E. I. Kaisina's research while affiliated with Russian Academy of Sciences and other places

We undertook a search for new nearby dwarf galaxies outside the known groups in the Local Volume using the data on DESI Legacy Imaging Surveys. In a wide sky area of ~5000 square degrees directed toward the Local Void, we found only 12 candidates to nearby low mass galaxies. Almost all of them are classified as irregular or transition type dwarfs. Additionally, we examined areas of the sky exposed with the Hyper Suprime Camera of the Subaru telescope (~700 square degrees) and found nine more candidates to nearby dwarfs. Finally, nine candidates to the Local Volume were selected by us from the Zaritsky's SMUDG catalog that contains 7070 ultra-diffuse objects automatically detected in the whole area of the DESI surveys. We estimated a fraction of quiescent dSph galaxies in the general cosmic field to be less than 10 percent. Используя данные обзора DESI Legacy Imaging Surveys, мы предприняли поиск новых близких карликовых галактик вне известных групп в Местном Объеме. В обширной области неба площадью примерно 5000 квадратных градусов, направленной к Местному Войду, мы нашли только 12 кандидатов в близкие галактики низкой массы. Все они классифицированы как иррегу лярные либо карлики переходного типа. Дополнительно мы обследовали площади неба, снятые телескопом Субару с камерой Hyper Suprime Camera (около 700 кв. град.) и обнаружили еще девять кандидатов в близкие карлики. Наконец, 9 кандидатов в Местный Объем были отобраны нами из каталога Зарицкого (SMUDG), который содержит 7070 ультра-диффузных объектов, найденных автоматически на всей площади обзора DESI. Мы оцениваем долю "спокойных" dSph галактик в общем космическом поле не более 10 процентов.

We undertook a search for new nearby dwarf galaxies outside the known groups in the Local Volume using the data on DESI Legacy Imaging Surveys. In a wide sky area of ~5000 square degrees directed toward the Local Void, we found only 12 candidates to nearby low mass galaxies. Almost all of them are classified as irregular or transition type dwarfs. Additionally, we examined areas of the sky exposed with the Hyper Suprime Camera of the Subaru telescope (~700 square degrees) and found nine more candidates to nearby dwarfs. Finally, nine candidates to the Local Volume were selected by us from the Zaritsky's SMUDG catalog that contains 7070 ultra-diffuse objects automatically detected in the whole area of the DESI surveys. We estimated a fraction of quiescent dSph galaxies in the general cosmic field to be less than 10 percent. Используя данные обзора DESI Legacy Imaging Surveys, мы предприняли поиск новых близких карликовых галактик вне известных групп в Местном Объеме. В обширной области неба площадью примерно 5000 квадратных градусов, направленной к Местному Войду, мы нашли только 12 кандидатов в близкие галактики низкой массы. Все они классифицированы как иррегу лярные либо карлики переходного типа. Дополнительно мы обследовали площади неба, снятые телескопом Субару с камерой Hyper Suprime Camera (около 700 кв. град.) и обнаружили еще девять кандидатов в близкие карлики. Наконец, 9 кандидатов в Местный Объем были отобраны нами из каталога Зарицкого (SMUDG), который содержит 7070 ультра-диффузных объектов, найденных автоматически на всей площади обзора DESI. Мы оцениваем долю "спокойных" dSph галактик в общем космическом поле не более 10 процентов.

We performed a search for faint low-surface-brightness dwarf galaxies around the major spiral galaxy M 101 and in the large rectangular area within SGL = [30–80]° and SGB = [10–37]° spanning a chain of galaxies: M 63, M 51, M 101, and NGC 6503. We based our search on data from DESI Legacy Imaging Surveys. We discovered six new probable dwarf members of the complex. We present a list of 25 prospective members of the M 101 group and estimate the total mass and the total-mass-to- K -band-luminosity ratio of the group as (1.02 ± 0.42)×10 ¹² M ⊙ and (16.0 ± 6.5) M ⊙ / L ⊙ , respectively. We note that the average dark mass-to-luminosity ratio in the groups around M 63, M 51, and M 101 is (12 ± 4) M ⊙ / L ⊙ , which is almost an order of magnitude lower than the global cosmic ratio, (102 ± 5) M ⊙ / L ⊙ .

We performed a search for faint low surface brightness dwarf galaxies around the major spiral galaxy M\,101 and in the large rectangular area within SGL = [30 -- 80]$^{\circ}$, SGB =[10 -- 37]$^{\circ}$ spanning a chain of galaxies: M\,63, M\,51, M\,101, and NGC\,6503, based on the data from DESI Legacy Imaging Surveys. Six new supposed dwarf members of the complex were discovered. We present a list of 25 prospective members of the M\,101 group and estimate the total mass and the total-mass-to-$K$-band luminosity ratio of the group as $(1.02\pm0.42)\times10^{12}~M_{\odot}$ and $(16.0\pm6.5)~M_{\odot}/L_{\odot}$, respectively. We notice that the average dark mass-to-luminosity ratio in the groups around M\,63, M\,51, and M\,101 is $(12\pm4)M_{\odot}/L_{\odot}$ that almost an order of magnitude lower than the global cosmic ratio, $(102\pm5)M_{\odot}/L_{\odot}$.

