Young stars in the disk of M82

We present CCD VI_C photometry in a field 1.9 − 1.3 square arcmin and positioned about 3 arcmin north-east of the centre of M82. More than 100 stars have been identified and measured above the photometric limits V = 23^m.5, I = 22^m. Most of the objects fainter than V ≈︁ 20^m should be members of M82 as expected from the statistics of foreground stars. Starlike as well as 2–3 somewhat diffuse objects - candidates of globular clusters - preferentially occupy yellow colours in the colour-magnitude diagram; extreme blue and red objects are missing. The colour-magnitude diagram indicates continuing star formation in this part of the disk. The absence of blue stars is caused by reddening; no convincing explanation is found for the missing red supergiants. Young stars are distributed throughout the whole field, the youngest being concentrated in associations at the SW edge of the field. To cope with the very irregular background created by the galaxy' s main body and with the low contrast of many of the stars against this background, a modified photometric method is introduced in which the background is estimated using the intensities in a ring drawn very tightly around the star in the wings of the point spread function.     

Estimates of Trends of Climatically Important Atmospheric Gases Near St. Petersburg

Izvestiya, Atmospheric and Oceanic Physics - Total column amounts (TCAs) of various climatically important atmospheric gases have been determined in Peterhof for the period between 2009 and 2018....     

The central region of NGC 3077: ground‐based photometry and age of bright ‘starlike’ objects

We present UBVI_C photometry of starlike objects in the central region of NGC 3077. The colour‐colour and colour‐magnitude diagrams of the objects are discussed. Many of the objects under consideration, starlike from the ground, are probably dense young star clusters (super star clusters, SSC). Ages spreading over ∼4 to ∼150 Myr are estimated for most of these objects. Sakai and Madore (2001) found enhanced star formation ∼30–125 Myr ago also in the halo of this galaxy; thus, high star forming activity has occurred within the entire galaxy (centre and halo) since ∼130…150 Myr. Having ended in the outer regions about 30 Myr ago, it is going on near the centre with full vigour. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tropical Cyclones and Their Transformation into Extratropical: Estimates of the Half-Century Trends

Doklady Earth Sciences - Results from an analysis of the frequency of tropical cyclones, the probability of their transformation into extratropical cyclones, and their trends in different oceanic...     

Ground-Based Measurements of the Total Column of Freons in the Atmosphere near St. Petersburg (2009–2017)

The results of the first long-term (2009–2017) ground-based spectroscopic measurements of the total content (TC) of a number of freons in Russia are presented. According to measurements in Peterhof, TCs of CFC-11 and CFC-12 decrease at a rate of ~0.6% per year and TC of HCFC-22 grows at a rate of ~2.7% per year, which is in good agreement with independent measurements. The seasonal course of freon TC in the area of St. Petersburg is registered: highs of CFC-11 and CFC-12 are observed in summer and lows are in late winter and spring. For the HCFC-22 TC, the opposite seasonal course is observed, with a maximum in winter and a minimum in summer.     

The Main Processes and Stages in the Formation of the Unique Sangaredi Deposit of Bauxites (West Africa)

Doklady Earth Sciences - In the course of additional exploration of the lower horizons of the unique Sangaredi deposit in West Africa, nonlaterized deposits of the Sangaredi series of all major...     

Andromeda IV,a solitary gas‐rich dwarf galaxy

Observations are presented of the isolated dwarf irregular galaxy And IV made with the Hubble Space Telescope Advanced Camera for Surveys and the Giant Metrewave Radio Telescope in the 21 cm HI line. We determine the galaxy distance of 7.17 ± 0.31 Mpc using the Tip of Red Giant Branch method. The galaxy has a total blue absolute magnitude of –12.81 mag, linear Holmberg diameter of 1.88 kpc, and an HI ‐disk extending to 8.4 times the optical Holmberg radius. The HI massto‐blue luminosity ratio for And IV amounts 12.9 M_⊙/L_⊙. From the GMRT data we derive the rotation curve for the HI and fit it with different mass models. We find that the data are significantly better fit with an iso‐thermal dark matter halo, than by an NFW halo. We also find that MOND rotation curve provides a very poor fit to the data. The fact that the isothermal dark matter halo provides the best fit to the data supports models in which star formation feedback results in the formation of a dark matter core in dwarf galaxies. The total mass‐to‐blue luminosity ratio of 162 M_⊙/L_⊙ makes And IV among the darkest dIrr galaxies known. However, its baryonic‐to‐dark mass ratio (M_gas + M *)/M_T = 0.11 is close to the average cosmic baryon fraction of 0.15. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)