Massive star population of the Virgo Cluster galaxy NGC4535

Abstract

We analyzed the massive star population of the Virgo Cluster galaxy NGC 4535 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in filters F555W and F814W, equivalent to Johnson V and Kron-Cousins I. We performed high precision point spread function fitting photometry of 24353 sources including 3762 candidate blue supergiants, 841 candidate yellow supergiants, and 370 candidate red supergiants. We estimated the ratio of blue to red supergiants as a decreasing function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics (MESA) isochrones at solar metallicity, we defined the luminosity function and estimated the star formation history of the galaxy over the last 60 Myr. We conducted a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range, and the inverse von-Neumann ratio. This analysis yielded 120 new variable candidates with absolute magnitudes ranging from MV = −4 to −11 mag. We used the MESA evolutionary tracks at solar metallicity to classify the variables based on their absolute magnitude and their position on the color-magnitude diagram. Among the new candidate variable sources are eight candidate variable red supergiants, three candidate variable yellow supergiants and one candidate luminous blue variable, which we suggest for follow-up observations.

A Census of B[e] Supergiants

“…[156] (10584-9-1) 9:55:18.97 +69:08:27. 54 19.10 [156] In the past few years, additional surveys have been performed, using large ground-based facilities (e.g., [157]) and space telescopes (e.g., [158,159]). These surveys were aimed at revealing the luminous and variable massive star populations of other galaxies even further away.…”

Discrete star formation events in the central bar of the Small Magellanic Cloud

“…The method is applied to MS stars and it is useful for studying the relatively recent SFH, as the time resolution and accuracy degrade with increasing look-back time. The same method was recently applied by Spetsieri et al (2018) to probe the SFH of massive stars in a Virgo cluster galaxy. To derive the SFRs, we follow exactly the same procedures and assumptions described in Dohm-Palmer et al (1997), on completeness-corrected MS stars.…”

Transient variability and variability of massive stars with the Hubble space telescope

“…Variability studies on YSG stars were previously conducted by Dorn-Wallenstein et al (2019); Spetsieri et al (2018); Kourniotis et al (2014b); Gordon et al (2016). Recently Dorn-Wallenstein et al (2019) suggested that variability in the YSG phase could be the best way to the best or most unambiguous way of distinguishing between rightward-and leftward-moving YSGs.…”

“…Consequently, any meaningful period determination may require decades of observations. HST observations available in the archive provide a wide variety of observations of nearby galaxies over a large time-baseline that have been studies for variability (Spetsieri et al 2018;Yang et al 2018).…”

“…;Percy & Kim (2014);Humphreys et al (2016);Kourniotis et al (2017);Spetsieri et al (2018), in the region with M ⊙ ≥ 20 M ⊙ and log L/L o > 5.4. and is typical of amplitude 0.3-0.6 magnitudes. As spectroscopic classification is essential for accurate discrimination between YHGs and YSGs, we cannot further comment on the state of our yellow stars.…”