We undertook a search for new dwarf galaxies in the Leo-I group using the data from the DECaLS digital sky survey. Five new presumed members of this group have been found in a wide vicinity of M 105(NGC 3379). Currently, the group has a population of 83 galaxies, 33 of which have measured radial velocities. More than half of the group members belong to early types with no signs of ongoing star formation. About a quarter of the galaxies are outside the group’s virial radius, Rv = 385 kpc. The presence of multiple systems with a size of about 15 kpc is evident in the group, but there are no noticeable global flat or filamentary substructures. The luminosity function of the group looks to be deficient in galaxies with absolute magnitudes in the interval MB = [ − 18, −15] mag. The M 105 group is characterized by a radial velocity dispersion of 136 km s−1, orbital mass estimate (5.76 ± 1.32) × 1012 M⊙, and the total mass-to-K-band-luminosity ratio (17.8 ± 4.1)M⊙/L⊙. The neighboring group of galaxies around M 66(NGC 3627) has a similar virial radius, 390 kpc, velocity dispersion, 135 km s−1, and total mass-to-luminosity ratio, (15.6 ± 3.9)M⊙/L⊙. Both groups in the Leo constellation are approaching the Local Group with a velocity of about 100 km s−1. In the background of the M 105 group, we noted a group of 6 galaxies with an unusually low virial mass-to-luminosity ratio, MT/LK = (4.1 ± 2.2)M⊙/L⊙.

We undertook a search for new dwarf galaxies in the Leo-I group using the data from the DECaLS digital sky survey. Five new presumed members of this group have been found in a wide vicinity of ${\rm M}\,105 ({\rm NGC}\,3379$). Currently, the group has a population of $83$ galaxies, $33$ of which have measured radial velocities. More than half of the group members belong to early types with no signs of ongoing star formation. About a quarter of the galaxies are outside the group's virial radius, $R_v = 385$~kpc. The presence of multiple systems with a size of about 15~kpc is evident in the group, but there are no noticeable global flat or filamentary substructures. The luminosity function of the group looks to be deficient in galaxies with absolute magnitudes in the interval $M_B = [-18, -15]$ mag. The ${\rm M}\,105$ group is characterized by a radial velocity dispersion of $136$~km~s$^{-1}$, orbital mass estimate $(5.76\pm1.32)\times 10^{12}~M_{\odot}$, and the total mass-to-K-band-luminosity ratio $(17.8\pm4.1) M_\odot/L_\odot$. The neighboring group of galaxies around ${\rm M}\,66 ({\rm NGC}\,3627$) has a similar virial radius, $390$~kpc, velocity dispersion, $135$~km~s$^{-1}$, and total mass-to-luminosity ratio, $(15.6\pm3.9) M_\odot/L_\odot$. Both groups in the Leo constellation are approaching the Local Group with a velocity of about 100~km~s$^{-1}$. In the background of the ${\rm M}\,105$ group, we noted a group of 6 galaxies with an unusually low virial mass-to-luminosity ratio, $M_T/L_K = (4.1\pm2.2) M_\odot/L_\odot$.

We undertook a search for new dwarf galaxies in the vicinity of relatively isolated nearby galaxies with distances $D < 12$ Mpc and stellar masses in the $2\times10^{11}-3\times10^8~M_{\odot}$ interval, using the data from the DESI Legacy Imaging Surveys. Around the 46 considered Local Volume galaxies, $67$ new candidates for satellites of these galaxies were found. About half of them are classified as spheroidal dwarfs of low surface brightness. The new galaxies are included in the Local Volume database (LVGDB), which now contains 1421 objects, being 63% more than the Updated Nearby Galaxy Catalog.

Using a currently most representative sample of 477 late-type galaxies within 11 Mpc of the Milky Way with measured star-formation rates (SFRs) from the far ultraviolet (FUV) and Hα emission line fluxes, we select galaxies with the extreme ratios: SFR(Hα)/SFR(FUV) > 2 and SFR(Hα)/SFR(FUV) < 1/20. Each subsample amounts to ∼5% of the total number and consists of dwarf galaxies with the stellar masses M*/M⊙ = (5.5 − 9.5) dex. In spite of a huge difference in their SFR(Hα) activity on a scale of ∼10 Myr, the temporarily “excited” and temporarily “quiescent” galaxies follow one and the same relation between SFR(FUV) and M* on a scale of ∼100 Myr. Their average specific star-formation rate log [SFR(FUV)/M*] = −10.1 ± 0.1 (yr−1) coinsides with the Hubble parameter log (H0) = −10.14 (yr−1). On a scale of t ∼ 10 Myr, variations of SFR have a moderate flash amplitude of less than 1 order above the main-sequence and a fading amplitude to 2 orders below the average level. In general, both temporarily excited and temporarily quiescent galaxies have almost similar gas fractions as normal main-sequence galaxies, being able to maintain the current rate of star-formation on another Hubble time scale. Ranging the galaxies according to the density contrast produced by the nearest massive neighbor exhibits only a low average excess of SFR caused by tidal interactions.