRS1, PS1) catalog, and obtained a total of 48,553,987 sources which have at least one photometric measurement in each of the SAGES $u_s$ and $v_s$ and PS1 $grizy$ passbands, which is the DR1 of SAGES and it will be released in our paper. We compare our $gri$ point-source photometry with those of PS1 and found an RMS scatter of $\sim2$% in difference of PS1 and SAGES for the same band. We estimated an internal photometric precision of SAGES to be on the order of $\sim1$%. Astrometric precision is better than $0^{\prime\prime}.2$ based on comparison with the DR1 of Gaia mission. In this paper, we also describe the final end-user database, and provide some science applications.